gl_get_line(3)

NAME
gl_get_line, new_GetLine, del_GetLine, gl_customize_completion, gl_change_terminal, gl_configure_getline, gl_load_history, gl_save_history, gl_group_history, gl_show_history, gl_watch_fd, gl_terminal_size, gl_resize_history, gl_limit_history, gl_clear_history, gl_toggle_history, gl_lookup_history, gl_state_of_history, gl_range_of_history, gl_size_of_history, gl_echo_mode, gl_replace_prompt, gl_prompt_style, gl_ignore_signal, gl_trap_signal, gl_last_signal - allow the user to compose an input line

SYNOPSIS
#include <stdio.h>
#include <libtecla.h>
GetLine *new_GetLine(size_t linelen, size_t histlen);
GetLine *del_GetLine(GetLine *gl);
char *gl_get_line(GetLine *gl, const char *prompt,
                 const char *start_line, int start_pos);
int gl_customize_completion(GetLine *gl, void *data,
                            CplMatchFn *match_fn);
int gl_change_terminal(GetLine *gl, FILE *input_fp,
                       FILE *output_fp, const char *term);
int gl_configure_getline(GetLine *gl,
                         const char *app_string,
                         const char *app_file,
                         const char *user_file);
int gl_save_history(GetLine *gl, const char *filename,
                    const char *comment, int max_lines);
int gl_load_history(GetLine *gl, const char *filename,
                    const char *comment);
int gl_watch_fd(GetLine *gl, int fd, GlFdEvent event,
                GlFdEventFn *callback, void *data);
int gl_group_history(GetLine *gl, unsigned stream);
int gl_show_history(GetLine *gl, FILE *fp,
                    const char *fmt, int all_groups,
                    int max_lines);
int gl_resize_history(GetLine *gl, size_t bufsize);
void gl_limit_history(GetLine *gl, int max_lines);
void gl_clear_history(GetLine *gl, int all_groups);
void gl_toggle_history(GetLine *gl, int enable);
GlTerminalSize gl_terminal_size(GetLine *gl,
                                int def_ncolumn,
                                int def_nline);
int gl_lookup_history(GetLine *gl, unsigned long id,
                      GlHistoryLine *hline);
void gl_state_of_history(GetLine *gl,
                         GlHistoryState *state);
void gl_range_of_history(GetLine *gl,
                         GlHistoryRange *range);
void gl_size_of_history(GetLine *gl, GlHistorySize *size);
void gl_echo_mode(GetLine *gl, int enable);
void gl_replace_prompt(GetLine *gl, const char *prompt);
void gl_prompt_style(GetLine *gl, GlPromptStyle style);
int gl_ignore_signal(GetLine *gl, int signo);
int gl_trap_signal(GetLine *gl, int signo, unsigned flags,
                   GlAfterSignal after, int errno_value);
int gl_last_signal(const GetLine *gl);

DESCRIPTION
The gl_get_line() function is part of the tecla library (see the libtecla(3) man page). If the user is typing at a terminal, it prompts them for an line of input, then provides interactive editing facilities, similar to those of the unix tcsh shell. In addition to simple command-line editing, it supports recall of previously entered command lines, TAB completion of file names, and in-line wild-card expansion of filenames.

AN EXAMPLE
The following shows a complete example of how to use the gl_get_line() function to get input from the user:
  #include <stdio.h>
  #include <locale.h>
  #include <libtecla.h>
  int main(int argc, char *argv[])
  {
    char *line;    /* The line that the user typed */
    GetLine *gl;   /* The gl_get_line() resource object */
    setlocale(LC_CTYPE, ""); /* Adopt the user's choice */
                             /* of character set. */
    gl = new_GetLine(1024, 2048);
    if(!gl)
      return 1;
    while((line=gl_get_line(gl, "$ ", NULL, -1)) != NULL &&
           strcmp(line, "exit\n") != 0)
      printf("You typed: %s\n", line);
    gl = del_GetLine(gl);
    return 0;
  }

In the example, first the resources needed by the gl_get_line() function are created by calling new_GetLine(). This allocates the memory used in subsequent calls to the gl_get_line() function, including the history buffer for recording previously entered lines. Then one or more lines are read from the user, until either an error occurs, or the user types exit. Then finally the resources that were allocated by new_GetLine(), are returned to the system by calling del_GetLine(). Note the use of the NULL return value of del_GetLine() to make gl NULL. This is a safety precaution. If the program subsequently attempts to pass gl to gl_get_line(), said function will complain, and return an error, instead of attempting to use the deleted resource object.

THE FUNCTIONS USED IN THE EXAMPLE
The descriptions of the functions used in the example are as follows:

  GetLine *new_GetLine(size_t linelen, size_t histlen)

This function creates the resources used by the gl_get_line() function and returns an opaque pointer to the object that contains them. The maximum length of an input line is specified via the linelen argument, and the number of bytes to allocate for storing history lines is set by the histlen argument. History lines are stored back-to-back in a single buffer of this size. Note that this means that the number of history lines that can be stored at any given time, depends on the lengths of the individual lines. If you want to place an upper limit on the number of lines that can be stored, see the gl_limit_history() function described later. If you don't want history at all, specify histlen as zero, and no history buffer will be allocated.

On error, a message is printed to stderr and NULL is returned.

  GetLine *del_GetLine(GetLine *gl)

This function deletes the resources that were returned by a previous call to new_GetLine(). It always returns NULL (ie a deleted object). It does nothing if the gl argument is NULL.

  char *gl_get_line(GetLine *gl, const char *prompt,
                   const char *start_line, int start_pos);

The gl_get_line() function can be called any number of times to read input from the user. The gl argument must have been previously returned by a call to new_GetLine(). The prompt argument should be a normal NUL terminated string, specifying the prompt to present the user with. By default prompts are displayed literally, but if enabled with the gl_prompt_style() function (see later), prompts can contain directives to do underlining, switch to and from bold fonts, or turn highlighting on and off. If you want to specify the initial contents of the line, for the user to edit, pass the desired string via the start_line argument. You can then specify which character of this line the cursor is initially positioned over, using the start_pos argument. This should be -1 if you want the cursor to follow the last character of the start line. If you don't want to preload the line in this manner, send start_line as NULL, and set start_pos to -1. The gl_get_line() function returns a pointer to the line entered by the user, or NULL on error or at the end of the input. The returned pointer is part of the specified gl resource object, and thus should not be free'd by the caller, or assumed to be unchanging from one call to the next. When reading from a user at a terminal, there will always be a newline character at the end of the returned line. When standard input is being taken from a pipe or a file, there will similarly be a newline unless the input line was too long to store in the internal buffer. In the latter case you should call gl_get_line() again to read the rest of the line. Note that this behavior makes gl_get_line() similar to fgets(). In fact when stdin isn't connected to a terminal,gl_get_line() just calls fgets().

OPTIONAL PROMPT FORMATTING
Whereas by default the prompt string that you specify is displayed literally, without any special interpretation of the characters within it, the gl_prompt_style() function can be used to enable optional formatting directives within the prompt.

  void gl_prompt_style(GetLine *gl, GlPromptStyle style);

The style argument, which specifies the formatting style, can take any of the following values:

  GL_FORMAT_PROMPT   -  In this style, the formatting
                        directives described below, when
                        included in prompt strings, are
                        interpreted as follows:
                          %B  -  Display subsequent
                                 characters with a bold
                                 font.
                          %b  -  Stop displaying characters
                                 with the bold font.
                          %F  -  Make subsequent characters
                                 flash.
                          %f  -  Turn off flashing
                                 characters.
                          %U  -  Underline subsequent
                                 characters.
                          %u  -  Stop underlining
                                 characters.
                          %P  -  Switch to a pale (half
                                 brightness) font.
                          %p  -  Stop using the pale font.
                          %S  -  Highlight subsequent
                                 characters (also known as
                                 standout mode).
                          %s  -  Stop highlighting
                                 characters.
                          %V  -  Turn on reverse video.
                          %v  -  Turn off reverse video.
                          %%  -  Display a single %
                                 character.
                        For example, in this mode, a prompt
                        string like "%UOK%u$ " would
                        display the prompt "OK$ ",
                        but with the OK part
                        underlined.
                        Note that although a pair of
                        characters that starts with a %
                        character, but doesn't match any of
                        the above directives is displayed
                        literally, if a new directive is
                        subsequently introduced which does
                        match, the displayed prompt will
                        change, so it is better to always
                        use %% to display a literal %.
                        Also note that not all terminals
                        support all of these text
                        attributes, and that some substitute
                        a different attribute for missing
                        ones.
  GL_LITERAL_PROMPT  -  In this style, the prompt string is
                        printed literally. This is the
                        default style.

