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.
First a small example. The output is approximately that of "ls [a-c]*.c".
#include <stdio.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); }
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 non-escaped 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_APPEND
Append the words found to the array resulting from a previous call.
WRDE_DOOFFS
Insert we_offs
initial NULLs
in the array we_wordv
. (These are
not counted in the returned we_wordc
.)
WRDE_NOCMD
Don't do command substitution.
WRDE_REUSE
The parameter p
resulted from a
previous call to wordexp
(), and wordfree
() was not called. Reuse
the allocated storage.
WRDE_SHOWERR
Normally during command substitution stderr
is redirected to /dev/null
. This flag specifies that
stderr
is not to be
redirected.
WRDE_UNDEF
Consider 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_BADCHAR
Illegal occurrence of newline or one of |, &, ;, <, >, (, ), {, }.
WRDE_BADVAL
An undefined shell variable was referenced, and the WRDE_UNDEF flag told us to consider this an error.
WRDE_CMDSUB
Command substitution occurred, and the WRDE_NOCMD flag told us to consider this an error.
WRDE_NOSPACE
Out of memory.
WRDE_SYNTAX
Shell syntax error, such as unbalanced parentheses or unmatched quotes.
Copyright (c) 2003 Andries Brouwer (aeb@cwi.nl) 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, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA. |