FreeBSD manual
download PDF document: wordexp.3.pdf
WORDEXP(3) FreeBSD 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 we, int flags);
void
wordfree(wordexp_t *we);
DESCRIPTION
The wordexp() function performs shell-style word expansion on words and
places the list of words into the we_wordv member of we, and the number
of words into we_wordc.
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
member 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 wordexp_t structure is defined in <wordexp.h> as:
typedef struct {
size_t we_wordc; /* count of words matched */
char **we_wordv; /* pointer to list of words */
size_t we_offs; /* slots to reserve in we_wordv */
} wordexp_t;
The wordfree() function frees the memory allocated by wordexp().
IMPLEMENTATION NOTES
The wordexp() function is implemented using the undocumented
freebsd_wordexp shell built-in command.
RETURN VALUES
The wordexp() function returns zero if successful, otherwise it returns
expand an undefined shell variable with WRDE_UNDEF 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 or an error during
fork(2).
WRDE_SYNTAX Shell syntax error in words.
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
output 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").
BUGS
The current wordexp() implementation does not recognize multibyte
characters other than UTF-8, since the shell (which it invokes to perform
expansions) does not.
SECURITY CONSIDERATIONS
Pathname generation may create output that is exponentially larger than
the input size.
Although this implementation detects command substitution reliably for
WRDE_NOCMD, the attack surface remains fairly large. Also, some other
implementations (such as older versions of this one) may execute command
substitutions even if WRDE_NOCMD is set.
FreeBSD 14.0-RELEASE-p11 September 30, 2015 FreeBSD 14.0-RELEASE-p11