Interactive Command-line Input Library Functions
gl_get_line(3TECLA)
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_inactivity_timeout, gl_terminal_size, gl_set_term_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, gl_completion_action,
gl_register_action, gl_display_text, gl_return_status,
gl_error_message, gl_catch_blocked, gl_list_signals,
gl_bind_keyseq, gl_erase_terminal, gl_automatic_history,
gl_append_history, gl_query_char, gl_read_char - allow the
user to compose an input lineSYNOPSIS
cc [ flag... ] file... -ltecla [ library... ]
#include
#include
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_query_char(GetLine *gl, const char *prompt, char defchar);
int gl_read_char(GetLine *gl);
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);
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gl_get_line(3TECLA)
int gl_bind_keyseq(GetLine *gl, GlKeyOrigin origin,
const char *keyseq, const char *action);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_inactivity_timeout(GetLine *gl, GlTimeoutFn *callback,
void *data, unsigned long sec, unsigned long nsec);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_set_term_size(GetLine *gl, int ncolumn, int nline);
int gl_lookup_history(GetLine *gl, unsigned long id,
GlHistoryLine *hline);SunOS 5.11 Last change: 28 Nov 2007 2
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gl_get_line(3TECLA)
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(GetLine *gl);
int gl_completion_action(GetLine *gl, void *data,
CplMatchFn *match_fn, int list_only, const char *name,
const char *keyseq);int gl_register_action(GetLine *gl, void *data, GlActionFn *fn,
const char *name, const char *keyseq);int gl_display_text(GetLine *gl, int indentation,
const char *prefix, const char *suffix, int fill_char,
int def_width, int start, const char *string);
GlReturnStatus gl_return_status(GetLine *gl);
const char *gl_error_message(GetLine *gl, char *buff, size_t n);
void gl_catch_blocked(GetLine *gl);
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gl_get_line(3TECLA)
int gl_list_signals(GetLine *gl, sigset_t *set);
int gl_append_history(GetLine *gl, const char *line);
int gl_automatic_history(GetLine *gl, int enable);
int gl_erase_terminal(GetLine *gl);
DESCRIPTION
The gl_get_line() function is part of the libtecla(3LIB)
library. If the user is typing at a terminal, each call 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 completionof file names, and in-line wild-card expansion of filenames.
Documentation of both the user-level command-line editing
features and all user configuration options can be found on the tecla(5) manual page. An Example The following shows a complete example of how to use thegl_get_line() function to get input from the user:
#include
#include
#include
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; }SunOS 5.11 Last change: 28 Nov 2007 4
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In the example, first the resources needed by thegl_get_line() function are created by calling new_GetLine().
This allocates the memory used in subsequent calls to thegl_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 theuser 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 togl_get_line(), said function will complain, and return an
error, instead of attempting to use the deleted resource object. The Functions Used In The ExampleThe new_GetLine() 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 by the linelen argument, and the number of bytes to allocate for storing history lines is set by thehistlen 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 canbe stored, see the description of the gl_limit_history()
function. If you do not 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.The del_GetLine() function deletes the resources that were
returned by a previous call to new_GetLine(). It always
returns NULL (for example, a deleted object). It does noth-
ing if the gl argument is NULL.The gl_get_line() function can be called any number of times
to read input from the user. The gl argument must have beenpreviously returned by a call to new_GetLine(). The prompt
argument should be a normal null-terminated string, specify-
ing the prompt to present the user with. By default prompts are displayed literally, but if enabled with thegl_prompt_style() function, prompts can contain directives
to do underlining, switch to and from bold fonts, or turn highlighting on and off.SunOS 5.11 Last change: 28 Nov 2007 5
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If you want to specify the initial contents of the line for the user to edit, pass the desired string with thestart_line argument. You can then specify which character of
this line the cursor is initially positioned over by usingthe start_pos argument. This should be -1 if you want the
cursor to follow the last character of the start line. If you do not want to preload the line in this manner, sendstart_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 freed 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 youshould call gl_get_line() again to read the rest of the
line. Note that this behavior makes gl_get_line() similar to
fgets(3C). When stdin is not connected to a terminal,gl_get_line() simply calls fgets().
The Return Status Of gl_get_line()
The gl_get_line() function has two possible return values: a
pointer to the completed input line, or NULL. Additionalinformation about what caused gl_get_line() to return is
available both by inspecting errno and by calling thegl_return_status() function.
The following are the possible enumerated values returned bygl_return_status():
GLR_NEWLINE The last call to gl_get_line() successfully
returned a completed input line.GLR_BLOCKED The gl_get_line() function was in non-
blocking server mode, and returned early to avoid blocking the process while waiting forterminal I/O. The gl_pending_io() function
can be used to see what type of I/O
gl_get_line() was waiting for. See the
gl_io_mode(3TECLA).
GLR_SIGNAL A signal was caught by gl_get_line() that had
an after-signal disposition of GLS_ABORT. See
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gl_trap_signal().
GLR_TIMEOUT The inactivity timer expired while
gl_get_line() was waiting for input, and the
timeout callback function returnedGLTO_ABORT. See gl_inactivity_timeout() for
information about timeouts.GLR_FDABORT An application I/O callback returned
GLFD_ABORT. Ssee gl_watch_fd().
