illumos: manual page: cpl_complete

CPL_COMPLETE_WORD(3TECLA) Interactive Command-line Input Library Functions

NAME

cpl_complete_word, cfc_file_start, cfc_literal_escapes, cfc_set_check_fn,
cpl_add_completion, cpl_file_completions, cpl_last_error,
cpl_list_completions, cpl_recall_matches, cpl_record_error,
del_CplFileConf, cpl_check_exe, del_WordCompletion, new_CplFileConf,
new_WordCompletion - look up possible completions for a word

SYNOPSIS

cc [ flag... ] file... -ltecla [ library... ]
#include <stdio.h>
#include <libtecla.h>

WordCompletion *new_WordCompletion(void);

WordCompletion *del_WordCompletion(WordCompletion *cpl);

CPL_MATCH_FN(cpl_file_completions);

CplFileConf *new_CplFileConf(void);

void cfc_file_start((CplFileConf *cfc, int start_index);

void cfc_literal_escapes(CplFileConf *cfc, int literal);

void cfc_set_check_fn(CplFileConf *cfc, CplCheckFn *chk_fn,
void *chk_data);

CPL_CHECK_FN(cpl_check_exe);

CplFileConf *del_CplFileConf(CplFileConf *cfc);

CplMatches *cpl_complete_word(WordCompletion *cpl, const char *line,
int word_end, void *data, CplMatchFn *match_fn);

CplMatches *cpl_recall_matches(WordCompletion *cpl);

int cpl_list_completions(CplMatches *result, FILE *fp, int term_width);

int cpl_add_completion(WordCompletion *cpl, const char *line,
int word_start, int word_end, const char *suffix,
const char *type_suffix, const char *cont_suffix);

void cpl_record_error(WordCompletion *cpl, const char *errmsg);

const char *cpl_last_error(WordCompletion *cpl);

DESCRIPTION

The cpl_complete_word() function is part of the libtecla(3LIB) library.
It is usually called behind the scenes by gl_get_line(3TECLA), but can
also be called separately.

Given an input line containing an incomplete word to be completed, it
calls a user-provided callback function (or the provided file-completion
callback function) to look up all possible completion suffixes for that
word. The callback function is expected to look backward in the line,
starting from the specified cursor position, to find the start of the
word to be completed, then to look up all possible completions of that
word and record them, one at a time, by calling cpl_add_completion().

The new_WordCompletion() function creates the resources used by the
cpl_complete_word() function. In particular, it maintains the memory that
is used to return the results of calling cpl_complete_word().

The del_WordCompletion() function deletes the resources that were
returned by a previous call to new_WordCompletion(). It always returns
NULL (that is, a deleted object). It takes no action if the cpl argument
is NULL.

The callback functions that look up possible completions should be
defined with the CPL_MATCH_FN() macro, which is defined in <libtecla.h>.
Functions of this type are called by cpl_complete_word(), and all of the
arguments of the callback are those that were passed to said function. In
particular, the line argument contains the input line containing the word
to be completed, and word_end is the index of the character that follows
the last character of the incomplete word within this string. The
callback is expected to look backwards from word_end for the start of the
incomplete word. What constitutes the start of a word clearly depends on
the application, so it makes sense for the callback to take on this
responsibility. For example, the builtin filename completion function
looks backwards until it encounters an unescaped space or the start of
the line. Having found the start of the word, the callback should then
lookup all possible completions of this word, and record each completion
with separate calls to cpl_add_completion(). If the callback needs access
to an application-specific symbol table, it can pass it and any other
data that it needs using the data argument. This removes any need for
global variables.

The callback function should return 0 if no errors occur. On failure it
should return 1 and register a terse description of the error by calling
cpl_record_error().

The last error message recorded by calling cpl_record_error() can
subsequently be queried by calling cpl_last_error().

The cpl_add_completion() function is called zero or more times by the
completion callback function to record each possible completion in the
specified WordCompletion object. These completions are subsequently
returned by cpl_complete_word(). The cpl, line, and word_end arguments
should be those that were passed to the callback function. The word_start
argument should be the index within the input line string of the start of
the word that is being completed. This should equal word_end if a zero-
length string is being completed. The suffix argument is the string that
would have to be appended to the incomplete word to complete it. If this
needs any quoting (for example, the addition of backslashes before
special characters) to be valid within the displayed input line, this
should be included. A copy of the suffix string is allocated internally,
so there is no need to maintain your copy of the string after
cpl_add_completion() returns.

In the array of possible completions that the cpl_complete_word()
function returns, the suffix recorded by cpl_add_completion() is listed
along with the concatenation of this suffix with the word that lies
between word_start and word_end in the input line.

The type_suffix argument specifies an optional string to be appended to
the completion if it is displayed as part of a list of completions by
cpl_list_completions. The intention is that this indicates to the user
the type of each completion. For example, the file completion function
places a directory separator after completions that are directories, to
indicate their nature to the user. Similarly, if the completion were a
function, you could indicate this to the user by setting type_suffix to
"()". Note that the type_suffix string is not copied, so if the argument
is not a literal string between speech marks, be sure that the string
remains valid for at least as long as the results of cpl_complete_word()
are needed.

The cont_suffix argument is a continuation suffix to append to the
completed word in the input line if this is the only completion. This is
something that is not part of the completion itself, but that gives the
user an indication about how they might continue to extend the token. For
example, the file-completion callback function adds a directory separator
if the completed word is a directory. If the completed word were a
function name, you could similarly aid the user by arranging for an open
parenthesis to be appended.

