1wordexp(3C) Standard C Library Functions wordexp(3C)
2
6 wordexp, wordfree - perform word expansions
7
9 #include <wordexp.h>
10 int wordexp(const char *restrict words, wordexp_t *restrict pwordexp,
12 int flags);
13 void wordfree(wordexp_t *pwordexp);
16
19 The wordexp() function performs word expansions, subject to quoting,
20 and places the list of expanded words into the structure pointed to by
21 pwordexp.
22 The wordfree() function frees any memory allocated by wordexp() associ‐
25 ated with pwordexp.
26 words Argument
28 The words argument is a pointer to a string containing one or more
29 words to be expanded. The expansions will be the same as would be per‐
30 formed by the shell if words were the part of a command line represent‐
31 ing the arguments to a utility. Therefore, words must not contain an
32 unquoted NEWLINE or any of the unquoted shell special characters:
33 | & ; < >
36 except in the context of command substitution. It also must not contain
39 unquoted parentheses or braces, except in the context of command or
40 variable substitution. If the argument words contains an unquoted com‐
41 ment character (number sign) that is the beginning of a token, word‐
42 exp() may treat the comment character as a regular character, or may
43 interpret it as a comment indicator and ignore the remainder of words.
44 pwordexp Argument
46 The structure type wordexp_t is defined in the header <wordexp.h> and
47 includes at least the following members:
48 size_t we_wordc Count of words matched by words.
50 char **we_wordv Pointer to list of expanded words.
53 size_t we_offs Slots to reserve at the beginning of pword‐
56 exp−>we_wordv.
57 The wordexp() function stores the number of generated words into pword‐
61 exp−>we_wordc and a pointer to a list of pointers to words in pword‐
62 exp−>we_wordv. Each individual field created during field splitting is
63 a separate word in the pwordexp−>we_wordv list. The words are in
64 order. The first pointer after the last word pointer will be a null
65 pointer.
66 It is the caller's responsibility to allocate the storage pointed to by
69 pwordexp. The wordexp() function allocates other space as needed,
70 including memory pointed to by pwordexp−>we_wordv. The wordfree() func‐
71 tion frees any memory associated with pwordexp from a previous call to
72 wordexp().
73 flags Argument
75 The flags argument is used to control the behavior of wordexp(). The
76 value of flags is the bitwise inclusive OR of zero or more of the fol‐
77 lowing constants, which are defined in <wordexp.h>:
78 WRDE_APPEND Append words generated to the ones from a previous call
80 to wordexp().
81 WRDE_DOOFFS Make use of pwordexp−>we_offs. If this flag is set,
84 pwordexp−>we_offs is used to specify how many NULL
85 pointers to add to the beginning of pwordexp−>we_wordv.
86 In other words, pwordexp−>we_wordv will point to pword‐
87 exp−>we_offs NULL pointers, followed by pword‐
88 exp−>we_wordc word pointers, followed by a NULL
89 pointer.
90 WRDE_NOCMD Fail if command substitution is requested.
93 WRDE_REUSE The pwordexp argument was passed to a previous success‐
96 ful call to wordexp(), and has not been passed to word‐
97 free(). The result will be the same as if the applica‐
98 tion had called wordfree() and then called wordexp()
99 without WRDE_REUSE.
100 WRDE_SHOWERR Do not redirect stderr to /dev/null.
103 WRDE_UNDEF Report error on an attempt to expand an undefined shell
106 variable.
107 The WRDE_APPEND flag can be used to append a new set of words to those
111 generated by a previous call to wordexp(). The following rules apply
112 when two or more calls to wordexp() are made with the same value of
113 pwordexp and without intervening calls to wordfree():
114 1. The first such call must not set WRDE_APPEND. All subsequent
116 calls must set it.
117 2. All of the calls must set WRDE_DOOFFS, or all must not set
119 it.
120 3. After the second and each subsequent call, pword‐
122 exp−>we_wordv will point to a list containing the following:
123 a. zero or more NULL pointers, as specified by WRDE_DOOFFS
125 and pwordexp−>we_offs.
126 b. pointers to the words that were in the pword‐
128 exp−>we_wordv list before the call, in the same order as
129 before.
130 c. pointers to the new words generated by the latest call,
132 in the specified order.
133 4. The count returned in pwordexp−>we_wordc will be the total
135 number of words from all of the calls.
136 5. The application can change any of the fields after a call to
138 wordexp(), but if it does it must reset them to the original
139 value before a subsequent call, using the same pwordexp
140 value, to wordfree() or wordexp() with the WRDE_APPEND or
141 WRDE_REUSE flag.
142 If words contains an unquoted:
145 NEWLINE | & ; < > ( ) { }
148 in an inappropriate context, wordexp() will fail, and the number of
151 expanded words will be zero.
152 Unless WRDE_SHOWERR is set in flags, wordexp() will redirect stderr to
155 /dev/null for any utilities executed as a result of command substitu‐
156 tion while expanding words.
157 If WRDE_SHOWERR is set, wordexp() may write messages to stderr if syn‐
160 tax errors are detected while expanding words. If WRDE_DOOFFS is set,
161 then pwordexp−> we_offs must have the same value for each wordexp()
162 call and wordfree() call using a given pwordexp.
163 The following constants are defined as error return values:
166 WRDE_BADCHAR One of the unquoted characters:
168 NEWLINE | & ; < > ( ) { }
170 appears in words in an inappropriate context.
172 WRDE_BADVAL Reference to undefined shell variable when WRDE_UNDEF
175 is set in flags.
176 WRDE_CMDSUB Command substitution requested when WRDE_NOCMD was set
179 in flags.
180 WRDE_NOSPACE Attempt to allocate memory failed.
183 WRDE_SYNTAX Shell syntax error, such as unbalanced parentheses or
186 unterminated string.
187
190 On successful completion, wordexp() returns 0.
191 Otherwise, a non-zero value as described in <wordexp.h> is returned to
194 indicate an error. If wordexp() returns the value WRDE_NOSPACE, then
195 pwordexp−>we_wordc and pwordexp−>we_wordv will be updated to reflect
196 any words that were successfully expanded. In other cases, they will
197 not be modified.
198 The wordfree() function returns no value.
201
203 No errors are defined.
204
206 This function is intended to be used by an application that wants to do
207 all of the shell's expansions on a word or words obtained from a user.
208 For example, if the application prompts for a filename (or list of
209 filenames) and then uses wordexp() to process the input, the user could
210 respond with anything that would be valid as input to the shell.
211 The WRDE_NOCMD flag is provided for applications that, for security or
214 other reasons, want to prevent a user from executing shell command.
215 Disallowing unquoted shell special characters also prevents unwanted
216 side effects such as executing a command or writing a file.
217
219 See attributes(5) for descriptions of the following attributes:
220 ┌─────────────────────────────┬─────────────────────────────┐
225 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
226 ├─────────────────────────────┼─────────────────────────────┤
227 │Interface Stability │Standard │
228 ├─────────────────────────────┼─────────────────────────────┤
229 │MT-Level │MT-Safe │
230 └─────────────────────────────┴─────────────────────────────┘
231
233 fnmatch(3C), glob(3C), attributes(5), standards(5)
234SunOS 5.11 1 Nov 2003 wordexp(3C)