GLR_EOF End of file reached. This can happen when
input is coming from a file or a pipe, instead of the terminal. It also occurs ifthe user invokes the list-or-eof or del-
char-or-list-or-eof actions at the start of a
new line.GLR_ERROR An unexpected error caused gl_get_line() to
abort (consult errno and/orgl_error_message() for details.
When gl_return_status() returns GLR_ERROR and the value of
errno is not sufficient to explain what happened, you canuse the gl_error_message() function to request a description
of the last error that occurred.The return value of gl_error_message() is a pointer to the
message that occurred. If the buff argument is NULL, this will be a pointer to a buffer within gl whose value will probably change on the next call to any function associatedwith gl_get_line(). Otherwise, if a non-null buff argument
is provided, the error message, including a '\0' terminator, will be written within the first n elements of this buffer, and the return value will be a pointer to the first element of this buffer. If the message will not fit in the provided buffer, it will be truncated to fit. Optional Prompt Formatting Whereas by default the prompt string that you specify is displayed literally without any special interpretation ofthe characters within it, the gl_prompt_style() function can
be used to enable optional formatting directives within the prompt.SunOS 5.11 Last change: 28 Nov 2007 7
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The style argument, which specifies the formatting style, can take any of the following values:GL_FORMAT_PROMPT In this style, the formatting direc-
tives described below, when included inprompt strings, are interpreted as fol-
lows:%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 bright-
ness) 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 promptSunOS 5.11 Last change: 28 Nov 2007 8
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string like "%UOK%u$" would display the
prompt "OK$", but with the OK part
underlined. Note that although a pair of charactersthat starts with a % character, but
does not match any of the above direc-
tives is displayed literally, if a new directive is subsequently introduced which does match, the displayed prompt will change, so it is better to alwaysuse %% to display a literal %.
Also note that not all terminals sup-
port all of these text attributes, andthat some substitute a different attri-
bute for missing ones.GL_LITERAL_PROMPT In this style, the prompt string is
printed literally. This is the default style. Alternate Configuration Sources By default users have the option of configuring the behaviorof gl_get_line() with 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 ofkeybindings is needed to emulate a legacy keyboard inter-
face. To cater for such cases, the gl_configure_getline()
function allows the application to control where configura-
tion information is read from.The gl_configure_getline() function 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 calledbefore 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 configurations must be achieved using the configuration sources specified with this function.SunOS 5.11 Last change: 28 Nov 2007 9
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If app_string != NULL, then it is interpreted as a string
containing one or more configuration commands, separatedfrom 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 callgl_configure_getline(gl, "edit-mode vi 0obeep",
"/usr/share/myapp/teclarc", "~/.teclarc");The app_string argument causes the calling application to
start in vi(1) 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, thenfinally reads user-specific configuration commands from an
optional .teclarc file in the user's home directory. Notethat 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 with 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.
Individual key sequences can also be bound and unbound usingthe gl_bind_keyseq() function. The origin argument specifies
the priority of the binding, according to whom it is being established for, and must be one of the following two values.GL_USER_KEY The user requested this key-binding.
GL_APP_KEY This is a default binding set by the applica-
tion.SunOS 5.11 Last change: 28 Nov 2007 10
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When both user and application bindings for a given keysequence have been specified, the user binding takes pre-
cedence. The application's binding is subsequently rein-
stated if the user's binding is later unbound with either another call to this function, or a call togl_configure_getline().
The keyseq argument specifies the key sequence to be bound or unbound, and is expressed in the same way as in a ~/.teclarc configuration file. The action argument must either be a string containing the name of the action to bind the key sequence to, or it must be NULL or "" to unbind the key sequence. 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 with a call to thegl_customize_completion() function.
The data argument provides a way for your application topass 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. Thematch_fn argument specifies the callback function to be
called. The CplMatchFn function type is defined into declare and prototype callback functions. The declaration and responsibilities of callback functions are described in
, as is a CPL_MATCH_FN() macro that you can use depth on the cpl_complete_word(3TECLA) manual page.
The callback function is responsible for looking backwards in the input line 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 passedto it as an argument, by calling the cpl_add_completion()
function. If the callback function wants to provide filename completion in addition to its own specific completions, ithas the option of itself calling the builtin filename com-
pletion callback. This also is documented on thecpl_complete_word(3TECLA) manual page.
If you would like gl_get_line() to return the current input
line when a successful completion is been made, you canSunOS 5.11 Last change: 28 Nov 2007 11
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arrange this when you call cpl_add_completion() by making
the last character of the continuation suffix a newline character. The input line will be updated to display the completion, together with any contiuation suffix up to thenewline character, and gl_get_line() will return this input
line. If your callback function needs to write something to theterminal, it must call gl_normal_io() before doing so. This
will start a new line after the input line that is currentlybeing edited, reinstate normal terminal I/O, and notify
gl_get_line() that the input line will need to be redrawn
when the callback returns. Adding Completion Actions In the previous section the ability to customize thebehavior of the only default completion action, complete-
word, was described. In this section the ability to install additional action functions, so that different types of word completion can be bound to different key sequences, is described. This is achieved by using thegl_completion_action() function.