The cpl_complete_word() function is normally called behind the scenes by
gl_get_line(3TECLA), but can also be called separately if you separately
allocate a WordCompletion object. It performs word completion, as
described at the beginning of this section. Its first argument is a
resource object previously returned by new_WordCompletion(). The line
argument is the input line string, containing the word to be completed.
The word_end argument contains the index of the character in the input
line, that just follows the last character of the word to be completed.
When called by gl_get_line(), this is the character over which the user
pressed TAB. The match_fn argument is the function pointer of the
callback function which will lookup possible completions of the word, as
described above, and the data argument provides a way for the application
to pass arbitrary data to the callback function.

If no errors occur, the cpl_complete_word() function returns a pointer to
a CplMatches container, as defined below. This container is allocated as
part of the cpl object that was passed to cpl_complete_word(), and will
thus change on each call which uses the same cpl argument.

typedef struct {
char *completion; /* A matching completion */
/* string */
char *suffix; /* The part of the */
/* completion string which */
/* would have to be */
/* appended to complete the */
/* original word. */
const char *type_suffix; /* A suffix to be added when */
/* listing completions, to */
/* indicate the type of the */
/* completion. */
} CplMatch;

typedef struct {
char *suffix; /* The common initial part */
/* of all of the completion */
/* suffixes. */
const char *cont_suffix; /* Optional continuation */
/* string to be appended to */
/* the sole completion when */
/* nmatch==1. */
CplMatch *matches; /* The array of possible */
/* completion strings, */
/* sorted into lexical */
/* order. */
int nmatch; /* The number of elements in */
/* the above matches[] */
/* array. */
} CplMatches;

If an error occurs during completion, cpl_complete_word() returns NULL. A
description of the error can be acquired by calling the cpl_last_error()
function.

The cpl_last_error() function returns a terse description of the error
which occurred on the last call to cpl_complete_word() or
cpl_add_completion().

As a convenience, the return value of the last call to
cpl_complete_word() can be recalled at a later time by calling
cpl_recall_matches(). If cpl_complete_word() returned NULL, so will
cpl_recall_matches().

When the cpl_complete_word() function returns multiple possible
completions, the cpl_list_completions() function can be called upon to
list them, suitably arranged across the available width of the terminal.
It arranges for the displayed columns of completions to all have the same
width, set by the longest completion. It also appends the type_suffix
strings that were recorded with each completion, thus indicating their
types to the user.

Builtin Filename completion Callback

By default the gl_get_line() function passes the
CPL_MATCH_FN(cps_file_completions) completion callback function to
cpl_complete_word(). This function can also be used separately, either by
sending it to cpl_complete_word(), or by calling it directly from your
own completion callback function.

#define CPL_MATCH_FN(fn) int (fn)(WordCompletion *cpl, \
void *data, const char *line, \
int word_end)

typedef CPL_MATCH_FN(CplMatchFn);

CPL_MATCH_FN(cpl_file_completions);

Certain aspects of the behavior of this callback can be changed via its
data argument. If you are happy with its default behavior you can pass
NULL in this argument. Otherwise it should be a pointer to a CplFileConf
object, previously allocated by calling new_CplFileConf().

CplFileConf objects encapsulate the configuration parameters of
cpl_file_completions(). These parameters, which start out with default
values, can be changed by calling the accessor functions described below.

By default, the cpl_file_completions() callback function searches
backwards for the start of the filename being completed, looking for the
first unescaped space or the start of the input line. If you wish to
specify a different location, call cfc_file_start() with the index at
which the filename starts in the input line. Passing start_index=-1
reenables the default behavior.

By default, when cpl_file_completions() looks at a filename in the input
line, each lone backslash in the input line is interpreted as being a
special character which removes any special significance of the character
which follows it, such as a space which should be taken as part of the
filename rather than delimiting the start of the filename. These
backslashes are thus ignored while looking for completions, and
subsequently added before spaces, tabs and literal backslashes in the
list of completions. To have unescaped backslashes treated as normal
characters, call cfc_literal_escapes() with a non-zero value in its
literal argument.

By default, cpl_file_completions() reports all files whose names start
with the prefix that is being completed. If you only want a selected
subset of these files to be reported in the list of completions, you can
arrange this by providing a callback function which takes the full
pathname of a file, and returns 0 if the file should be ignored, or 1 if
the file should be included in the list of completions. To register such
a function for use by cpl_file_completions(), call cfc_set_check_fn(),
and pass it a pointer to the function, together with a pointer to any
data that you would like passed to this callback whenever it is called.
Your callback can make its decisions based on any property of the file,
such as the filename itself, whether the file is readable, writable or
executable, or even based on what the file contains.

#define CPL_CHECK_FN(fn) int (fn)(void *data, \
const char *pathname)

typedef CPL_CHECK_FN(CplCheckFn);

void cfc_set_check_fn(CplFileConf *cfc, CplCheckFn *chk_fn, \
void *chk_data);

The cpl_check_exe() function is a provided callback of the above type,
for use with cpl_file_completions(). It returns non-zero if the filename
that it is given represents a normal file that the user has permission to
execute. You could use this to have cpl_file_completions() only list
completions of executable files.

When you have finished with a CplFileConf variable, you can pass it to
the del_CplFileConf() destructor function to reclaim its memory.

Thread Safety

It is safe to use the facilities of this module in multiple threads,
provided that each thread uses a separately allocated WordCompletion
object. In other words, if two threads want to do word completion, they
should each call new_WordCompletion() to allocate their own completion
objects.