Manpage of WORDEXP

WORDEXP

Section: Linux Programmer's Manual (3)
Updated: 2016-10-08
Index
 

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 sand returns the result in the structure pointed to by p. The data type wordexp_tis a structure that at least has the fields we_wordc, we_wordv, and we_offs. The field we_wordcis a size_tthat gives the number of words in the expansion of s. The field we_wordvis a char **that points to the array of words found. The field we_offsof type size_tis sometimes (depending on flags, see below) used to indicate the number of initial elements in the we_wordvarray 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_wordvand 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 smust 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 scontains 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_wordvcontains the words found, followed by a NULL.  

The flags argument

The flagargument 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_offsinitial 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 presulted from a previous call to wordexp(), and wordfree() was not called. Reuse the allocated storage.
WRDE_SHOWERR
Normally during command substitution stderris redirected to /dev/null. This flag specifies that stderris 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_UNDEFflag told us to consider this an error.
WRDE_CMDSUB
Command substitution requested, but the WRDE_NOCMDflag 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).
InterfaceAttributeValue
wordexp() Thread safetyMT-Unsafe race:utent const:env
env sig:ALRM timer locale
wordfree() Thread safetyMT-Safe

In the above table, utentin race:utentsignifies 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)


 

Index

NAME
SYNOPSIS
DESCRIPTION
The string argument
The expansion
The output array
The flags argument
RETURN VALUE
VERSIONS
ATTRIBUTES
CONFORMING TO
EXAMPLE
SEE ALSO

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