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


     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);
 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
     wordexp(), wordfree(): _XOPEN_SOURCE


     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 pre-
     cisely, 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 par-
     ticular, there must not be any unescaped newline or |, &, ;, <,  >,  (,
     ),  {, } characters outside a command substitution or parameter substi-
     tution 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  $(command) or `command` by the output of com-
     mand), arithmetic expansion, field splitting, wildcard expansion, quote
     The  result of expansion of special parameters ($@, $*, $#, $?, $-, $$,
     $!, $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:
            Append  the  words  found to the array resulting from a previous
            Insert we_offs initial NULLs in the array we_wordv.  (These  are
            not counted in the returned we_wordc.)
            Don't do command substitution.
            The  argument  p resulted from a previous call to wordexp(), and
            wordfree() was not called.  Reuse the allocated storage.
            Normally during command substitution  stderr  is  redirected  to
            /dev/null.   This  flag specifies that stderr is not to be redi-
            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 follow-
     ing five values is returned.
            Illegal occurrence of newline or one of |, &, ;, <, >, (, ),  {,
            An  undefined  shell variable was referenced, and the WRDE_UNDEF
            flag told us to consider this an error.
            Command substitution requested, but the WRDE_NOCMD flag told  us
            to consider this an error.
            Out of memory.
            Shell  syntax error, such as unbalanced parentheses or unmatched


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


     For  an  explanation  of  the  terms  used   in   this   section,   see
     |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.   word-
     exp() calls those functions, so we use race:utent to remind users.


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


     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]);
         exit(EXIT_SUCCESS); }


     fnmatch(3), glob(3)


     This page is part of release 4.16 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
                                2017-09-15                        WORDEXP(3)
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