THE AVAILABLE KEY BINDING FUNCTIONS
The gl_get_line() function provides a number of functions which can be bound to key sequences. The names of these functions, and what they do, are given below.
  user-interrupt           -  Send a SIGINT signal to the
                              parent process.
  abort                    -  Send a SIGABRT signal to the
                              parent process.
  suspend                  -  Suspend the parent process.
  stop-output              -  Pause terminal output.
  start-output             -  Resume paused terminal output.
  literal-next             -  Arrange for the next character
                              to be treated as a normal
                              character. This allows control
                              characters to be entered.
  cursor-right             -  Move the cursor one character
                              right.
  cursor-left              -  Move the cursor one character
                              left.
  insert-mode              -  Toggle between insert mode and
                              overwrite mode.
  beginning-of-line        -  Move the cursor to the
                              beginning of the line.
  end-of-line              -  Move the cursor to the end of
                              the line.
  delete-line              -  Delete the contents of the
                              current line.
  kill-line                -  Delete everything that follows
                              the cursor.
  backward-kill-line       -  Delete all characters between
                              the cursor and the start of the
                              line.
  forward-word             -  Move to the end of the word
                              which follows the cursor.
  forward-to-word          -  Move the cursor to the start of
                              the word that follows the
                              cursor.
  backward-word            -  Move to the start of the word
                              which precedes the cursor.
  goto-column              -  Move the cursor to the
                              1-relative column in the line
                              specified by any preceding
                              digit-argument sequences (see
                              ENTERING REPEAT COUNTS below).
  find-parenthesis         -  If the cursor is currently
                              over a parenthesis character,
                              move it to the matching
                              parenthesis character. If not
                              over a parenthesis character
                              move right to the next close
                              parenthesis.
  forward-delete-char      -  Delete the character under the
                              cursor.
  backward-delete-char     -  Delete the character which
                              precedes the cursor.
  list-or-eof              -  This is intended for binding
                              to ^D. When invoked when the
                              cursor is within the line it
                              displays all possible
                              completions then redisplays
                              the line unchanged. When
                              invoked on an empty line, it
                              signals end-of-input (EOF) to
                              the caller of gl_get_line().
  del-char-or-list-or-eof  -  This is intended for binding
                              to ^D. When invoked when the
                              cursor is within the line it
                              invokes forward-delete-char.
                              When invoked at the end of the
                              line it displays all possible
                              completions then redisplays
                              the line unchanged. When
                              invoked on an empty line, it
                              signals end-of-input (EOF) to
                              the caller of gl_get_line().
  forward-delete-word      -  Delete the word which follows
                              the cursor.
  backward-delete-word     -  Delete the word which precedes
                              the cursor.
  upcase-word              -  Convert all of the characters
                              of the word which follows the
                              cursor, to upper case.
  downcase-word            -  Convert all of the characters
                              of the word which follows the
                              cursor, to lower case.
  capitalize-word          -  Capitalize the word which
                              follows the cursor.
  change-case              -  If the next character is upper
                              case, toggle it to lower case
                              and vice versa.
  redisplay                -  Redisplay the line.
  clear-screen             -  Clear the terminal, then
                              redisplay the current line.
  transpose-chars          -  Swap the character under the
                              cursor with the character just
                              before the cursor.
  set-mark                 -  Set a mark at the position of
                              the cursor.
  exchange-point-and-mark  -  Move the cursor to the last
                              mark that was set, and move
                              the mark to where the cursor
                              used to be.
  kill-region              -  Delete the characters that lie
                              between the last mark that was
                              set, and the cursor.
  copy-region-as-kill      -  Copy the text between the mark
                              and the cursor to the cut
                              buffer, without deleting the
                              original text.
  yank                     -  Insert the text that was last
                              deleted, just before the
                              current position of the cursor.
  append-yank              -  Paste the current contents of
                              the cut buffer, after the
                              cursor.
  up-history               -  Recall the next oldest line
                              that was entered. Note that
                              in vi mode you are left in
                              command mode.
  down-history             -  Recall the next most recent
                              line that was entered. If no
                              history recall session is
                              currently active, the next
                              line from a previous recall
                              session is recalled. Note that
                              in vi mode you are left in
                              command mode.
  history-search-backward  -  Recall the next oldest line
                              who's prefix matches the string
                              which currently precedes the
                              cursor (in vi command-mode the
                              character under the cursor is
                              also included in the search
                              string).  Note that in vi mode
                              you are left in command mode.
  history-search-forward   -  Recall the next newest line
                              who's prefix matches the string
                              which currently precedes the
                              cursor (in vi command-mode the
                              character under the cursor is
                              also included in the search
                              string).  Note that in vi mode
                              you are left in command mode.
  history-re-search-backward -Recall the next oldest line
                              who's prefix matches that
                              established by the last
                              invocation of either
                              history-search-forward or
                              history-search-backward.
  history-re-search-forward - Recall the next newest line
                              who's prefix matches that
                              established by the last
                              invocation of either
                              history-search-forward or
                              history-search-backward.
  complete-word            -  Attempt to complete the
                              incomplete word which
                              precedes the cursor. Unless
                              the host program has customized
                              word completion, filename
                              completion is attempted. In vi
                              commmand mode the character
                              under the cursor is also
                              included in the word being
                              completed, and you are left in
                              vi insert mode.
  expand-filename          -  Within the command line, expand
                              wild cards, tilde expressions
                              and dollar expressions in the
                              filename which immediately
                              precedes the cursor. In vi
                              commmand mode the character
                              under the cursor is also
                              included in the filename being
                              expanded, and you are left in
                              vi insert mode.
  list-glob                -  List any filenames which match
                              the wild-card, tilde and dollar
                              expressions in the filename
                              which immediately precedes the
                              cursor, then redraw the input
                              line unchanged.
  list-history             -  Display the contents of the
                              history list for the current
                              history group. If a repeat
                              count of > 1 is specified,
                              only that many of the most
                              recent lines are displayed.
                              See the "ENTERING REPEAT
                              COUNTS" section.
  read-from-file           -  Temporarily switch to reading
                              input from the file who's
                              name precedes the cursor.
  read-init-files          -  Re-read teclarc configuration
                              files.
  beginning-of-history     -  Move to the oldest line in the
                              history list. Note that in vi
                              mode you are left in command
                              mode.
  end-of-history           -  Move to the newest line in the
                              history list (ie. the current
                              line). Note that in vi mode
                              this leaves you in command
                              mode.
  digit-argument           -  Enter a repeat count for the
                              next key-binding function.
                              For details, see the ENTERING
                              REPEAT COUNTS section.
  newline                  -  Terminate and return the
                              current contents of the
                              line, after appending a
                              newline character. The newline
                              character is normally '\n',
                              but will be the first
                              character of the key-sequence
                              that invoked the newline
                              action, if this happens to be
                              a printable character. If the
                              action was invoked by the
                              '\n' newline character or the
                              '\r' carriage return
                              character, the line is
                              appended to the history
                              buffer.
  repeat-history           -  Return the line that is being
                              edited, then arrange for the
                              next most recent entry in the
                              history buffer to be recalled
                              when gl_get_line() is
                              next called. Repeatedly
                              invoking this action causes
                              successive historical input
                              lines to be re-executed. Note
                              that this action is equivalent
                              to the 'Operate' action in
                              ksh.
  ring-bell                -  Ring the terminal bell, unless
                              the bell has been silenced via
                              the nobeep configuration
                              option (see the THE TECLA
                              CONFIGURATION FILE section).
  forward-copy-char        -  Copy the next character into
                              the cut buffer (NB. use repeat
                              counts to copy more than one).
  backward-copy-char       -  Copy the previous character
                              into the cut buffer.
  forward-copy-word        -  Copy the next word into the cut
                              buffer.
  backward-copy-word       -  Copy the previous word into the
                              cut buffer.
  forward-find-char        -  Move the cursor to the next
                              occurrence of the next
                              character that you type.
  backward-find-char       -  Move the cursor to the last
                              occurrence of the next
                              character that you type.
  forward-to-char          -  Move the cursor to the
                              character just before the next
                              occurrence of the next
                              character that the user types.
  backward-to-char         -  Move the cursor to the
                              character just after the last
                              occurrence before the cursor
                              of the next character that the
                              user types.
  repeat-find-char         -  Repeat the last
                              backward-find-char,
                              forward-find-char,
                              backward-to-char or
                              forward-to-char.
  invert-refind-char       -  Repeat the last
                              backward-find-char,
                              forward-find-char,
                              backward-to-char, or
                              forward-to-char in the
                              opposite direction.
  delete-to-column         -  Delete the characters from the
                              cursor up to the column that
                              is specified by the repeat
                              count.
  delete-to-parenthesis    -  Delete the characters from the
                              cursor up to and including
                              the matching parenthesis, or
                              next close parenthesis.
  forward-delete-find      -  Delete the characters from the
                              cursor up to and including the
                              following occurence of the
                              next character typed.
  backward-delete-find     -  Delete the characters from the
                              cursor up to and including the
                              preceding occurence of the
                              next character typed.
  forward-delete-to        -  Delete the characters from the
                              cursor up to, but not
                              including, the following
                              occurence of the next
                              character typed.
  backward-delete-to       -  Delete the characters from the
                              cursor up to, but not
                              including, the preceding
                              occurence of the next
                              character typed.
  delete-refind            -  Repeat the last *-delete-find
                              or *-delete-to action.
  delete-invert-refind     -  Repeat the last *-delete-find
                              or *-delete-to action, in the
                              opposite direction.
  copy-to-column           -  Copy the characters from the
                              cursor up to the column that
                              is specified by the repeat
                              count, into the cut buffer.
  copy-to-parenthesis      -  Copy the characters from the
                              cursor up to and including
                              the matching parenthesis, or
                              next close parenthesis, into
                              the cut buffer.
  forward-copy-find        -  Copy the characters from the
                              cursor up to and including the
                              following occurence of the
                              next character typed, into the
                              cut buffer.
  backward-copy-find       -  Copy the characters from the
                              cursor up to and including the
                              preceding occurence of the
                              next character typed, into the
                              cut buffer.
  forward-copy-to          -  Copy the characters from the
                              cursor up to, but not
                              including, the following
                              occurence of the next
                              character typed, into the cut
                              buffer.
  backward-copy-to         -  Copy the characters from the
                              cursor up to, but not
                              including, the preceding
                              occurence of the next
                              character typed, into the cut
                              buffer.
  copy-refind              -  Repeat the last *-copy-find
                              or *-copy-to action.
  copy-invert-refind       -  Repeat the last *-copy-find
                              or *-copy-to action, in the
                              opposite direction.
  vi-mode                  -  Switch to vi mode from emacs
                              mode.
  emacs-mode               -  Switch to emacs mode from vi
                              mode.
  vi-insert                -  From vi command mode, switch to
                              insert mode.
  vi-overwrite             -  From vi command mode, switch to
                              overwrite mode.
  vi-insert-at-bol         -  From vi command mode, move the
                              cursor to the start of the line
                              and switch to insert mode.
  vi-append-at-eol         -  From vi command mode, move the
                              cursor to the end of the line
                              and switch to append mode.
  vi-append                -  From vi command mode, move the
                              cursor one position right, and
                              switch to insert mode.
  vi-replace-char          -  From vi command mode, replace
                              the character under the cursor
                              with the the next character
                              entered.
  vi-forward-change-char   -  From vi command mode, delete
                              the next character then enter
                              insert mode.
  vi-backward-change-char  -  From vi command mode, delete
                              the preceding character then
                              enter insert mode.
  vi-forward-change-word   -  From vi command mode, delete
                              the next word then enter
                              insert mode.
  vi-backward-change-word  -  From vi command mode, delete
                              the preceding word then
                              enter insert mode.
  vi-change-rest-of-line   -  From vi command mode, delete
                              from the cursor to the end of
                              the line, then enter insert
                              mode.
  vi-change-line           -  From vi command mode, delete
                              the current line, then enter
                              insert mode.
  vi-change-to-bol         -  From vi command mode, delete
                              all characters between the
                              cursor and the beginning of
                              the line, then enter insert
                              mode.
  vi-change-to-column      -  From vi command mode, delete
                              the characters from the cursor
                              up to the column that is
                              specified by the repeat count,
                              then enter insert mode.
  vi-change-to-parenthesis -  Delete the characters from the
                              cursor up to and including
                              the matching parenthesis, or
                              next close parenthesis, then
                              enter vi insert mode.
  vi-forward-change-find   -  From vi command mode, delete
                              the characters from the
                              cursor up to and including the
                              following occurence of the
                              next character typed, then
                              enter insert mode.
  vi-backward-change-find  -  From vi command mode, delete
                              the characters from the
                              cursor up to and including the
                              preceding occurence of the
                              next character typed, then
                              enter insert mode.
  vi-forward-change-to     -  From vi command mode, delete
                              the characters from the
                              cursor up to, but not
                              including, the following
                              occurence of the next
                              character typed, then enter
                              insert mode.
  vi-backward-change-to    -  From vi command mode, delete
                              the characters from the
                              cursor up to, but not
                              including, the preceding
                              occurence of the next
                              character typed, then enter
                              insert mode.
  vi-change-refind         -  Repeat the last
                              vi-*-change-find or
                              vi-*-change-to action.
  vi-change-invert-refind  -  Repeat the last
                              vi-*-change-find or
                              vi-*-change-to action, in the
                              opposite direction.
  vi-undo                  -  In vi mode, undo the last
                              editing operation.
  vi-repeat-change         -  In vi command mode, repeat the
                              last command that modified the
                              line.

