GNU/Linux man pages
Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
GNU/Linux |
CentOS 5.4 |
|
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wordexp(3) |
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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);
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);
return 0;
}
The string
argument
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
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 output
array
The array we_wordv contains the words found, followed
by a NULL.
The flags
argument
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.
POSIX.1-2001
fnmatch(3), glob(3)
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wordexp(3) | |