The data and match_fn arguments are as described on the
cpl_complete_word(3TECLA) manual page, and specify the call-
back function that should be invoked to identify possiblecompletions. The list_only argument determines whether the
action that is being defined should attempt to complete the word as far as possible in the input line before displaying any possible ambiguous completions, or whether it should simply display the list of possible completions without touching the input line. The former option is selected by specifying a value of 0, and the latter by specifying a value of 1. The name argument specifies the name by which configuration files and future invocations of this function should refer to the action. This must either be the name of an existing completion action to be changed, or be a new unused name for a new action. Finally, the keyseq argument specifies the default key sequence to bind the action to. If this is NULL, no new key sequence will be bound to the action. Beware that in order for the user to be able to change the key sequence that is bound to actions that are installed inthis manner, you shouldcall gl_completion_action() to
install a given action for the first time between callingnew_GetLine() and the first call to gl_get_line(). Other-
wise, when the user's configuration file is read on theSunOS 5.11 Last change: 28 Nov 2007 12
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first call to gl_get_line(), the name of the your additional
action will not be known, and any reference to it in the configuration file will generate an error.As discussed for gl_customize_completion(), if your callback
function needs to write anything to the terminal, it mustcall gl_normal_io() before doing so.
Defining Custom ActionsAlthough the built-in key-binding actions are sufficient for
the needs of most applications, occasionally a specialized application may need to define one or more custom actions,bound to application-specific key sequences. For example, a
sales application would benefit from having a key sequence that displayed the part name that corresponded to a part number preceding the cursor. Such a feature is clearlybeyond the scope of the built-in action functions. So for
such special cases, the gl_register_action() function is
provided.The gl_register_action() function lets the application
register an external function, fn, that will thereafter be called whenever either the specified key sequence, keyseq, is entered by the user, or the user enters any other key sequence that the user subsequently binds to the specified action name, name, in their configuration file. The data argument can be a pointer to anything that the application wants to have passed to the action function, fn, whenever that function is invoked. The action function, fn, should be declared using theGL_ACTION_FN() macro, which is defined in
. #define GL_ACTION_FN(fn) GlAfterAction (fn)(GetLine *gl, \
void *data, int count, size_t curpos, \
const char *line) The gl and data arguments are those that were previouslypassed to gl_register_action() when the action function was
registered. The count argument is a numeric argument whichthe user has the option of entering using the digit-argument
action, before invoking the action. If the user does notenter a number, then the count argument is set to 1. Nomi-
nally this argument is interpreted as a repeat count, mean-
ing that the action should be repeated that many times. In practice however, for some actions a repeat count makesSunOS 5.11 Last change: 28 Nov 2007 13
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gl_get_line(3TECLA)
little sense. In such cases, actions can either simply ignore the count argument, or use its value for a different purpose.A copy of the current input line is passed in the read-only
line argument. The current cursor position within thisstring is given by the index contained in the curpos argu-
ment. Note that direct manipulation of the input line andthe cursor position is not permitted because the rules dic-
tated by various modes (such as vi mode versus emacs mode,no-echo mode, and insert mode versus overstrike mode) make
it too complex for an application writer to write a conform-
ing editing action, as well as constrain future changes tothe internals of gl_get_line(). A potential solution to this
dilemma would be to allow the action function to edit the line using the existing editing actions. This is currently under consideration. If the action function wishes to write text to the terminal without this getting mixed up with the displayed text of theinput line, or read from the terminal without having to han-
dle raw terminal I/O, then before doing either of these
operations, it must temporarily suspend line editing by cal-
ling the gl_normal_io() function. This function flushes any
pending output to the terminal, moves the cursor to the start of the line that follows the last terminal line of the input line, then restores the terminal to a state that is suitable for use with the C stdio facilities. The latter includes such things as restoring the normal mapping of \n to \r\n, and, when in server mode, restoring the normalblocking form of terminal I/O. Having called this function, the action function can read from and write to the terminal without the fear of creating a mess. It is not necessary for
the action function to restore the original editing environ-
ment before it returns. This is done automatically bygl_get_line() after the action function returns. The follow-
ing is a simple example of an action function which writes the sentence "Hello world" on a new terminal line after the line being edited. When this function returns, the input line is redrawn on the line that follows the "Hello world" line, and line editing resumes.static GL_ACTION_FN(say_hello_fn)
{if(gl_normal_io(gl)) /* Temporarily suspend editing */
return GLA_ABORT;
printf("Hello world\n");return GLA_CONTINUE;
}SunOS 5.11 Last change: 28 Nov 2007 14
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Action functions must return one of the following values, totell gl_get_line() how to proceed.
GLA_ABORT Cause gl_get_line() to return NULL.
GLA_RETURN Cause gl_get_line() to return the completed
input lineGLA_CONTINUE Resume command-line editing.
Note that the name argument of gl_register_action() speci-
fies the name by which a user can refer to the action intheir configuration file. This allows them to re-bind the
action to an alternate key-seqeunce. In order for this to
work, it is necessary to call gl_register_action() between
calling new_GetLine() and the first call to gl_get_line().
History Files To save the contents of the history buffer before quitting your application and subsequently restore them when you nextstart the application, the gl_save_history() and
gl_load_history() functions are provided.
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, additional information about it, such as its nesting level and when it was entered by the user, 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 prefixesdiffer 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 Bourneshell, you would specify "#" here. Whatever you choose for
the comment character, you must specify the same prefix togl_load_history() that you used when you called
gl_save_history() to write the history file.
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The max_lines argument 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 ListsIf your application uses a single GetLine object for enter-
ing many different types of input lines, you might wantgl_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().
