wordexp
NAME
wordexp, wordfree - perform word expansion like a posix-shell
SYNOPSIS
#include <wordexp.h>
I int wordexp(const char * s , wordexp_t * p , int flags );
I void wordfree(wordexp_t * p );
DESCRIPTION
The function
R wordexp ()
performs a shell-like expansion of the string
s
and returns the result in the structure pointed to by
R p .
The data type
wordexp_t
is a structure that at least has the fields
R we_wordc ,
R we_wordv ,
and
R we_offs .
The field
we_wordc
is a
size_t
that gives the number of words in the expansion of
R 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
R flags ,
see below) used to indicate the number of initial elements in the
we_wordv
array that should be filled with NULLs.
The function
R 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.
Example
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);
}
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
R we_wordv .
(These are not counted in the returned
R we_wordc .)
WRDE_NOCMD
Don't do command substitution.
WRDE_REUSE
The parameter
p
resulted from a previous call to
R wordexp (),
and
R wordfree ()
was not called.
Reuse the allocated storage.
WRDE_SHOWERR
Normally during command substitution
stderr
is redirected to
R /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.
RETURN VALUE
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.
CONFORMING TO
POSIX.1-2001
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