2 .\" Copyright (C) 2005, 2013 Michael Kerrisk <mtk.manpages@gmail.com>
3 .\" a few fragments from an earlier (1996) version by
4 .\" Andries Brouwer (aeb@cwi.nl) remain.
6 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
8 .\" Rewritten old page, 960210, aeb@cwi.nl
9 .\" Updated, added strtok_r. 2000-02-13 Nicolás Lichtmaier <nick@debian.org>
10 .\" 2005-11-17, mtk: Substantial parts rewritten
11 .\" 2013-05-19, mtk: added much further detail on the operation of strtok()
13 .TH strtok 3 (date) "Linux man-pages (unreleased)"
15 strtok, strtok_r \- extract tokens from strings
18 .RI ( libc ", " \-lc )
21 .B #include <string.h>
23 .BI "char *strtok(char *restrict " str ", const char *restrict " delim );
24 .BI "char *strtok_r(char *restrict " str ", const char *restrict " delim ,
25 .BI " char **restrict " saveptr );
29 Feature Test Macro Requirements for glibc (see
30 .BR feature_test_macros (7)):
36 || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
41 function breaks a string into a sequence of zero or more nonempty tokens.
44 the string to be parsed should be
47 In each subsequent call that should parse the same string,
53 argument specifies a set of bytes that
54 delimit the tokens in the parsed string.
55 The caller may specify different strings in
58 calls that parse the same string.
62 returns a pointer to a
63 null-terminated string containing the next token.
64 This string does not include the delimiting byte.
65 If no more tokens are found,
69 A sequence of calls to
71 that operate on the same string maintains a pointer
72 that determines the point from which to start searching for the next token.
75 sets this pointer to point to the first byte of the string.
76 The start of the next token is determined by scanning forward
77 for the next nondelimiter byte in
79 If such a byte is found, it is taken as the start of the next token.
80 If no such byte is found,
81 then there are no more tokens, and
84 (A string that is empty or that contains only delimiters
87 to return NULL on the first call.)
89 The end of each token is found by scanning forward until either
90 the next delimiter byte is found or until the
91 terminating null byte (\[aq]\e0\[aq]) is encountered.
92 If a delimiter byte is found, it is overwritten with
93 a null byte to terminate the current token, and
95 saves a pointer to the following byte;
96 that pointer will be used as the starting point
97 when searching for the next token.
100 returns a pointer to the start of the found token.
102 From the above description,
103 it follows that a sequence of two or more contiguous delimiter bytes in
104 the parsed string is considered to be a single delimiter, and that
105 delimiter bytes at the start or end of the string are ignored.
106 Put another way: the tokens returned by
108 are always nonempty strings.
109 Thus, for example, given the string "\fIaaa;;bbb,\fP",
112 that specify the delimiter string "\fI;,\fP"
113 would return the strings "\fIaaa\fP" and "\fIbbb\fP",
114 and then a null pointer.
118 function is a reentrant version of
122 argument is a pointer to a
124 variable that is used internally by
126 in order to maintain context between successive calls that parse the
132 should point to the string to be parsed, and the value of
134 is ignored (but see NOTES).
139 (and the buffer that it points to)
140 should be unchanged since the previous call.
142 Different strings may be parsed concurrently using sequences of calls to
144 that specify different
152 functions return a pointer to
153 the next token, or NULL if there are no more tokens.
155 For an explanation of the terms used in this section, see
163 Interface Attribute Value
166 T} Thread safety MT-Unsafe race:strtok
169 T} Thread safety MT-Safe
177 POSIX.1-2001, POSIX.1-2008, C99, SVr4, 4.3BSD.
180 POSIX.1-2001, POSIX.1-2008.
182 On some implementations,
183 .\" Tru64, according to its manual page
185 is required to be NULL on the first call to
187 that is being used to parse
190 Be cautious when using these functions.
191 If you do use them, note that:
193 These functions modify their first argument.
195 These functions cannot be used on constant strings.
197 The identity of the delimiting byte is lost.
201 function uses a static buffer while parsing, so it's not thread safe.
204 if this matters to you.
206 The program below uses nested loops that employ
208 to break a string into a two-level hierarchy of tokens.
209 The first command-line argument specifies the string to be parsed.
210 The second argument specifies the delimiter byte(s)
211 to be used to separate that string into "major" tokens.
212 The third argument specifies the delimiter byte(s)
213 to be used to separate the "major" tokens into subtokens.
215 An example of the output produced by this program is the following:
219 .RB "$" " ./a.out \[aq]a/bbb///cc;xxx:yyy:\[aq] \[aq]:;\[aq] \[aq]/\[aq]"
232 .\" SRC BEGIN (strtok.c)
239 main(int argc, char *argv[])
241 char *str1, *str2, *token, *subtoken;
242 char *saveptr1, *saveptr2;
246 fprintf(stderr, "Usage: %s string delim subdelim\en",
251 for (j = 1, str1 = argv[1]; ; j++, str1 = NULL) {
252 token = strtok_r(str1, argv[2], &saveptr1);
255 printf("%d: %s\en", j, token);
257 for (str2 = token; ; str2 = NULL) {
258 subtoken = strtok_r(str2, argv[3], &saveptr2);
259 if (subtoken == NULL)
261 printf("\et \-\-> %s\en", subtoken);
270 Another example program using
273 .BR getaddrinfo_a (3).