The integer identifier ID can be any number chosen by theapplication, but note that gl_save_history() and
gl_load_history() preserve the association between identif-
iers and historical input lines between program invocations, 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 callinggl_show_history(). This function displays the current con-
tents of the history list to the stdio output stream fp. Ifthe max_lines argument is greater than or equal to zero,
then no more than this number of the most recent lines willbe displayed. If the all_groups argument is non-zero, lines
from all history groups are displayed. Otherwise only 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 arewritten verbatim, interleaved with any of the following for-
mat directives:SunOS 5.11 Last change: 28 Nov 2007 16
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%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 HistoryThe gl_lookup_history() function allows the calling applica-
tion to look up lines in the history list. The id argument indicates which line to look up, where the first line that was entered in the history list afternew_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 thegl_range_of_history() function. 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.SunOS 5.11 Last change: 28 Nov 2007 17
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Beware that the string returned in hline->line is part of
the history buffer, so it must not be modified by thecaller, 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. Manual History Archival By default, whenever a line is entered by the user, it is automatically appended to the history list, just beforegl_get_line() returns the line to the caller. This is con-
venient for the majority of applications, but there are alsoapplications that need finer-grained control over what gets
added to the history list. In such cases, the automatic addition of entered lines to the history list can be turnedoff by calling the gl_automatic_history() function.
If this function is called with its enable argument set to0, gl_get_line() will not automatically archive subsequently
entered lines. Automatic archiving can be reenabled at a later time by calling this function again, with its enableargument set to 1. While automatic history archiving is dis-
abled, the calling application can use thegl_append_history() to append lines to the history list as
needed.The line argument specifies the line to be added to the his-
tory list. This must be a normal '\0 ' terminated string. If this string contains any newline characters, the line that gets archived in the history list will be terminated by the first of these. Otherwise it will be terminated by the '\0 ' terminator. If the line is longer than the maximum inputline length that was specified when new_GetLine() was
called, it will be truncated to the actual gl_get_line()
line length when the line is recalled.If successful, gl_append_history() returns 0. Otherwise it
returns non-zero and sets errno to one of the following
values.EINVAL One of the arguments passed to gl_append_history()
was NULL. ENOMEM The specified line was longer than the allocated size of the history buffer (as specified whennew_GetLine() was called), so it could not be
archived.SunOS 5.11 Last change: 28 Nov 2007 18
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A textual description of the error can optionally beobtained by calling gl_error_message(). Note that after such
an error, the history list remains in a valid state to receive new history lines, so there is little harm in simplyignoring the return status of gl_append_history().
Miscellaneous History Configuration If you wish to change the size of the history buffer thatwas originally specified in the call to new_GetLine(), you
can do so with the gl_resize_history() function.
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 20 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 memoryused in this list, you can call the gl_limit_history() func-
tion.The max_lines should either be a positive number >= 0,
specifying an upper limit on the number of lines in thebuffer, 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 thegl_clear_history() function.
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.SunOS 5.11 Last change: 28 Nov 2007 19
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Setting the enable argument to 0 turns off the historymechanism, 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 withthe gl_history_state() function. 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. 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 linesin 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. On return, the size information is recorded in the variable pointed to by the size argument. Changing TerminalsThe new_GetLine() constructor function assumes that input is
to be read from stdin and output written to stdout. The fol-
lowing function allows you to switch to different input and output streams. The gl argument is the object that was returned bynew_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 interac-
tive terminal input be enabled. Otherwise gl_get_line() will
simply call fgets() to read command input. If both streamsrefer to a terminal, then they must refer to the same termi-
nal, and the type of this terminal must be specified with 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 controlsequences are needed to control various aspects of the ter-
minal. new_GetLine() for example, passes the return value of
getenv("TERM") in this argument. Note that if one or both ofSunOS 5.11 Last change: 28 Nov 2007 20
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input_fp and output_fp do not 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 togl_change_terminal(), you can do this by creating stdio
stream wrappers using the POSIX fdopen(3C) function. External Event HandlingBy default, gl_get_line() does not return until either a
complete input line has been entered by the user, or anerror occurs. In programs that need to watch for I/O from other sources than the terminal, there are two options. o Use the functions described in the
gl_io_mode(3TECLA) manual page to switch
gl_get_line() into non-blocking server mode. In
this mode, gl_get_line() becomes a non-blocking,
incremental line-editing function that can safely
be called from an external event loop. Although this is a very versatile method, it involves takingon some responsibilities that are normally per-
formed behind the scenes by gl_get_line().
o 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 asnetwork sockets or pipes, and have it call func-
tions 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. If this returns
non-zero, then it means that either your arguments are
invalid, or that this facility is not 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.SunOS 5.11 Last change: 28 Nov 2007 21
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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 thanone 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. When this hap-
pens, gl_get_line() returns NULL, and a
following call to gl_return_status() will
return GLR_FDABORT. Note that if the appli-
cation needs errno always to have a mean-
ingful value when gl_get_line() returns
NULL, the callback function should set errno appropriately.GLFD_REFRESH Redraw the input line then continue wait-
ing for input. Return this if your callback wrote to the terminal.GLFD_CONTINUE Continue to wait for input, without redraw-
ing 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, andunblock the signal. Be sure to re-block the signal (if it
was originally blocked) and reinstate the original signal handler, if any, before returning.SunOS 5.11 Last change: 28 Nov 2007 22
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Your callback should not try to read from the terminal, which is left in raw mode as far as input is concerned. You can write to the terminal as usual, since features likeconversion 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, tellgl_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 callgl_watch_fd() with the same fd and event arguments, but with
a callback argument of 0. The data argument is ignored in this case. Setting An Inactivity TimeoutThe gl_inactivity_timeout() function can be used to set or
cancel an inactivity timeout. Inactivity in this case refersboth to keyboard input, and to I/O on any file descriptors
registered by prior and subsequent calls to gl_watch_fd().
