wordexp(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | VERSIONS | ATTRIBUTES | CONFORMING TO | EXAMPLES | SEE ALSO | COLOPHON

WORDEXP(3)              Linux Programmer's Manual             WORDEXP(3)

NAME         top

       wordexp, wordfree - perform word expansion like a posix-shell

SYNOPSIS         top

       #include <wordexp.h>

       int wordexp(const char *restrict s, wordexp_t *restrict p, int flags);
       void wordfree(wordexp_t *p);

   Feature Test Macro Requirements for glibc (see
   feature_test_macros(7)):

       wordexp(), wordfree():
           _XOPEN_SOURCE

DESCRIPTION         top

       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         top

       On success, wordexp() returns 0.  On failure, wordexp() returns
       one of the following nonzero values:

       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         top

       wordexp() and wordfree() are provided in glibc since version 2.1.

ATTRIBUTES         top

       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         top

       POSIX.1-2001, POSIX.1-2008.

EXAMPLES         top

       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;

           wordexp("[a-c]*.c", &p, 0);
           w = p.we_wordv;
           for (int i = 0; i < p.we_wordc; i++)
               printf("%s\n", w[i]);
           wordfree(&p);
           exit(EXIT_SUCCESS);
       }

SEE ALSO         top

       fnmatch(3), glob(3)

COLOPHON         top

       This page is part of release 5.12 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/.

                               2021-03-22                     WORDEXP(3)

Pages that refer to this page: fnmatch(3)glob(3)