1STRTOK(3P) POSIX Programmer's Manual STRTOK(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 strtok, strtok_r - split string into tokens
13
15 #include <string.h>
16 char *strtok(char *restrict s1, const char *restrict s2);
18 char *strtok_r(char *restrict s, const char *restrict sep,
21 char **restrict lasts);
22
25 For strtok(): The functionality described on this reference page is
26 aligned with the ISO C standard. Any conflict between the requirements
27 described here and the ISO C standard is unintentional. This volume of
28 IEEE Std 1003.1-2001 defers to the ISO C standard.
29 A sequence of calls to strtok() breaks the string pointed to by s1 into
31 a sequence of tokens, each of which is delimited by a byte from the
32 string pointed to by s2. The first call in the sequence has s1 as its
33 first argument, and is followed by calls with a null pointer as their
34 first argument. The separator string pointed to by s2 may be different
35 from call to call.
36 The first call in the sequence searches the string pointed to by s1 for
38 the first byte that is not contained in the current separator string
39 pointed to by s2. If no such byte is found, then there are no tokens in
40 the string pointed to by s1 and strtok() shall return a null pointer.
41 If such a byte is found, it is the start of the first token.
42 The strtok() function then searches from there for a byte that is con‐
44 tained in the current separator string. If no such byte is found, the
45 current token extends to the end of the string pointed to by s1, and
46 subsequent searches for a token shall return a null pointer. If such a
47 byte is found, it is overwritten by a null byte, which terminates the
48 current token. The strtok() function saves a pointer to the following
49 byte, from which the next search for a token shall start.
50 Each subsequent call, with a null pointer as the value of the first
52 argument, starts searching from the saved pointer and behaves as
53 described above.
54 The implementation shall behave as if no function defined in this vol‐
56 ume of IEEE Std 1003.1-2001 calls strtok().
57 The strtok() function need not be reentrant. A function that is not
59 required to be reentrant is not required to be thread-safe.
60 The strtok_r() function considers the null-terminated string s as a
62 sequence of zero or more text tokens separated by spans of one or more
63 characters from the separator string sep. The argument lasts points to
64 a user-provided pointer which points to stored information necessary
65 for strtok_r() to continue scanning the same string.
66 In the first call to strtok_r(), s points to a null-terminated string,
68 sep to a null-terminated string of separator characters, and the value
69 pointed to by lasts is ignored. The strtok_r() function shall return a
70 pointer to the first character of the first token, write a null charac‐
71 ter into s immediately following the returned token, and update the
72 pointer to which lasts points.
73 In subsequent calls, s is a NULL pointer and lasts shall be unchanged
75 from the previous call so that subsequent calls shall move through the
76 string s, returning successive tokens until no tokens remain. The sepa‐
77 rator string sep may be different from call to call. When no token
78 remains in s, a NULL pointer shall be returned.
79
81 Upon successful completion, strtok() shall return a pointer to the
82 first byte of a token. Otherwise, if there is no token, strtok() shall
83 return a null pointer.
84 The strtok_r() function shall return a pointer to the token found, or a
86 NULL pointer when no token is found.
87
89 No errors are defined.
90 The following sections are informative.
92
94 Searching for Word Separators
95 The following example searches for tokens separated by <space>s.
96 #include <string.h>
99 ...
100 char *token;
101 char *line = "LINE TO BE SEPARATED";
102 char *search = " ";
103 /* Token will point to "LINE". */
106 token = strtok(line, search);
107 /* Token will point to "TO". */
110 token = strtok(NULL, search);
111 Breaking a Line
113 The following example uses strtok() to break a line into two character
114 strings separated by any combination of <space>s, <tab>s, or <new‐
115 line>s.
116 #include <string.h>
119 ...
120 struct element {
121 char *key;
122 char *data;
123 };
124 ...
125 char line[LINE_MAX];
126 char *key, *data;
127 ...
128 key = strtok(line, " \n");
129 data = strtok(NULL, " \n");
130 ...
131
133 The strtok_r() function is thread-safe and stores its state in a user-
134 supplied buffer instead of possibly using a static data area that may
135 be overwritten by an unrelated call from another thread.
136
138 The strtok() function searches for a separator string within a larger
139 string. It returns a pointer to the last substring between separator
140 strings. This function uses static storage to keep track of the current
141 string position between calls. The new function, strtok_r(), takes an
142 additional argument, lasts, to keep track of the current position in
143 the string.
144
146 None.
147
149 The Base Definitions volume of IEEE Std 1003.1-2001, <string.h>
150
152 Portions of this text are reprinted and reproduced in electronic form
153 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
154 -- Portable Operating System Interface (POSIX), The Open Group Base
155 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
156 Electrical and Electronics Engineers, Inc and The Open Group. In the
157 event of any discrepancy between this version and the original IEEE and
158 The Open Group Standard, the original IEEE and The Open Group Standard
159 is the referee document. The original Standard can be obtained online
160 at http://www.opengroup.org/unix/online.html .
161IEEE/The Open Group 2003 STRTOK(3P)