1wordexp(3) Library Functions Manual wordexp(3)
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6 wordexp, wordfree - perform word expansion like a posix-shell
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9 Standard C library (libc, -lc)
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12 #include <wordexp.h>
13 int wordexp(const char *restrict s, wordexp_t *restrict p, int flags);
15 void wordfree(wordexp_t *p);
16 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
18 wordexp(), wordfree():
20 _XOPEN_SOURCE
21
23 The function wordexp() performs a shell-like expansion of the string s
24 and returns the result in the structure pointed to by p. The data type
25 wordexp_t is a structure that at least has the fields we_wordc,
26 we_wordv, and we_offs. The field we_wordc is a size_t that gives the
27 number of words in the expansion of s. The field we_wordv is a char **
28 that points to the array of words found. The field we_offs of type
29 size_t is sometimes (depending on flags, see below) used to indicate
30 the number of initial elements in the we_wordv array that should be
31 filled with NULLs.
32 The function wordfree() frees the allocated memory again. More pre‐
34 cisely, it does not free its argument, but it frees the array we_wordv
35 and the strings that points to.
36 The string argument
38 Since the expansion is the same as the expansion by the shell (see
39 sh(1)) of the parameters to a command, the string s must not contain
40 characters that would be illegal in shell command parameters. In par‐
41 ticular, there must not be any unescaped newline or |, &, ;, <, >, (,
42 ), {, } characters outside a command substitution or parameter substi‐
43 tution context.
44 If the argument s contains a word that starts with an unquoted comment
46 character #, then it is unspecified whether that word and all following
47 words are ignored, or the # is treated as a non-comment character.
48 The expansion
50 The expansion done consists of the following stages: tilde expansion
51 (replacing ~user by user's home directory), variable substitution (re‐
52 placing $FOO by the value of the environment variable FOO), command
53 substitution (replacing $(command) or `command` by the output of com‐
54 mand), arithmetic expansion, field splitting, wildcard expansion, quote
55 removal.
56 The result of expansion of special parameters ($@, $*, $#, $?, $-, $$,
58 $!, $0) is unspecified.
59 Field splitting is done using the environment variable $IFS. If it is
61 not set, the field separators are space, tab, and newline.
62 The output array
64 The array we_wordv contains the words found, followed by a NULL.
65 The flags argument
67 The flag argument is a bitwise inclusive OR of the following values:
68 WRDE_APPEND
70 Append the words found to the array resulting from a previous
71 call.
72 WRDE_DOOFFS
74 Insert we_offs initial NULLs in the array we_wordv. (These are
75 not counted in the returned we_wordc.)
76 WRDE_NOCMD
78 Don't do command substitution.
79 WRDE_REUSE
81 The argument p resulted from a previous call to wordexp(), and
82 wordfree() was not called. Reuse the allocated storage.
83 WRDE_SHOWERR
85 Normally during command substitution stderr is redirected to
86 /dev/null. This flag specifies that stderr is not to be redi‐
87 rected.
88 WRDE_UNDEF
90 Consider it an error if an undefined shell variable is expanded.
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93 On success, wordexp() returns 0. On failure, wordexp() returns one of
94 the following nonzero values:
95 WRDE_BADCHAR
97 Illegal occurrence of newline or one of |, &, ;, <, >, (, ), {,
98 }.
99 WRDE_BADVAL
101 An undefined shell variable was referenced, and the WRDE_UNDEF
102 flag told us to consider this an error.
103 WRDE_CMDSUB
105 Command substitution requested, but the WRDE_NOCMD flag told us
106 to consider this an error.
107 WRDE_NOSPACE
109 Out of memory.
110 WRDE_SYNTAX
112 Shell syntax error, such as unbalanced parentheses or unmatched
113 quotes.
114
116 For an explanation of the terms used in this section, see at‐
117 tributes(7).
118 ┌───────────┬───────────────┬──────────────────────────────────────────┐
120 │Interface │ Attribute │ Value │
121 ├───────────┼───────────────┼──────────────────────────────────────────┤
122 │wordexp() │ Thread safety │ MT-Unsafe race:utent const:env env │
123 │ │ │ sig:ALRM timer locale │
124 ├───────────┼───────────────┼──────────────────────────────────────────┤
125 │wordfree() │ Thread safety │ MT-Safe │
126 └───────────┴───────────────┴──────────────────────────────────────────┘
127 In the above table, utent in race:utent signifies that if any of the
128 functions setutent(3), getutent(3), or endutent(3) are used in parallel
129 in different threads of a program, then data races could occur.
130 wordexp() calls those functions, so we use race:utent to remind users.
131
133 POSIX.1-2008.
134
136 POSIX.1-2001. glibc 2.1.
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139 The output of the following example program is approximately that of
140 "ls [a-c]*.c".
141 #include <stdio.h>
143 #include <stdlib.h>
144 #include <wordexp.h>
145 int
147 main(void)
148 {
149 wordexp_t p;
150 char **w;
151 wordexp("[a-c]*.c", &p, 0);
153 w = p.we_wordv;
154 for (size_t i = 0; i < p.we_wordc; i++)
155 printf("%s\n", w[i]);
156 wordfree(&p);
157 exit(EXIT_SUCCESS);
158 }
159
161 fnmatch(3), glob(3)
162Linux man-pages 6.05 2023-07-20 wordexp(3)