DEFAULT KEY BINDINGS IN EMACS MODE
The following default key bindings, which can be overriden by the tecla configuration file, are designed to mimic most of the bindings of the unix tcsh shell, when it is in emacs editing mode.

This is the default editing mode of the tecla library.

Note that a key sequence like ^A or C-a means hold the control-key down while pressing the letter A, and that where you see \E or M- in a binding, this represents the escape key or the Meta modifier key. Also note that to gl_get_line(), pressing the escape key before a key is equivalent to pressing the meta key at the same time as that key. Thus the key sequence M-p can be typed in two ways, by pressing the escape key, followed by pressing p, or by pressing the Meta key at the same time as p.

Under UNIX the terminal driver sets a number of special keys for certain functions. The tecla library attempts to use the same keybindings to maintain consistency. The key sequences shown for the following 6 bindings are thus just examples of what they will probably be set to. If you have used the stty command to change these keys, then the default bindings should match.
  ^C     ->   user-interrupt
  ^\     ->   abort
  ^Z     ->   suspend
  ^Q     ->   start-output
  ^S     ->   stop-output
  ^V     ->   literal-next
The cursor keys are refered to by name, as follows. This is necessary because different types of terminals generate different key sequences when their cursor keys are pressed.
  right -> cursor-right
  left -> cursor-left
  up -> up-history
  down -> down-history The remaining bindings don't depend on the terminal setttings.
  ^F     ->   cursor-right
  ^B     ->   cursor-left
  M-i    ->   insert-mode
  ^A     ->   beginning-of-line
  ^E     ->   end-of-line
  ^U     ->   delete-line
  ^K     ->   kill-line
  M-f    ->   forward-word
  M-b    ->   backward-word
  ^D     ->   del-char-or-list-or-eof
  ^H     ->   backward-delete-char
  ^?     ->   backward-delete-char
  M-d    ->   forward-delete-word
  M-^H   ->   backward-delete-word
  M-^?   ->   backward-delete-word
  M-u    ->   upcase-word
  M-l    ->   downcase-word
  M-c    ->   capitalize-word
  ^R     ->   redisplay
  ^L     ->   clear-screen
  ^T     ->   transpose-chars
  ^@     ->   set-mark
  ^X^X   ->   exchange-point-and-mark
  ^W     ->   kill-region
  M-w    ->   copy-region-as-kill
  ^Y     ->   yank
  ^P     ->   up-history
  ^N     ->   down-history
  M-p    ->   history-search-backward
  M-n    ->   history-search-forward
  ^I     ->   complete-word
  ^X*    ->   expand-filename
  ^X^F   ->   read-from-file
  ^X^R   ->   read-init-files
  ^Xg    ->   list-glob
  ^Xh    ->   list-history
  M-<    ->   beginning-of-history
  M->    ->   end-of-history
  \n     ->   newline
  \r     ->   newline
  M-o    ->   repeat-history
  M-^V   ->   vi-mode
  M-0, M-1, ... M-9  ->  digit-argument  (see below)
Note that ^I is what the TAB key generates, and that ^@ can be generated not only by pressing the control key and the @ key simultaneously, but also by pressing the control key and the space bar at the same time.

DEFAULT KEY BINDINGS IN VI MODE
The following default key bindings are designed to mimic the vi style of editing as closely as possible. This means that very few editing functions are provided in the initial character input mode, editing functions instead being provided by the vi command mode. Vi command mode is entered whenever the escape character is pressed, or whenever a key-sequence that starts with a meta character is entered. In addition to mimicing vi, libtecla provides bindings for tab completion, wild-card expansion of file names, and historical line recall.

To learn how to tell the tecla library to use vi mode instead of the default emacs editing mode, see the section entitled THE TECLA CONFIGURATION FILE.

As already mentioned above in the emacs section, Note that a key sequence like ^A or C-a means hold the control-key down while pressing the letter A, and that where you see \E or M- in a binding, this represents the escape key or the Meta modifier key. Also note that to gl_get_line(), pressing the escape key before a key is equivalent to pressing the meta key at the same time as that key. Thus the key sequence M-p can be typed in two ways, by pressing the escape key, followed by pressing p, or by pressing the Meta key at the same time as p.

