1WORDEXP(3) Linux Programmer's Manual WORDEXP(3)
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6 wordexp, wordfree - perform word expansion like a posix-shell
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9 #include <wordexp.h>
10 int wordexp(const char *s, wordexp_t *p, int flags);
12 void wordfree(wordexp_t *p);
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17 The function wordexp() performs a shell-like expansion of the string s
18 and returns the result in the structure pointed to by p. The data type
19 wordexp_t is a structure that at least has the fields we_wordc,
20 we_wordv, and we_offs. The field we_wordc is a size_t that gives the
21 number of words in the expansion of s. The field we_wordv is a char **
22 that points to the array of words found. The field we_offs of type
23 size_t is sometimes (depending on flags, see below) used to indicate
24 the number of initial elements in the we_wordv array that should be
25 filled with NULLs.
26 The function wordfree() frees the allocated memory again. More pre‐
28 cisely, it does not free its argument, but it frees the array we_wordv
29 and the strings that points to.
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33 First a small example. The output is approximately that of "ls [a-
34 c]*.c".
35 #include <stdio.h>
37 #include <wordexp.h>
38 int main(int argc, char **argv) {
40 wordexp_t p;
41 char **w;
42 int i;
43 wordexp("[a-c]*.c", &p, 0);
45 w = p.we_wordv;
46 for (i=0; i<p.we_wordc; i++)
47 printf("%s\n", w[i]);
48 wordfree(&p);
49 return 0;
50 }
51
53 The string argument
54 Since the expansion is the same as the expansion by the shell (see
55 sh(1)) of the parameters to a command, the string s must not contain
56 characters that would be illegal in shell command parameters. In par‐
57 ticular, there must not be any non-escaped newline or |, &, ;, <, >, (,
58 ), {, } characters outside a command substitution or parameter substi‐
59 tution context.
60 If the argument s contains a word that starts with an unquoted comment
62 character #, then it is unspecified whether that word and all following
63 words are ignored, or the # is treated as a non-comment character.
64 The expansion
67 The expansion done consists of the following stages: tilde expansion
68 (replacing ~user by user's home directory), variable substitution
69 (replacing $FOO by the value of the environment variable FOO), command
70 substitution (replacing $(command) or `command` by the output of com‐
71 mand), arithmetic expansion, field splitting, wildcard expansion, quote
72 removal.
73 The result of expansion of special parameters ($@, $*, $#, $?, $-, $$,
75 $!, $0) is unspecified.
76 Field splitting is done using the environment variable $IFS. If it is
78 not set, the field separators are space, tab and newline.
79 The output array
82 The array we_wordv contains the words found, followed by a NULL.
83 The flags argument
86 The flag argument is a bitwise inclusive OR of the following values:
87 WRDE_APPEND
89 Append the words found to the array resulting from a previous
90 call.
91 WRDE_DOOFFS
93 Insert we_offs initial NULLs in the array we_wordv. (These are
94 not counted in the returned we_wordc.)
95 WRDE_NOCMD
97 Don't do command substitution.
98 WRDE_REUSE
100 The parameter p resulted from a previous call to wordexp(), and
101 wordfree() was not called. Reuse the allocated storage.
102 WRDE_SHOWERR
104 Normally during command substitution stderr is redirected to
105 /dev/null. This flag specifies that stderr is not to be redi‐
106 rected.
107 WRDE_UNDEF
109 Consider it an error if an undefined shell variable is expanded.
110
112 In case of success 0 is returned. In case of error one of the following
113 five values is returned.
114 WRDE_BADCHAR
116 Illegal occurrence of newline or one of |, &, ;, <, >, (, ), {,
117 }.
118 WRDE_BADVAL
120 An undefined shell variable was referenced, and the WRDE_UNDEF
121 flag told us to consider this an error.
122 WRDE_CMDSUB
124 Command substitution occurred, and the WRDE_NOCMD flag told us
125 to consider this an error.
126 WRDE_NOSPACE
128 Out of memory.
129 WRDE_SYNTAX
131 Shell syntax error, such as unbalanced parentheses or unmatched
132 quotes.
133
136 POSIX.1-2001
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140 fnmatch(3), glob(3)
141 2003-11-11 WORDEXP(3)