wordexp(3) - NetBSD Manual Pages

WORDEXP(3)              NetBSD Library Functions Manual             WORDEXP(3)


NAME

     wordexp -- perform shell-style word expansions


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <wordexp.h>

     int
     wordexp(const char * restrict words, wordexp_t * restrict pwordexp,
         int flags);

     void
     wordfree(wordexp_t *pwordexp);


DESCRIPTION

     The wordexp() function performs shell-style word expansion on words and
     places the list of expanded words into the structure pointed to by
     pwordexp.

     The flags argument is the bitwise inclusive OR of any of the following
     constants:

     WRDE_APPEND   Append the words to those generated by a previous call to
                   wordexp().

     WRDE_DOOFFS   As many NULL pointers as are specified by the we_offs mem-
                   ber of we are added to the front of we_wordv.

     WRDE_NOCMD    Disallow command substitution in words.  See the note in
                   BUGS before using this.

     WRDE_REUSE    The we argument was passed to a previous successful call to
                   wordexp() but has not been passed to wordfree().  The
                   implementation may reuse the space allocated to it.

     WRDE_SHOWERR  Do not redirect shell error messages to /dev/null.

     WRDE_UNDEF    Report error on an attempt to expand an undefined shell
                   variable.

     The structure type wordexp_t includes the following members:

           size_t  we_wordc
           char    **we_wordv
           size_t  we_offs

     The we_wordc member is the count of generated words.

     The we_wordv member points to a list of pointers to expanded words.

     The we_offs member is the number of slots to reserve at the beginning of
     the we_wordv member.

     It is the caller's responsibility to allocate the storage pointed to by
     pwordexp.  The wordexp() function allocates other space as needed,
     including memory pointed to by the we_wordv member.

     The wordfree() function frees the memory allocated by wordexp().


IMPLEMENTATION NOTES

     The wordexp() function is implemented as a wrapper around the undocu-
     mented wordexp shell built-in command.


RETURN VALUES

     The wordexp() function returns zero if successful, otherwise it returns
     one of the following error codes:

     WRDE_BADCHAR  The words argument contains one of the following unquoted
                   characters: <newline>, `|', `&', `;', `<', `>', `(', `)',
                   `{', `}'.

     WRDE_BADVAL   An attempt was made to expand an undefined shell variable
                   and WRDE_UNDEF is set in flags.

     WRDE_CMDSUB   An attempt was made to use command substitution and
                   WRDE_NOCMD is set in flags.

     WRDE_NOSPACE  Not enough memory to store the result.

     WRDE_SYNTAX   Shell syntax error in words.

     WRDE_ERRNO    An internal error occurred and errno is set to indicate the
                   error.

     The wordfree() function returns no value.


ENVIRONMENT

     IFS  Field separator.


EXAMPLES

     Invoke the editor on all .c files in the current directory and /etc/motd
     (error checking omitted):

           wordexp_t we;

           wordexp("${EDITOR:-vi} *.c /etc/motd", &we, 0);
           execvp(we->we_wordv[0], we->we_wordv);


DIAGNOSTICS

     Diagnostic messages from the shell are written to the standard error out-
     put if WRDE_SHOWERR is set in flags.


SEE ALSO

     sh(1), fnmatch(3), glob(3), popen(3), system(3)


STANDARDS

     The wordexp() and wordfree() functions conform to IEEE Std 1003.1-2001
     (``POSIX.1'').  Their first release was in IEEE Std 1003.2-1992
     (``POSIX.2'').  The return value WRDE_ERRNO is an extension.


BUGS

     Do not pass untrusted user data to wordexp(), regardless of whether the
     WRDE_NOCMD flag is set.  The wordexp() function attempts to detect input
     that would cause commands to be executed before passing it to the shell
     but it does not use the same parser so it may be fooled.

NetBSD 10.99                     July 13, 2004                    NetBSD 10.99