Under UNIX the terminal driver sets a number of special keys for certain functions. The tecla library attempts to use the same keybindings to maintain consistency, binding them both in input mode and in command mode. The key sequences shown for the following 6 bindings are thus just examples of what they will probably be set to. If you have used the stty command to change these keys, then the default bindings should match.
  ^C     ->   user-interrupt
  ^\     ->   abort
  ^Z     ->   suspend
  ^Q     ->   start-output
  ^S     ->   stop-output
  ^V     ->   literal-next
  M-^C   ->   user-interrupt
  M-^\   ->   abort
  M-^Z   ->   suspend
  M-^Q   ->   start-output
  M-^S   ->   stop-output
Note that above, most of the bindings are defined twice, once as a raw control code like ^C and then a second time as a meta character like M-^C. The former is the binding for vi input mode, whereas the latter is the binding for vi command mode. Once in command mode all key-sequences that the user types that they don't explicitly start with an escape or a meta key, have their first key secretly converted to a meta character before the key sequence is looked up in the key binding table. Thus, once in command mode, when you type the letter i, for example, the tecla library actually looks up the binding for M-i. The cursor keys are refered to by name, as follows. This is necessary because different types of terminals generate different key sequences when their cursor keys are pressed.
  right -> cursor-right
  left -> cursor-left
  up -> up-history
  down -> down-history The cursor keys normally generate a keysequence that start with an escape character, so beware that using the arrow keys will put you into command mode (if you aren't already in command mode).

The following are the terminal-independent key bindings for vi input mode.
  ^D     ->   list-or-eof
  ^G     ->   list-glob
  ^H     ->   backward-delete-char
  ^I     ->   complete-word
  \r     ->   newline
  \n     ->   newline
  ^L     ->   clear-screen
  ^N     ->   down-history
  ^P     ->   up-history
  ^R     ->   redisplay
  ^U     ->   backward-kill-line
  ^W     ->   backward-delete-word
  ^X*    ->   expand-filename
  ^X^F   ->   read-from-file
  ^X^R   ->   read-init-files
  ^?     ->   backward-delete-char
The following are the key bindings that are defined in vi command mode, this being specified by them all starting with a meta character. As mentioned above, once in command mode the initial meta character is optional. For example, you might enter command mode by typing Esc, and then press h twice to move the cursor two positions to the left. Both h characters get quietly converted to M-h before being compared to the key-binding table, the first one because Escape followed by a character is always converted to the equivalent meta character, and the second because command mode was already active.
  M-\     ->   cursor-right     (Meta-space)
  M-$     ->   end-of-line
  M-*     ->   expand-filename
  M-+     ->   down-history
  M--     ->   up-history
  M-<     ->   beginning-of-history
  M->     ->   end-of-history
  M-^     ->   beginning-of-line
  M-;     ->   repeat-find-char
  M-,     ->   invert-refind-char
  M-|     ->   goto-column
  M-~     ->   change-case
  M-.     ->   vi-repeat-change
  M-%     ->   find-parenthesis
  M-a     ->   vi-append
  M-A     ->   vi-append-at-eol
  M-b     ->   backward-word
  M-B     ->   backward-word
  M-C     ->   vi-change-rest-of-line
  M-cb    ->   vi-backward-change-word
  M-cB    ->   vi-backward-change-word
  M-cc    ->   vi-change-line
  M-ce    ->   vi-forward-change-word
  M-cE    ->   vi-forward-change-word
  M-cw    ->   vi-forward-change-word
  M-cW    ->   vi-forward-change-word
  M-cF    ->   vi-backward-change-find
  M-cf    ->   vi-forward-change-find
  M-cT    ->   vi-backward-change-to
  M-ct    ->   vi-forward-change-to
  M-c;    ->   vi-change-refind
  M-c,    ->   vi-change-invert-refind
  M-ch    ->   vi-backward-change-char
  M-c^H   ->   vi-backward-change-char
  M-c^?   ->   vi-backward-change-char
  M-cl    ->   vi-forward-change-char
  M-c\    ->   vi-forward-change-char  (Meta-c-space)
  M-c^    ->   vi-change-to-bol
  M-c0    ->   vi-change-to-bol
  M-c$    ->   vi-change-rest-of-line
  M-c|    ->   vi-change-to-column
  M-c%    ->   vi-change-to-parenthesis
  M-dh    ->   backward-delete-char
  M-d^H   ->   backward-delete-char
  M-d^?   ->   backward-delete-char
  M-dl    ->   forward-delete-char
  M-d     ->   forward-delete-char    (Meta-d-space)
  M-dd    ->   delete-line
  M-db    ->   backward-delete-word
  M-dB    ->   backward-delete-word
  M-de    ->   forward-delete-word
  M-dE    ->   forward-delete-word
  M-dw    ->   forward-delete-word
  M-dW    ->   forward-delete-word
  M-dF    ->   backward-delete-find
  M-df    ->   forward-delete-find
  M-dT    ->   backward-delete-to
  M-dt    ->   forward-delete-to
  M-d;    ->   delete-refind
  M-d,    ->   delete-invert-refind
  M-d^    ->   backward-kill-line
  M-d0    ->   backward-kill-line
  M-d$    ->   kill-line
  M-D     ->   kill-line
  M-d|    ->   delete-to-column
  M-d%    ->   delete-to-parenthesis
  M-e     ->   forward-word
  M-E     ->   forward-word
  M-f     ->   forward-find-char
  M-F     ->   backward-find-char
  M--     ->   up-history
  M-h     ->   cursor-left
  M-H     ->   beginning-of-history
  M-i     ->   vi-insert
  M-I     ->   vi-insert-at-bol
  M-j     ->   down-history
  M-J     ->   history-search-forward
  M-k     ->   up-history
  M-K     ->   history-search-backward
  M-l     ->   cursor-right
  M-L     ->   end-of-history
  M-n     ->   history-re-search-forward
  M-N     ->   history-re-search-backward
  M-p     ->   append-yank
  M-P     ->   yank
  M-r     ->   vi-replace-char
  M-R     ->   vi-overwrite
  M-s     ->   vi-forward-change-char
  M-S     ->   vi-change-line
  M-t     ->   forward-to-char
  M-T     ->   backward-to-char
  M-u     ->   vi-undo
  M-w     ->   forward-to-word
  M-W     ->   forward-to-word
  M-x     ->   forward-delete-char
  M-X     ->   backward-delete-char
  M-yh    ->   backward-copy-char
  M-y^H   ->   backward-copy-char
  M-y^?   ->   backward-copy-char
  M-yl    ->   forward-copy-char
  M-y\    ->   forward-copy-char  (Meta-y-space)
  M-ye    ->   forward-copy-word
  M-yE    ->   forward-copy-word
  M-yw    ->   forward-copy-word
  M-yW    ->   forward-copy-word
  M-yb    ->   backward-copy-word
  M-yB    ->   backward-copy-word
  M-yf    ->   forward-copy-find
  M-yF    ->   backward-copy-find
  M-yt    ->   forward-copy-to
  M-yT    ->   backward-copy-to
  M-y;    ->   copy-refind
  M-y,    ->   copy-invert-refind
  M-y^    ->   copy-to-bol
  M-y0    ->   copy-to-bol
  M-y$    ->   copy-rest-of-line
  M-yy    ->   copy-line
  M-Y     ->   copy-line
  M-y|    ->   copy-to-column
  M-y%    ->   copy-to-parenthesis
  M-^E    ->   emacs-mode
  M-^H    ->   cursor-left
  M-^?    ->   cursor-left
  M-^L    ->   clear-screen
  M-^N    ->   down-history
  M-^P    ->   up-history
  M-^R    ->   redisplay
  M-^D    ->   list-or-eof
  M-^I    ->   complete-word
  M-\r    ->   newline
  M-\n    ->   newline
  M-^X^R  ->   read-init-files
  M-^Xh   ->   list-history
  M-0, M-1, ... M-9  ->  digit-argument  (see below)
Note that ^I is what the TAB key generates.

ENTERING REPEAT COUNTS
Many of the key binding functions described previously, take an optional count, typed in before the target keysequence. This is interpreted as a repeat count by most bindings. A notable exception is the goto-column binding, which interprets the count as a column number.

By default you can specify this count argument by pressing the meta key while typing in the numeric count. This relies on the digit-argument action being bound to Meta-0, Meta-1 etc. Once any one of these bindings has been activated, you can optionally take your finger off the meta key to type in the rest of the number, since every numeric digit thereafter is treated as part of the number, unless it is preceded by the literal-next binding. As soon as a non-digit, or literal digit key is pressed the repeat count is terminated and either causes the just typed character to be added to the line that many times, or causes the next key-binding function to be given that argument.

For example, in emacs mode, typing:

  M-12a

causes the letter 'a' to be added to the line 12 times, whereas

  M-4M-c

Capitalizes the next 4 words.

In vi command mode the Meta modifier is automatically added to all characters typed in, so to enter a count in vi command-mode, just involves typing in the number, just as at it does in the vi editor itself. So for example, in vi command mode, typing:

  4w2x

moves the cursor four words to the right, then deletes two characters.