The timeout is specified in the form of an integral number of seconds and an integral number of nanoseconds, specified by the sec and nsec arguments, respectively. Subsequently,whenever no activity is seen for this time period, the func-
tion specified by the callback argument is called. The dataargument of gl_inactivity_timeout() is passed to this call-
back function whenever it is invoked, and can thus be usedto pass arbitrary application-specific information to the
callback. The following macro is provided infor applications to use to declare and prototype timeout callback functions. #define GL_TIMEOUT_FN(fn) GlAfterTimeout (fn)(GetLine *gl, void *data)
On returning, the application's callback is expected to return one of the following enumerators to tellgl_get_line() how to procede after the timeout has been han-
dled by the callback.GLTO_ABORT Tell gl_get_line() to abort. When this hap-
pens, gl_get_line() will return NULL, and a
following call to gl_return_status() will
return GLR_TIMEOUT. Note that if the appli-
cation needs errno always to have a mean-
ingful value when gl_get_line() returns
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NULL, the callback function should set errno appropriately.GLTO_REFRESH Redraw the input line, then continue wait-
ing for input. You should return this value if your callback wrote to the terminal.GLTO_CONTINUE In normal blocking-I/O mode, continue to
wait for input, without redrawing theuser's input line. In non-blocking server
I/O mode (see gl_io_mode(3TECLA)),
gl_get_line() acts as though I/O blocked.
This means that gl_get_line() will immedi-
ately return NULL, and a following call togl_return_status() will return GLR_BLOCKED.
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 unblockthe signal. Be sure to re-block the signal (if it was origi-
nally blocked) and reinstate the original signal handler, if any, before returning. Your callback should not 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 featureslike 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, tellgl_get_line() that the input line needs to be redrawn, by
returning the GLTO_REFRESH status code.
Finally, note that although the timeout arguments include a nanosecond component, few computer clocks presently haveresolutions that are finer than a few milliseconds, so ask-
ing for less than a few milliseconds is equivalent to requesting zero seconds on many systems. If this would be a problem, you should base your timeout selection on the actual resolution of the host clock (for example, by callingsysconf(_SC_CLK_TCK)).
SunOS 5.11 Last change: 28 Nov 2007 24
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To turn off timeouts, simply call gl_inactivity_timeout()
with a callback argument of 0. The data argument is ignored in this case. Signal Handling DefaultsBy default, the gl_get_line() function intercepts a number
of signals. This is particularly important for signals that would by default terminate the process, since the terminal needs to be restored to a usable state before this happens. This section describes the signals that are trapped bydefault and how gl_get_line() responds to them. 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 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 theprocess still exists, returns NULL and sets errno as speci-
fied below. SIGINT This signal is generated both by the keyboard interrupt key (usually ^C), and the keyboard break key. The errno value is EINTR. SIGHUP This signal is generated when the controlling terminal exits. The errno value is ENOTTY. SIGPIPE This signal is generated when a program attempts to write to a pipe whose remote end is not being read by any process. This can happen for exampleif you have called gl_change_terminal() to
redirect output to a pipe hidden under a pseudo terminal. The errno value is EPIPE. SIGQUIT This signal is generated by the keyboard quit key (usually ^\fR). The errno value is EINTR. SIGABRT This signal is generated by the standard C, abortfunction. By default it both terminates the pro-
cess and generates a core dump. The errno value is EINTR. SIGTERM This is the default signal that the UNIX kill command sends to processes. The errno value isSunOS 5.11 Last change: 28 Nov 2007 25
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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 does not override the default handler by supplying its own signal handler, receipt of the corresponding signal will terminate theapplication 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 thegl_last_signal() function. This returns the numeric code
(for example, SIGINT) of the last signal that was receivedduring 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 toaccomodate the new size, then returns to waiting for key-
board input from the user. Unlike other signals, this signal is not resent to the application.Finally, the following signals cause gl_get_line() to first
restore the terminal and signal environment to that whichprevailed before gl_get_line() was called, then resend the
signal to the application. If the process still exists afterthe 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 pro-
cess is resumed.SIGPOLL On SVR4 systems, this signal notifies the pro-
cess of an asynchronous I/O event. Note that under 4.3+BSD, SIGIO and SIGPOLL are the same. On other systems, SIGIO is ignored by default,
so gl_get_line() does not trap it by default.
SIGPWR This signal is generated when a power failure occurs (presumably when the system is on aSunOS 5.11 Last change: 28 Nov 2007 26
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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 setitimer(2). SIGXCPU This signal is generated when a process exceeds its soft CPU time limit. SIGXFSZ This signal is generated when a process exceedsits soft file-size 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 or SIGPOLL, which by definition cannotbe caught, or any of the hardware generated exception sig-
nals, such as SIGSEGV, SIGBUS, and SIGFPE, are received andunhandled while gl_get_line() has the terminal in raw mode,
the program will be terminated without the terminal havingSunOS 5.11 Last change: 28 Nov 2007 27
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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 HandlingThe 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 howgl_get_line() should respond to a given signal.
