wordexp, wordfree — perform word expansion like a posix-shell
#include <wordexp.h>
int
wordexp( |
const char *s, |
| wordexp_t *p, | |
int flags); |
void
wordfree( |
wordexp_t *p); |
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Note | ||
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The function wordexp()
performs a shell-like expansion of the string s and returns the result in the
structure pointed to by p. The data type wordexp_t is a structure that at least has the
fields we_wordc, we_wordv, and we_offs. The field we_wordc is a size_t that gives the number of words in the
expansion of s. The
field we_wordv is a char ** that points to the array
of words found. The field we_offs of type size_t is sometimes (depending on flags, see below) used to
indicate the number of initial elements in the we_wordv array that should be filled with
NULLs.
The function wordfree()
frees the allocated memory again. More precisely, it does not
free its argument, but it frees the array we_wordv and the strings that points to.
Since the expansion is the same as the expansion by the
shell (see sh(1)) of the parameters to a
command, the string s must not contain characters
that would be illegal in shell command parameters. In
particular, there must not be any unescaped newline or |,
&, ;, <, >, (, ), {, } characters outside a
command substitution or parameter substitution context.
If the argument s contains a word that starts
with an unquoted comment character #, then it is
unspecified whether that word and all following words are
ignored, or the # is treated as a non-comment
character.
The expansion done consists of the following stages: tilde expansion (replacing ~user by user's home directory), variable substitution (replacing $FOO by the value of the environment variable FOO), command substitution (replacing $(command) or `command` by the output of command), arithmetic expansion, field splitting, wildcard expansion, quote removal.
The result of expansion of special parameters ($@, $*, $#, $?, $−, $$, $!, $0) is unspecified.
Field splitting is done using the environment variable $IFS. If it is not set, the field separators are space, tab and newline.
The flag
argument is a bitwise inclusive OR of the following
values:
WRDE_APPENDAppend the words found to the array resulting from a previous call.
WRDE_DOOFFSInsert we_offs
initial NULLs in the array we_wordv. (These are not counted in
the returned we_wordc.)
WRDE_NOCMDDon't do command substitution.
WRDE_REUSEThe argument p resulted from a
previous call to wordexp(), and wordfree() was not called. Reuse
the allocated storage.
WRDE_SHOWERRNormally during command substitution stderr is redirected to /dev/null. This flag specifies that
stderr is not to be
redirected.
WRDE_UNDEFConsider it an error if an undefined shell variable is expanded.
In case of success 0 is returned. In case of error one of the following five values is returned.
WRDE_BADCHARIllegal occurrence of newline or one of |, &, ;, <, >, (, ), {, }.
WRDE_BADVALAn undefined shell variable was referenced, and the
WRDE_UNDEF flag told us
to consider this an error.
WRDE_CMDSUBCommand substitution occurred, and the WRDE_NOCMD flag told us to consider
this an error.
WRDE_NOSPACEOut of memory.
WRDE_SYNTAXShell syntax error, such as unbalanced parentheses or unmatched quotes.
The output of the following example program is approximately that of "ls [a-c]*.c".
#include <stdio.h>
#include <stdlib.h>
#include <wordexp.h>
int
main(int argc, char **argv)
{
wordexp_t p;
char **w;
int i;
wordexp("[a−c]*.c", &p, 0);
w = p.we_wordv;
for (i = 0; i < p.we_wordc; i++)
printf("%s\n", w[i]);
wordfree(&p);
exit(EXIT_SUCCESS);
}
This page is part of release 3.72 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
http://www.kernel.org/doc/man−pages/.
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Copyright (c) 2003 Andries Brouwer (aebcwi.nl) %%%LICENSE_START(GPLv2+_DOC_FULL) This is free documentation; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU General Public License's references to "object code" and "executables" are to be interpreted as the output of any document formatting or typesetting system, including intermediate and printed output. This manual is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this manual; if not, see <http://www.gnu.org/licenses/>. %%%LICENSE_END |