You can also bind digit-argument to other key sequences. If these end in a numeric digit, that digit gets appended to the current repeat count. If it doesn't end in a numeric digit, a new repeat count is started with a value of zero, and can be completed by typing in the number, after letting go of the key which triggered the digit-argument action.

THE TECLA CONFIGURATION FILE
By default, the first call to gl_get_line() looks for a file called .teclarc in your home directory (ie. ~/.teclarc). If it finds this file, it reads it, interpreting each line as defining a new key binding or an editing configuration option. Since the emacs keybindings are installed by default, if you want to use the non-default vi editing mode, the most important item to go in this file is the following line:
  edit-mode vi
This will re-configure the default bindings for vi-mode. The complete set of arguments that this command accepts are:

  vi     -  Install key-bindings like those of the vi
            editor.
  emacs  -  Install key-bindings like those of the emacs
            editor. This is the default.
  none   -  Use just the native line editing facilities
            provided by the terminal driver.

To prevent the terminal bell from being rung, such as when an unrecognized control-sequence is typed, place the following line in the configuration file:
  nobeep
An example of a key binding line in the configuration file is the following.
  bind M-[2~ insert-mode
On many keyboards, the above key sequence is generated when one presses the insert key, so with this keybinding, one can toggle between the emacs-mode insert and overwrite modes by hitting one key. One could also do it by typing out the above sequence of characters one by one. As explained above, the M- part of this sequence can be typed either by pressing the escape key before the following key, or by pressing the Meta key at the same time as the following key. Thus if you had set the above key binding, and the insert key on your keyboard didn't generate the above key sequence, you could still type it in either of the following 2 ways.
  1. Hit the escape key momentarily, then press '[', then '2', then
     finally '~'.
  2. Press the meta key at the same time as pressing the '[' key,
     then press '2', then '~'.
If you set a keybinding for a key-sequence that is already bound to a function, the new binding overrides the old one. If in the new binding you omit the name of the new function to bind to the key-sequence, the original binding becomes undefined.

Starting with versions of libtecla later than 1.3.3 it is now possible to bind keysequences that begin with a printable character. Previously key-sequences were required to start with a control or meta character.

Note that the special keywords "up", "down", "left" and "right" refer to the arrow keys, and are thus not treated as keysequences. So, for example, to rebind the up and down arrow keys to use the history search mechanism instead of the simple history recall method, you could place the following in your configuration file:
  bind up history-search-backwards
  bind down history-search-backwards

To unbind an existing binding, you can do this with the bind command by omitting to name any action to rebind the key sequence to. For example, by not specifying an action function, the following command unbinds the default beginning-of-line action from the ^A key sequence:
  bind ^A

ALTERNATE CONFIGURATION SOURCES
As mentioned above, by default users have the option of configuring the behavior of gl_get_line() via a configuration file called .teclarc in their home directories. The fact that all applications share this same configuration file is both an advantage and a disadvantage. In most cases it is an advantage, since it encourages uniformity, and frees the user from having to configure each application separately. In some applications, however, this single means of configuration is a problem. This is particularly true of embedded software, where there's no filesystem to read a configuration file from, and also in applications where a radically different choice of keybindings is needed to emulate a legacy keyboard interface. To cater for such cases, the following function allows the application to control where configuration information is read from.

  int gl_configure_getline(GetLine *gl,
                           const char *app_string,
                           const char *app_file,
                           const char *user_file);

It allows the configuration commands that would normally be read from a user's ~/.teclarc file, to be read from any or none of, a string, an application specific configuration file, and/or a user-specific configuration file. If this function is called before the first call to gl_get_line(), the default behavior of reading ~/.teclarc on the first call to gl_get_line() is disabled, so all configuration must be achieved using the configuration sources specified with this function. If app_string != NULL, then it is interpreted as a string containing one or more configuration commands, separated from each other in the string by embedded newline characters. If app_file != NULL then it is interpreted as the full pathname of an application-specific configuration file. If user_file != NULL then it is interpreted as the full pathname of a user-specific configuration file, such as ~/.teclarc. For example, in the following call,
  gl_configure_getline(gl, "edit-mode vi \n nobeep",
                        "/usr/share/myapp/teclarc",
                        "~/.teclarc"); the app_string argument causes the calling application to start in vi edit-mode, instead of the default emacs mode, and turns off the use of the terminal bell by the library. It then attempts to read system-wide configuration commands from an optional file called /usr/share/myapp/teclarc, then finally reads user-specific configuration commands from an optional .teclarc file in the user's home directory. Note that the arguments are listed in ascending order of priority, with the contents of app_string being potentially overriden by commands in app_file, and commands in app_file potentially being overriden by commands in user_file.

You can call this function as many times as needed, the results being cumulative, but note that copies of any filenames specified via the app_file and user_file arguments are recorded internally for subsequent use by the read-init-files key-binding function, so if you plan to call this function multiple times, be sure that the last call specifies the filenames that you want re-read when the user requests that the configuration files be re-read.

FILENAME AND TILDE COMPLETION
With the default key bindings, pressing the TAB key (aka. ^I) results in gl_get_line() attempting to complete the incomplete filename that precedes the cursor. gl_get_line() searches backwards from the cursor, looking for the start of the filename, stopping when it hits either a space or the start of the line. If more than one file has the specified prefix, gl_get_line() completes the filename up to the point at which the ambiguous matches start to differ, then lists the possible matches.

In addition to literally written filenames, gl_get_line() can complete files that start with ~/ and ~user/ expressions and that contain $envvar expressions. In particular, if you hit TAB within an incomplete ~user, expression, gl_get_line() will attempt to complete the username, listing any ambiguous matches.

The completion binding is implemented using the cpl_word_completions() function, which is also available separately to users of this library. See the cpl_word_completions(3) man page for more details.

CUSTOMIZED WORD COMPLETION
If in your application, you would like to have TAB completion complete other things in addition to or instead of filenames, you can arrange this by registering an alternate completion callback function, via a call to the gl_customize_completion() function.

  int gl_customize_completion(GetLine *gl, void *data,
                              CplMatchFn *match_fn);

The data argument provides a way for your application to pass arbitrary, application-specific information to the callback function. This is passed to the callback every time that it is called. It might for example, point to the symbol table from which possible completions are to be sought. The match_fn argument specifies the callback function to be called. The CplMatchFn function type is defined in libtecla.h, as is a CPL_MATCH_FN() macro that you can use to declare and prototype callback functions. The declaration and responsibilities of callback functions are described in depth in the cpl_complete_word(3) man page.

In brief, the callback function is responsible for looking backwards in the input line, back from the point at which the user pressed TAB, to find the start of the word being completed. It then must lookup possible completions of this word, and record them one by one in the WordCompletion object that is passed to it as an argument, by calling the cpl_add_completion() function. If the callback function wishes to provide filename completion in addition to its own specific completions, it has the option of itself calling the builtin file-name completion callback. This also, is documented in the cpl_complete_word(3) man page.

Note that if you would like gl_get_line() to return the current input line when a successful completion is been made, you can arrange this when you call cpl_add_completion(), by making the last character of the continuation suffix a newline character. If you do this, the input line will be updated to display the completion, together with any contiuation suffix up to the newline character, then gl_get_line() will return this input line.

FILENAME EXPANSION
With the default key bindings, pressing ^X* causes gl_get_line() to expand the filename that precedes the cursor, replacing ~/ and ~user/ expressions with the corresponding home directories, and replacing $envvar expressions with the value of the specified environment variable, then if there are any wildcards, replacing the so far expanded filename with a space-separated list of the files which match the wild cards.

The expansion binding is implemented using the ef_expand_file() function. See the ef_expand_file(3) man page for more details.

RECALLING PREVIOUSLY TYPED LINES
Every time that a new line is entered by the user, it is appended to a list of historical input lines maintained within the GetLine resource object. You can traverse up and down this list using the up and down arrow keys. Alternatively, you can do the same with the ^P, and ^N keys, and in vi command mode you can alternatively use the k and j characters. Thus pressing up-arrow once, replaces the current input line with the previously entered line. Pressing up-arrow again, replaces this with the line that was entered before it, etc.. Having gone back one or more lines into the history list, one can return to newer lines by pressing down-arrow one or more times. If you do this sufficient times, you will return to the original line that you were entering when you first hit up-arrow.

Note that in vi mode, all of the history recall functions switch the library into command mode.

In emacs mode the M-p and M-n keys work just like the ^P and ^N keys, except that they skip all but those historical lines which share the prefix that precedes the cursor. In vi command mode the upper case K and J characters do the same thing, except that the string that they search for includes the character under the cursor as well as what precedes it.