If you do not need gl_get_line() to do anything in response
to a signal that it normally traps, you can tell togl_get_line() to ignore that signal by calling
gl_ignore_signal().
The signo argument is the number of the signal (for example,SIGINT) that you want to have ignored. If the specified sig-
nal is not currently one of those being trapped, this func-
tion 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. The signo argument is the number of the signal that you want to have trapped. The flags argument is a set of flags that determine the environment in which the application's signalhandler is invoked. The after argument tells gl_get_line()
what to do after the application's signal handler returns.The 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.SunOS 5.11 Last change: 28 Nov 2007 28
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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 (see sigprocmask(2)),gl_get_line() does not trap that signal.
This flag tells gl_get_line() to trap
the signal and unblock it for the dura-
tion 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 have not overridden it, never eitherwrites to the terminal, nor suspends or terminates the cal-
ling program, then you can safely set the flags argument to 0. o The cursor does not get left in the middle of the input line. o So that the user can type in input and have it echoed. o So that you do not need to end each output line with \r\n, instead of just \n.SunOS 5.11 Last change: 28 Nov 2007 29
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The GL_RESTORE_ENV combination is the same as
GL_SUSPEND_INPUT, except that it does not move the cursor.
If your signal handler does not read or write anything to the terminal, the user will not see any visible indication that a signal was caught. This can be useful if you have asignal handler that only occasionally writes to the termi-
nal, 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 does not 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 abort. When this hap-
pens, gl_get_line() returns NULL, and a fol-
lowing call to gl_return_status() will
return GLR_SIGNAL. Note that if the applica-
tion needs errno always to have a meaningfulvalue when gl_get_line() returns NULL, the
callback function should set errno appropri-
ately.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 theGL_RETURN option, in case you want 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 aSunOS 5.11 Last change: 28 Nov 2007 30
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signal. Reliable Signal Handling Signal handling is suprisingly hard to do reliably withoutrace conditions. In gl_get_line() a lot of care has been
taken to allow applications to perform reliable signal han-
dling around gl_get_line(). This section explains how to
make use of this.As an example of the problems that can arise if the applica-
tion is not written correctly, imagine that one's applica-
tion has a SIGINT signal handler that sets a global flag. Now suppose that the application tests this flag just beforeinvoking gl_get_line(). If a SIGINT signal happens to be
received in the small window of time between the statement that tests the value of this flag, and the statement thatcalls gl_get_line(), then gl_get_line() will not see the
signal, and will not be interrupted. As a result, the appli-
cation will not be able to respond to the signal until the user gets around to finishing entering the input line andgl_get_line() returns. Depending on the application, this
might or might not be a disaster, but at the very least it would puzzle the user. The way to avoid such problems is to do the following.1. If needed, use the gl_trap_signal() function to
configure gl_get_line() to abort when important
signals are caught.2. Configure gl_get_line() such that if any of the
signals that it catches are blocked whengl_get_line() is called, they will be unblocked
automatically during times when gl_get_line() is
waiting for I/O. This can be done either on a per
signal basis, by calling the gl_trap_signal() func-
tion, and specifying the GLS_UNBLOCK attribute of
the signal, or globally by calling thegl_catch_blocked() function. This function simply
adds the GLS_UNBLOCK attribute to all of the sig-
nals that it is currently configured to trap.3. Just before calling gl_get_line(), block delivery
of all of the signals that gl_get_line() is config-
ured to trap. This can be done using the POSIX sig-
procmask function in conjunction with thegl_list_signals() function. This function returns
the set of signals that it is currently configured to catch in the set argument, which is in the formSunOS 5.11 Last change: 28 Nov 2007 31
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required by sigprocmask(2). 4. In the example, one would now test the global flag that the signal handler sets, knowing that there is now no danger of this flag being set again untilgl_get_line() unblocks its signals while performing
I/O.
5. Eventually gl_get_line() returns, either because a
signal was caught, an error occurred, or the user finished entering their input line. 6. Now one would check the global signal flag again, and if it is set, respond to it, and zero the flag. 7. Use sigprocmask() to unblock the signals that were blocked in step 3.The same technique can be used around certain POSIX signal-
aware functions, such as sigsetjmp(3C) and sigsuspend(2), and in particular, the former of these two functions can beused in conjunction with siglongjmp(3C) to implement race-
condition free signal handling around other long-running
system calls. The gl_get_line() function manages to reliably
trap signals around calls to functions like read(2) and select(3C) without race conditions.The gl_get_line() function first uses the POSIX sigproc-
mask() function to block the delivery of all of the signals that it is currently configured to catch. This is redundant if the application has already blocked them, but it does no harm. It undoes this step just before returning.Whenever gl_get_line() needs to call read or select to wait
for input from the user, it first calls the POSIX sig-
setjmp() function, being sure to specify a non-zero value
for its savemask argument.If sigsetjmp() returns zero, gl_get_line() then does the
following. 1. It uses the POSIX sigaction(2) function to register a temporary signal handler to all of the signals that it is configured to catch. This signal handler does two things. a. It records the number of the signal that wasSunOS 5.11 Last change: 28 Nov 2007 32
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received in a file-scope variable.
