WORDEXP
Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
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NAME
wordexp, wordfree - perform word expansion like a posix-shell
SYNOPSIS
#include <wordexp.h>
int wordexp(const char *s, wordexp_t *p, int flags);
void wordfree(wordexp_t *p);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
wordexp(),
wordfree():
_XOPEN_SOURCE
DESCRIPTION
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.
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 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
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 argument
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.
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 requested, but 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.
VERSIONS
wordexp()
and
wordfree()
are provided in glibc since version 2.1.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
wordexp()
| Thread safety |
MT-Unsafe race:utent const:env
env sig:ALRM timer locale
|
|
wordfree()
| Thread safety | MT-Safe
|
In the above table,
utent
in
race:utent
signifies that if any of the functions
setutent(3),
getutent(3),
or
endutent(3)
are used in parallel in different threads of a program,
then data races could occur.
wordexp()
calls those functions,
so we use race:utent to remind users.
CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
EXAMPLE
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);
}
SEE ALSO
fnmatch(3),
glob(3)
COLOPHON
This page is part of release 4.13 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
https://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- The string argument
-
- The expansion
-
- The output array
-
- The flags argument
-
- RETURN VALUE
-
- VERSIONS
-
- ATTRIBUTES
-
- CONFORMING TO
-
- EXAMPLE
-
- SEE ALSO
-
- COLOPHON
-
|
|
- Running on 
-
:
: 