Thus for example, suppose that you were in emacs mode, and you had just entered the following list of commands in the order shown:
  ls ~/tecla/
  cd ~/tecla
  ls -l getline.c
  emacs ~/tecla/getline.c
If you next typed:
  ls
and then hit M-p, then rather than returning the previously typed emacs line, which doesn't start with "ls", gl_get_line() would recall the "ls -l getline.c" line. Pressing M-p again would recall the "ls ~/tecla/" line.

HISTORY FILES
To save the contents of the history buffer before quitting your application, and subsequently restore them when you next start the application, the following functions are provided.

 int gl_save_history(GetLine *gl, const char *filename,
                     const char *comment, int max_lines);
 int gl_load_history(GetLine *gl, const char *filename,
                     const char *comment);

The filename argument specifies the name to give the history file when saving, or the name of an existing history file, when loading. This may contain home-directory and environment variable expressions, such as "~/.myapp_history" or "$HOME/.myapp_history".

Along with each history line, extra information about it, such as when it was entered by the user, and what its nesting level is, is recorded as a comment preceding the line in the history file. Writing this as a comment allows the history file to double as a command file, just in case you wish to replay a whole session using it. Since comment prefixes differ in different languages, the comment argument is provided for specifying the comment prefix. For example, if your application were a unix shell, such as the bourne shell, you would specify "#" here. Whatever you choose for the comment character, you must specify the same prefix to gl_load_history() that you used when you called gl_save_history() to write the history file.

The max_lines must be either -1 to specify that all lines in the history list be saved, or a positive number specifying a ceiling on how many of the most recent lines should be saved.

Both fuctions return non-zero on error, after writing an error message to stderr. Note that gl_load_history() does not consider the non-existence of a file to be an error.

MULTIPLE HISTORY LISTS
If your application uses a single GetLine object for entering many different types of input lines, you may wish gl_get_line() to distinguish the different types of lines in the history list, and only recall lines that match the current type of line. To support this requirement, gl_get_line() marks lines being recorded in the history list with an integer identifier chosen by the application. Initially this identifier is set to 0 by new_GetLine(), but it can be changed subsequently by calling gl_group_history().

  int gl_group_history(GetLine *gl, unsigned id);

The integer identifier id can be any number chosen by the application, but note that gl_save_history() and gl_load_history() preserve the association between identifiers and historical input lines between program invokations, so you should choose fixed identifiers for the different types of input line used by your application.

Whenever gl_get_line() appends a new input line to the history list, the current history identifier is recorded with it, and when it is asked to recall a historical input line, it only recalls lines that are marked with the current identifier.

DISPLAYING HISTORY
The history list can be displayed by calling gl_show_history().

  int gl_show_history(GetLine *gl, FILE *fp,
                      const char *fmt,
                      int all_groups,
                      int max_lines);

This displays the current contents of the history list to the stdio output stream fp. If the max_lines argument is greater than or equal to zero, then no more than this number of the most recent lines will be displayed. If the all_groups argument is non-zero, lines from all history groups are displayed. Otherwise just those of the currently selected history group are displayed. The format string argument, fmt, determines how the line is displayed. This can contain arbitrary characters which are written verbatim, interleaved with any of the following format directives:
  %D  -  The date on which the line was originally
         entered, formatted like 2001-11-20.
  %T  -  The time of day when the line was entered,
         formatted like 23:59:59.
  %N  -  The sequential entry number of the line in
         the history buffer.
  %G  -  The number of the history group which the
         line belongs to.
  %%  -  A literal % character.
  %H  -  The history line itself.
Thus a format string like "%D %T %H would output something like:
  2001-11-20 10:23:34  Hello world
Note the inclusion of an explicit newline character in the format string.

LOOKING UP HISTORY
The gl_lookup_history() function allows the calling application to look up lines in the history list.

  typedef struct {
    const char *line;    /* The requested historical */
                         /*  line. */
    unsigned group;      /* The history group to which */
                         /*  the line belongs. */
    time_t timestamp;    /* The date and time at which */
                         /*  the line was originally */
                         /*  entered. */
  } GlHistoryLine;
  int gl_lookup_history(GetLine *gl, unsigned long id,
                        GlHistoryLine *hline);

The id argument indicates which line to look up, where the first line that was entered in the history list after new_GetLine() was called, is denoted by 0, and subsequently entered lines are denoted with successively higher numbers. Note that the range of lines currently preserved in the history list can be queried by calling the gl_range_of_history() function, described later. If the requested line is in the history list, the details of the line are recorded in the variable pointed to by the hline argument, and 1 is returned. Otherwise 0 is returned, and the variable pointed to by hline is left unchanged.

Beware that the string returned in hline->line is part of the history buffer, so it must not be modified by the caller, and will be recycled on the next call to any function that takes gl as its argument. Therefore you should make a private copy of this string if you need to keep it around.

MISCELLANEOUS HISTORY CONFIGURATION
If you wish to change the size of the history buffer that was originally specified in the call to new_GetLine(), you can do so with the gl_resize_history() function.

  int gl_resize_history(GetLine *gl, size_t histlen);

The histlen argument specifies the new size in bytes, and if you specify this as 0, the buffer will be deleted.

As mentioned in the discussion of new_GetLine(), the number of lines that can be stored in the history buffer, depends on the lengths of the individual lines. For example, a 1000 byte buffer could equally store 10 lines of average length 100 bytes, or 2 lines of average length 50 bytes. Although the buffer is never expanded when new lines are added, a list of pointers into the buffer does get expanded when needed to accomodate the number of lines currently stored in the buffer. To place an upper limit on the number of lines in the buffer, and thus a ceiling on the amount of memory used in this list, you can call the gl_limit_history() function.

  void gl_limit_history(GetLine *gl, int max_lines);

The max_lines should either be a positive number >= 0, specifying an upper limit on the number of lines in the buffer, or be -1 to cancel any previously specified limit. When a limit is in effect, only the max_lines most recently appended lines are kept in the buffer. Older lines are discarded.

To discard lines from the history buffer, use the gl_clear_history() function.

  void gl_clear_history(GetLine *gl, int all_groups);

The all_groups argument tells the function whether to delete just the lines associated with the current history group (see gl_group_history()), or all historical lines in the buffer.

The gl_toggle_history() function allows you to toggle history on and off without losing the current contents of the history list.

  void gl_toggle_history(GetLine *gl, int enable);

Setting the enable argument to 0 turns off the history mechanism, and setting it to 1 turns it back on. When history is turned off, no new lines will be added to the history list, and history lookup key-bindings will act as though there is nothing in the history buffer.

QUERYING HISTORY INFORMATION
The configured state of the history list can be queried with the gl_history_state() function.

  typedef struct {
    int enabled;     /* True if history is enabled */
    unsigned group;  /* The current history group */
    int max_lines;   /* The current upper limit on the */
                     /*  number of lines in the history */
                     /*  list, or -1 if unlimited. */
  } GlHistoryState;
  void gl_state_of_history(GetLine *gl,
                           GlHistoryState *state);

On return, the status information is recorded in the variable pointed to by the state argument.

The gl_range_of_history() function returns the number and range of lines in the history list.

typedef struct {
  unsigned long oldest;  /* The sequential entry number */
                         /*  of the oldest line in the */
                         /*  history list. */
  unsigned long newest;  /* The sequential entry number */
                         /*  of the newest line in the */
                         /*  history list. */
  int nlines;            /* The number of lines in the */
                         /*  history list. */
} GlHistoryRange;
void gl_range_of_history(GetLine *gl, GlHistoryRange *range);

The return values are recorded in the variable pointed to by the range argument. If the nlines member of this structure is greater than zero, then the oldest and newest members report the range of lines in the list, and newest=oldest+nlines-1. Otherwise they are both zero.

The gl_size_of_history() function returns the total size of the history buffer and the amount of the buffer that is currently occupied.

  typedef struct {
    size_t size;      /* The size of the history buffer */
                      /*  (bytes). */
    size_t used;      /* The number of bytes of the */
                      /*  history buffer that are */
                      /*  currently occupied. */
  } GlHistorySize;
  void gl_size_of_history(GetLine *gl, GlHistorySize *size);

On return, the size information is recorded in the variable pointed to by the size argument.

CHANGING TERMINALS
The new_GetLine() constructor function assumes that input is to be read from stdin, and output written to stdout. The following function allows you to switch to different input and output streams.

  int gl_change_terminal(GetLine *gl, FILE *input_fp,
                         FILE *output_fp, const char *term);

The gl argument is the object that was returned by new_GetLine(). The input_fp argument specifies the stream to read from, and output_fp specifies the stream to be written to. Only if both of these refer to a terminal, will interactive terminal input be enabled. Otherwise gl_get_line() will simply call fgets() to read command input. If both streams refer to a terminal, then they must refer to the same terminal, and the type of this terminal must be specified via the term argument. The value of the term argument is looked up in the terminal information database (terminfo or termcap), in order to determine which special control sequences are needed to control various aspects of the terminal. new_GetLine() for example, passes the return value of getenv("TERM") in this argument. Note that if one or both of input_fp and output_fp don't refer to a terminal, then it is legal to pass NULL instead of a terminal type.