b. It then calls the POSIX siglongjmp() function using the buffer that was passed to sigsetjmp()for its first argument and a non-zero value for
its second argument.When this signal handler is registered, the sa_mask
member of the struct sigaction act argument of the callto sigaction() is configured to contain all of the sig-
nals that gl_get_line() is catching. This ensures that
only one signal will be caught at once by our signal handler, which in turn ensures that multiple instances of our signal handler do not tread on each other's toes. 2. Now that the signal handler has been set up,gl_get_line() unblocks all of the signals that it
is configured to catch. 3. It then calls the read() or select() function to wait for keyboard input. 4. If this function returns (that is, no signal isreceived), gl_get_line() blocks delivery of the
signals of interest again. 5. It then reinstates the signal handlers that were displaced by the one that was just installed.Alternatively, if sigsetjmp() returns non-zero, this means
that one of the signals being trapped was caught while theabove steps were executing. When this happens, gl_get_line()
does the following.First, note that when a call to siglongjmp() causes sig-
setjmp() to return, provided that the savemask argument ofsigsetjmp() was non-zero, the signal process mask is
restored to how it was when sigsetjmp() was called. This is the important difference between sigsetjmp() and the older problematic setjmp(3C), and is the essential ingredient that makes it possible to avoid signal handling race conditions. Because of this we are guaranteed that all of the signals that we blocked before calling sigsetjmp() are blocked again as soon as any signal is caught. The following statements, which are then executed, are thus guaranteed to be executed without any further signals being caught.1. If so instructed by the gl_get_line() configuration
attributes of the signal that was caught,gl_get_line() restores the terminal attributes to
SunOS 5.11 Last change: 28 Nov 2007 33
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the state that they had when gl_get_line() was
called. This is particularly important for signalsthat suspend or terminate the process, since other-
wise the terminal would be left in an unusable state. 2. It then reinstates the application's signal handlers.3. Then it uses the C standard-library raise(3C) func-
tion to re-send the application the signal that was
caught. 4. Next it unblocks delivery of the signal that we just sent. This results in the signal that was just sent by raise() being caught by the application's original signal handler, which can now handle it as it sees fit. 5. If the signal handler returns (that is, it does notterminate the process), gl_get_line() blocks
delivery of the above signal again. 6. It then undoes any actions performed in the first of the above steps and redisplays the line, if the signal configuration calls for this.7. gl_get_line() then either resumes trying to read a
character, or aborts, depending on the configura-
tion of the signal that was caught. What the above steps do in essence is to take asynchronously delivered signals and handle them synchronously, one at atime, at a point in the code where gl_get_line() has com-
plete control over its environment. 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 everytime that gl_get_line() is called and whenever a SIGWINCH
signal is received. On the few systems where this mechanism is not available, atstartup new_GetLine() first looks for the LINES and COLUMNS
environment variables. If these are not found, or they con-
tain unusable values, then if a terminal information data-
base like terminfo or termcap is available, the default sizeSunOS 5.11 Last change: 28 Nov 2007 34
Interactive Command-line Input Library Functions
gl_get_line(3TECLA)
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. Even on systems that do support ioctl(TIOCGWINSZ), if the terminal is on the other end of a serial line, the terminal driver generally has no way of detecting when a resize occurs or of querying what the current size is. In such cases no SIGWINCH is sent to the process, and the dimensions returned by ioctl(TIOCGWINSZ) are not correct. The only way to handle such instances is to provide a way for the user to enter a command that tells the remote system what the newsize is. This command would then call the gl_set_term_size()
function to tell gl_get_line() about the change in size.
The ncolumn and nline arguments are used to specify the new dimensions of the terminal, and must not be less than 1. On systems that do support ioctl(TIOCGWINSZ), this function first calls ioctl(TIOCSWINSZ) to tell the terminal driverabout the change in size. In non-blocking server-I/O mode,
if a line is currently being input, the input line is then redrawn to accomodate the changed size. Finally the newvalues are recorded in gl for future use by gl_get_line().
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 is not available. Beware that the terminal size will not be available if reading from a pipe or a file, so the default values can be importanteven on systems that do support ways of finding out the ter-
minal size.This function first updates gl_get_line()'s fallback termi-
nal dimensions, then records its findings in the return value.The def_ncolumn and def_nline arguments specify the default
number of terminal columns and lines to use if the terminalsize cannot be determined by ioctl(TIOCGWINSZ) or environ-
ment variables. 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 terminalSunOS 5.11 Last change: 28 Nov 2007 35
Interactive Command-line Input Library Functions
gl_get_line(3TECLA)
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 thatis subsequently entered in calls to gl_get_line().
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 subsequentinput lines will be displayed as they are entered, and pro-
vided that history has not been turned off with a call togl_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 tonon-destructively query the current setting through 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. Single Character QueriesUsing gl_get_line() to query the user for a single character
reply, is inconvenient for the user, since they must hit the enter or return key before the character that they typed isreturned to the program. Thus the gl_query_char() function
has been provided for single character queries like this. This function displays the specified prompt at the start of a new line, and waits for the user to type a character. Whenthe user types a character, gl_query_char() displays it to
the right of the prompt, starts a newline, then returns the character to the calling program. The return value of the function is the character that was typed. If the read had to be aborted for some reason, EOF is returned instead. In thelatter case, the application can call the previously docu-
mented gl_return_status(), to find out what went wrong. This
could, for example, have been the reception of a signal, or the optional inactivity timer going off. If the user simply hits enter, the value of the defchar argument is substituted. This means that when the user hits either newline or return, the character specified in defchar, is displayed after the prompt, as though the userSunOS 5.11 Last change: 28 Nov 2007 36
Interactive Command-line Input Library Functions
gl_get_line(3TECLA)
had typed it, as well as being returned to the calling application. If such a replacement is not important, simply pass '\n' as the value of defchar. If the entered character is an unprintable character, it isdisplayed symbolically. For example, control-A is displayed
as ^A, and characters beyond 127 are displayed in octal, preceded by a backslash.As with gl_get_line(), echoing of the entered character can
be disabled using the gl_echo_mode() function.
