wordexp

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



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 5.04 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/.



                                  2017-09-15                        WORDEXP(3)