Note that if you want to pass file descriptors to gl_change_terminal(), you can do this by creating stdio stream wrappers using the POSIX fdopen() function.

EXTERNAL EVENT HANDLING
While gl_get_line() is waiting for keyboard input from the user, you can ask it to also watch for activity on arbitrary file descriptors, such as network sockets, pipes etc, and have it call functions of your choosing when activity is seen. This works on any system that has the select() system call, which is most, if not all flavors of unix. Registering a file descriptor to be watched by gl_get_line() involves calling the gl_watch_fd() function.

  int gl_watch_fd(GetLine *gl, int fd, GlFdEvent event,
                  GlFdEventFn *callback, void *data);

If this returns non-zero, then it means that either your arguments are invalid, or that this facility isn't supported on the host system.

The fd argument is the file descriptor to be watched. The event argument specifies what type of activity is of interest, chosen from the following enumerated values:

  GLFD_READ   -  Watch for the arrival of data to be read.
  GLFD_WRITE  -  Watch for the ability to write to the file
                 descriptor without blocking.
  GLFD_URGENT -  Watch for the arrival of urgent
                 out-of-band data on the file descriptor.

The callback argument is the function to call when the selected activity is seen. It should be defined with the following macro, which is defined in libtecla.h.

  #define GL_FD_EVENT_FN(fn) GlFdStatus (fn)(GetLine *gl, \
                                      void *data, int fd, \
                                      GlFdEvent event)

The data argument of the gl_watch_fd() function is passed to the callback function for its own use, and can point to anything you like, including NULL. The file descriptor and the event argument are also passed to the callback function, and this potentially allows the same callback function to be registered to more than one type of event and/or more than one file descriptor. The return value of the callback function should be one of the following values.

  GLFD_ABORT    -  Tell gl_get_line() to abort with an
                   error (errno won't be set, so set it
                   appropriately yourself if you need it).
  GLFD_REFRESH  -  Redraw the input line then continue
                   waiting for input. Return this if
                   your callback wrote to the terminal.
  GLFD_CONTINUE -  Continue to wait for input, without
                   redrawing the line.

Note that before calling the callback, gl_get_line() blocks most signals, and leaves its own signal handlers installed, so if you need to catch a particular signal you will need to both temporarily install your own signal handler, and unblock the signal. Be sure to re-block the signal (if it was originally blocked) and reinstate the original signal handler, if any, before returning.

Your callback shouldn't try to read from the terminal, which is left in raw mode as far as input is concerned. You can however write to the terminal as usual, since features like conversion of newline to carriage-return/linefeed are re-enabled while the callback is running. If your callback function does write to the terminal, be sure to output a newline first, and when your callback returns, tell gl_get_line() that the input line needs to be redrawn, by returning the GLFD_REFRESH status code.

To remove a callback function that you previously registered for a given file descriptor and event, simply call gl_watch_fd() with the same file descriptor and event arguments, but with a callback argument of 0. The data argument is ignored in this case.

SIGNAL HANDLING DEFAULTS
By default, the gl_get_line() function intercepts a number of signals. This is particularly important for signals which would by default terminate the process, since the terminal needs to be restored to a usable state before this happens. In this section, the signals that are trapped by default, and how gl_get_line() responds to them, is described. Changing these defaults is the topic of the following section.

When the following subset of signals are caught, gl_get_line() first restores the terminal settings and signal handling to how they were before gl_get_line() was called, resends the signal, to allow the calling application's signal handlers to handle it, then if the process still exists, gl_get_line() returns NULL and sets errno as specified below.

 SIGINT  -  This signal is generated both by the keyboard
            interrupt key (usually ^C), and the keyboard
            break key.
            errno=EINTR
 SIGHUP  -  This signal is generated when the controlling
            terminal exits.
            errno=ENOTTY
 SIGPIPE -  This signal is generated when a program attempts
            to write to a pipe who's remote end isn't being
            read by any process. This can happen for example
            if you have called gl_change_terminal() to
            redirect output to a pipe hidden under a pseudo
            terminal.
            errno=EPIPE
 SIGQUIT -  This signal is generated by the keyboard quit
            key (usually ^\).
            errno=EINTR
 SIGABRT -  This signal is generated by the standard C,
            abort() function. By default it both
            terminates the process and generates a core
            dump.
            errno=EINTR
 SIGTERM -  This is the default signal that the UN*X
            kill command sends to processes.
            errno=EINTR

Note that in the case of all of the above signals, POSIX mandates that by default the process is terminated, with the addition of a core dump in the case of the SIGQUIT signal. In other words, if the calling application doesn't override the default handler by supplying its own signal handler, receipt of the corresponding signal will terminate the application before gl_get_line() returns.

If gl_get_line() aborts with errno set to EINTR, you can find out what signal caused it to abort, by calling the following function.

  int gl_last_signal(const GetLine *gl);

This returns the numeric code (eg. SIGINT) of the last signal that was received during the most recent call to gl_get_line(), or -1 if no signals were received.

On systems that support it, when a SIGWINCH (window change) signal is received, gl_get_line() queries the terminal to find out its new size, redraws the current input line to accomodate the new size, then returns to waiting for keyboard input from the user. Unlike other signals, this signal isn't resent to the application.

Finally, the following signals cause gl_get_line() to first restore the terminal and signal environment to that which prevailed before gl_get_line() was called, then resend the signal to the application. If the process still exists after the signal has been delivered, then gl_get_line() then re-establishes its own signal handlers, switches the terminal back to raw mode, redisplays the input line, and goes back to awaiting terminal input from the user.

 SIGCONT    -  This signal is generated when a suspended
               process is resumed.
 SIGPWR     -  This signal is generated when a power failure
               occurs (presumably when the system is on a
               UPS).
 SIGALRM    -  This signal is generated when a timer
               expires.
 SIGUSR1    -  An application specific signal.
 SIGUSR2    -  Another application specific signal.
 SIGVTALRM  -  This signal is generated when a virtual
               timer expires (see man setitimer(2)).
 SIGXCPU    -  This signal is generated when a process
               exceeds its soft CPU time limit.
 SIGTSTP    -  This signal is generated by the terminal
               suspend key, which is usually ^Z, or the
               delayed terminal suspend key, which is
               usually ^Y.
 SIGTTIN    -  This signal is generated if the program
               attempts to read from the terminal while the
               program is running in the background.
 SIGTTOU    -  This signal is generated if the program
               attempts to write to the terminal while the
               program is running in the background.

Obviously not all of the above signals are supported on all systems, so code to support them is conditionally compiled into the tecla library.

Note that if SIGKILL, which by definition can't be caught, or any of the hardware generated exception signals, such as SIGSEGV, SIGBUS and SIGFPE, are received and unhandled while gl_get_line() has the terminal in raw mode, the program will be terminated without the terminal having been restored to a usable state. In practice, job-control shells usually reset the terminal settings when a process relinquishes the controlling terminal, so this is only a problem with older shells.

CUSTOMIZED SIGNAL HANDLING
The previous section listed the signals that gl_get_line() traps by default, and described how it responds to them. This section describes how to both add and remove signals from the list of trapped signals, and how to specify how gl_get_line() should respond to a given signal.

If you don't need gl_get_line() to do anything in response to a signal that it normally traps, you can tell to gl_get_line() to ignore that signal by calling gl_ignore_signal().

  int gl_ignore_signal(GetLine *gl, int signo);

The signo argument is the number of the signal (eg. SIGINT) that you want to have ignored. If the specified signal isn't currently one of those being trapped, this function does nothing.

The gl_trap_signal() function allows you to either add a new signal to the list that gl_get_line() traps, or modify how it responds to a signal that it already traps.

  int gl_trap_signal(GetLine *gl, int signo, unsigned flags,
                     GlAfterSignal after, int errno_value);

The signo argument is the number of the signal that you wish to have trapped. The flags argument is a set of flags which determine the environment in which the application's signal handler is invoked, the after argument tells gl_get_line() what to do after the application's signal handler returns, and errno_value tells gl_get_line() what to set errno to if told to abort.

The flags argument is a bitwise OR of zero or more of the following enumerators:

  GLS_RESTORE_SIG  -  Restore the caller's signal
                      environment while handling the
                      signal.
  GLS_RESTORE_TTY  -  Restore the caller's terminal settings
                      while handling the signal.
  GLS_RESTORE_LINE -  Move the cursor to the start of the
                      line following the input line before
                      invoking the application's signal
                      handler.
  GLS_REDRAW_LINE  -  Redraw the input line when the
                      application's signal handler returns.
  GLS_UNBLOCK_SIG  -  Normally, if the calling program has
                      a signal blocked (man sigprocmask),
                      gl_get_line() does not trap that
                      signal. This flag tells gl_get_line()
                      to trap the signal and unblock it for
                      the duration of the call to
                      gl_get_line().
  GLS_DONT_FORWARD -  If this flag is included, the signal
                      will not be forwarded to the signal
                      handler of the calling program.

