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 termi-
nal, 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 allo-
cated by new_GetLine(), are returned to the system by cal-
ling 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, specify-
ing 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 dif-
ferent 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 sett-
tings.
^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 char-
acter 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, fol-
lowed 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 com-
mand 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 dif-
ferent 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 com-
pared 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 inter-
prets 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 func-
tion 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 com-
mand 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 follow-
ing 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 print-
able 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 fol-
lowing 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 func-
tion, 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 con-
figuring 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 confi-
guration is a problem. This is particularly true of embedded
software, where there's no filesystem to read a configura-
tion 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 charac-
ters. 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 path-
name 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 prior-
ity, with the contents of app_string being potentially over-
riden 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 speci-
fies 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 comple-
tion 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 char-
acter, 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 cur-
sor, 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. Alterna-
tively, you can do the same with the ^P, and ^N keys, and in
vi command mode you can alternatively use the k and j char-
acters. 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 pro-
vided.
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 environ-
ment 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 nest-
ing level is, is recorded as a comment preceding the line in
the history file. Writing this as a comment allows the his-
tory 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 pro-
vided 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 enter-
ing 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. Ini-
tially 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 identif-
iers 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 his-
tory 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 iden-
tifier.
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 %H0 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 applica-
tion 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 his-
tory 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 func-
tion 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 dis-
carded.
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 his-
tory 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 his-
tory is turned off, no new lines will be added to the his-
tory 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 vari-
able 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 writ-
ten 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 data-
base (terminfo or termcap), in order to determine which spe-
cial 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 termi-
nal 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 any-
thing 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 func-
tion 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 argu-
ments, 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. Chang-
ing 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 sig-
nal 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 pro-
cess 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 fol-
lowing function.
int gl_last_signal(const GetLine *gl);
This returns the numeric code (eg. SIGINT) of the last sig-
nal 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 key-
board 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 con-
trolling 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 cal-
ling 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. Other-
wise 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 cal-
ling program. It can also, however, be used with the
GL_RETURN option, in case you wish to have a way to distin-
guish 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 con-
tain unusable values, then if a terminal information data-
base 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 appropri-
ate for your system, gl_terminal_size() can be used to sup-
ply a different fallback.
The gl_terminal_size() function allows you to query the
current size of the terminal, and install an alternate fall-
back 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 ter-
minal 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 pro-
vided 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 comple-
tion 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 print-
able 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 follow-
ing,
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 vari-
ables are defined, or the program neglects to call setlo-
cale, 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 com-
pose 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 press-
ing 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 gen-
erate escape pairs like this when you use the meta key,
rather than a real meta character, and other emulators usu-
ally have a way to request this behavior, so you can con-
tinue 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 sys-
tem functions, where available. Unfortunately neither ter-
minfo nor termcap were designed to be reentrant, so you
can't safely use the functions of the getline module in mul-
tiple 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)