If the calling process is suspended while waiting for the user to type their response, the cursor is moved to the line following the prompt line, then when the process resumes,the prompt is redisplayed, and gl_query_char() resumes wait-
ing for the user to type a character.Note that in non-blocking server mode, if an incomplete
input line is in the process of being read whengl_query_char() is called, the partial input line is dis-
carded, and erased from the terminal, before the new promptis displayed. The next call to gl_get_line() will thus start
editing a new line. Reading Raw CharactersWhereas the gl_query_char() function visibly prompts the
user for a character, and displays what they typed, thegl_read_char() function reads a signal character from the
user, without writing anything to the terminal, or perturb-
ing any incompletely entered input line. This means that itcan be called not only from between calls to gl_get_line(),
but also from callback functions that the application hasregistered to be called by gl_get_line().
On success, the return value of gl_read_char() is the char-
acter that was read. On failure, EOF is returned, and thegl_return_status() function can be called to find out what
went wrong. Possibilities include the optional inactivity timer going off, the receipt of a signal that is configuredto abort gl_get_line(), or terminal I/O blocking, when in
non-blocking server-I/O mode.
Beware that certain keyboard keys, such as function keys, and cursor keys, usually generate at least three charactersSunOS 5.11 Last change: 28 Nov 2007 37
Interactive Command-line Input Library Functions
gl_get_line(3TECLA)
each, so a single call to gl_read_char() will not be enough
to identify such keystrokes. Clearing The Terminal The calling program can clear the terminal by callinggl_erase_terminal(). In non-blocking server-I/O mode, this
function also arranges for the current input line to beredrawn from scratch when gl_get_line() is next called.
Displaying Text DynamicallyBetween calls to gl_get_line(), the gl_display_text() func-
tion provides a convenient way to display paragraphs oftext, left-justified and split over one or more terminal
lines according to the constraints of the current width of the terminal. Examples of the use of this function may be found in the demo programs, where it is used to display introductions. In those examples the advanced use of optional prefixes, suffixes and filled lines to draw a box around the text is also illustrated. If gl is not currently connected to a terminal, for exampleif the output of a program that uses gl_get_line() is being
piped to another program or redirected to a file, then thevalue of the def_width parameter is used as the terminal
width. The indentation argument specifies the number of charactersto use to indent each line of ouput. The fill_char argument
specifies the character that will be used to perform this indentation. The prefix argument can be either NULL or a string to place at the beginning of each new line (after any indentation). Similarly, the suffix argument can be either NULL or a string to place at the end of each line. The suffix is placed flush against the right edge of the terminal, and any space between its first character and the last word on thatline is filled with the character specified by the fill_char
argument. Normally the fill-character is a space.
The start argument tells gl_display_text() how many charac-
ters have already been written to the current terminal line, and thus tells it the starting column index of the cursor.Since the return value of gl_display_text() is the ending
column index of the cursor, by passing the return value of one call to the start argument of the next call, a paragraph that is broken between more than one string can be composedSunOS 5.11 Last change: 28 Nov 2007 38
Interactive Command-line Input Library Functions
gl_get_line(3TECLA)
by calling gl_display_text() for each successive portion of
the paragraph. Note that literal newline characters are necessary at the end of each paragraph to force a new line to be started.On error, gl_display_text() returns -1.
Callback Function FacilitiesUnless otherwise stated, callback functions such as tab com-
pletion 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. Except in non-blocking server mode, it has
no effect if used between calls to gl_get_line(). In non-
blocking server mode, when used between two calls togl_get_line() that are operating on the same input line, the
current input line will be re-drawn with the new prompt on
the following call to gl_get_line().
International Character SetsSince libtecla(3LIB) 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 theenvironment 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 setlocale(3C), then the default C locale is used, which isUS 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. Further documentation on how the user can make use of this to enter international characters canSunOS 5.11 Last change: 28 Nov 2007 39
Interactive Command-line Input Library Functions
gl_get_line(3TECLA)
be found in the tecla(5) man page. Thread Safety Unfortunately neither terminfo nor termcap were designed to be reentrant, so you cannot safely use the functions of the getline module in multiple threads (you can use the separatefile-expansion and word-completion modules in multiple
threads, see the corresponding man pages for details). How-
ever due to the use of POSIX reentrant functions for looking up home directories, it is safe to use this module from asingle thread of a multi-threaded program, provided that
your other threads do not use any termcap or terminfo func-
tions.ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Interface Stability | Committed ||_____________________________|_____________________________|
| MT-Level | MT-Safe |
|_____________________________|_____________________________|
SEE ALSO
cpl_complete_word(3TECLA), ef_expand_file(3TECLA),
gl_io_mode(3TECLA), libtecla(3LIB), pca_lookup_file(3TECLA),
attributes(5), tecla(5)SunOS 5.11 Last change: 28 Nov 2007 40
Interactive Command-line Input Library Functions
gl_get_line(3TECLA)
SunOS 5.11 Last change: 28 Nov 2007 41