Two commonly useful flag combinations are also enumerated as follows:

  GLS_RESTORE_ENV   = GLS_RESTORE_SIG | GLS_RESTORE_TTY |
                      GLS_REDRAW_LINE
  GLS_SUSPEND_INPUT = GLS_RESTORE_ENV | GLS_RESTORE_LINE

If your signal handler, or the default system signal handler for this signal, if you haven't overriden it, never either writes to the terminal, nor suspends or terminates the calling program, then you can safely set the flags argument to 0.

If your signal handler always writes to the terminal, reads from it, or suspends or terminates the program, you should specify the flags argument as GL_SUSPEND_INPUT, so that:

1. The cursor doesn't get left in the middle of the input
   line.
2. So that the user can type in input and have it echoed.
3. So that you don't need to end each output line with
   \r\n, instead of just \n.

The GL_RESTORE_ENV combination is the same as GL_SUSPEND_INPUT, except that it doesn't move the cursor, and if your signal handler doesn't read or write anything to the terminal, the user won't see any visible indication that a signal was caught. This can be useful if you have a signal handler that only occasionally writes to the terminal, where using GL_SUSPEND_LINE would cause the input line to be unnecessarily duplicated when nothing had been written to the terminal. Such a signal handler, when it does write to the terminal, should be sure to start a new line at the start of its first write, by writing a new line before returning. If the signal arrives while the user is entering a line that only occupies a signal terminal line, or if the cursor is on the last terminal line of a longer input line, this will have the same effect as GL_SUSPEND_INPUT. Otherwise it will start writing on a line that already contains part of the displayed input line. This doesn't do any harm, but it looks a bit ugly, which is why the GL_SUSPEND_INPUT combination is better if you know that you are always going to be writting to the terminal.

The after argument, which determines what gl_get_line() does after the application's signal handler returns (if it returns), can take any one of the following values:

  GLS_RETURN   - Return the completed input line, just as
                 though the user had pressed the return
                 key.
  GLS_ABORT    - Cause gl_get_line() to return NULL.
  GLS_CONTINUE - Resume command line editing.

The errno_value argument is intended to be combined with the GLS_ABORT option, telling gl_get_line() what to set the standard errno variable to before returning NULL to the calling program. It can also, however, be used with the GL_RETURN option, in case you wish to have a way to distinguish between an input line that was entered using the return key, and one that was entered by the receipt of a signal.

THE TERMINAL SIZE
On most systems the combination of the TIOCGWINSZ ioctl and the SIGWINCH signal is used to maintain an accurate idea of the terminal size. The terminal size is newly queried every time that gl_get_line() is called and whenever a SIGWINCH signal is received.

On the few systems where this mechanism isn't available, at startup new_GetLine() first looks for the LINES and COLUMNS environment variables. If these aren't found, or they contain unusable values, then if a terminal information database like terminfo or termcap is available, the default size of the terminal is looked up in this database. If this too fails to provide the terminal size, a default size of 80 columns by 24 lines is used. If this default isn't appropriate for your system, gl_terminal_size() can be used to supply a different fallback.

The gl_terminal_size() function allows you to query the current size of the terminal, and install an alternate fallback size for cases where the size isn't available. Beware that the terminal size won't be available if reading from a pipe or a file, so the default values can be important even on systems that do support ways of finding out the terminal size.

  typedef struct {
    int nline;        /* The terminal has nline lines */
    int ncolumn;      /* The terminal has ncolumn columns */
  } GlTerminalSize;
  GlTerminalSize gl_terminal_size(GetLine *gl,
                                  int def_ncolumn,
                                  int def_nline);

This function first updates gl_get_line()'s idea of the terminal size, then records its findings in the return value.

The def_ncolumn and def_nline specify the default number of terminal columns and lines to use if the terminal size can't be determined.

HIDING WHAT YOU TYPE
When entering sensitive information, such as passwords, it is best not to have the text that you are entering echoed on the terminal. Furthermore, such text should not be recorded in the history list, since somebody finding your terminal unattended could then recall it, or somebody snooping through your directories could see it in your history file. With this in mind, the gl_echo_mode() function allows you to toggle on and off the display and archival of any text that is subsequently entered in calls to gl_get_line().

  int gl_echo_mode(GetLine *gl, int enable);

The enable argument specifies whether entered text should be visible or not. If it is 0, then subsequently entered lines will not be visible on the terminal, and will not be recorded in the history list. If it is 1, then subsequent input lines will be displayed as they are entered, and provided that history hasn't been turned off via a call to gl_toggle_history(), then they will also be archived in the history list. Finally, if the enable argument is -1, then the echoing mode is left unchanged, which allows you to non-destructively query the current setting via the return value. In all cases, the return value of the function is 0 if echoing was disabled before the function was called, and 1 if it was enabled.

When echoing is turned off, note that although tab completion will invisibly complete your prefix as far as possible, ambiguous completions will not be displayed.

CALLBACK FUNCTION FACILITIES
Unless otherwise stated, callback functions, such as tab completion callbacks and event callbacks should not call any functions in this module. The following functions, however, are designed specifically to be used by callback functions.

Calling the gl_replace_prompt() function from a callback tells gl_get_line() to display a different prompt when the callback returns. It has no effect if called when gl_get_line() is not being called.

  void gl_replace_prompt(GetLine *gl, const char *prompt);

INTERNATIONAL CHARACTER SETS
Since libtecla version 1.4.0, gl_get_line() has been 8-bit clean. This means that all 8-bit characters that are printable in the user's current locale are now displayed verbatim and included in the returned input line. Assuming that the calling program correctly contains a call like the following,

  setlocale(LC_CTYPE, "");

then the current locale is determined by the first of the environment variables LC_CTYPE, LC_ALL, and LANG, that is found to contain a valid locale name. If none of these variables are defined, or the program neglects to call setlocale, then the default C locale is used, which is US 7-bit ASCII. On most unix-like platforms, you can get a list of valid locales by typing the command:

  locale -a

at the shell prompt.

  Meta keys and locales
Beware that in most locales other than the default C locale, meta characters become printable, and they are then no longer considered to match M-c style key bindings. This allows international characters to be entered with the compose key without unexpectedly triggering meta key bindings. You can still invoke meta bindings, since there are actually two ways to do this. For example the binding M-c can also be invoked by pressing the escape key momentarily, then pressing the c key, and this will work regardless of locale. Moreover, many modern terminal emulators, such as gnome's gnome-terminal's and KDE's konsole terminals, already generate escape pairs like this when you use the meta key, rather than a real meta character, and other emulators usually have a way to request this behavior, so you can continue to use the meta key on most systems.

For example, although xterm terminal emulators generate real 8-bit meta characters by default when you use the meta key, they can be configured to output the equivalent escape pair by setting their EightBitInput X resource to False. You can either do this by placing a line like the following in your ~/.Xdefaults file,

  XTerm*EightBitInput: False

or by starting an xterm with an -xrm '*EightBitInput: False' command-line argument. In recent versions of xterm you can toggle this feature on and off with the "Meta Sends Escape" option in the menu that is displayed when you press the left mouse button and the control key within an xterm window. In CDE, dtterms can be similarly coerced to generate escape pairs in place of meta characters, by setting the Dtterm*KshMode resource to True.

  Entering international characters
If you don't have a keyboard that generates all of the international characters that you need, there is usually a compose key that will allow you to enter special characters, or a way to create one. For example, under X windows on unix-like systems, if your keyboard doesn't have a compose key, you can designate a redundant key to serve this purpose with the xmodmap command. For example, on many PC keyboards there is a microsoft-windows key, which is otherwise useless under Linux. On my PC the xev program reports that pressing this key generates keycode 115, so to turn this key into a compose key, I do the following:

  xmodmap -e 'keycode 115 = Multi_key'

I can then enter an i with a umlaut over it by typing this key, followed by ", followed by i.

THREAD SAFETY
In a multi-threaded program, you should use the libtecla_r.a version of the library. This uses reentrant versions of system functions, where available. Unfortunately neither terminfo nor termcap were designed to be reentrant, so you can't safely use the functions of the getline module in multiple threads (you can use the separate file-expansion and word-completion modules in multiple threads, see the corresponding man pages for details). However due to the use of POSIX reentrant functions for looking up home directories etc, it is safe to use this module from a single thread of a multi-threaded program, provided that your other threads don't use any termcap or terminfo functions.

FILES
libtecla.a      -    The tecla library
libtecla.h      -    The tecla header file.
~/.teclarc      -    The personal tecla customization file.

SEE ALSO
libtecla(3), ef_expand_file(3), cpl_complete_word(3), pca_lookup_file(3)

AUTHOR
Martin Shepherd (mcs@astro.caltech.edu)