| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | CONFORMING TO | BUGS | EXAMPLE | SEE ALSO | COLOPHON | The Linux Programming Interface |
STRTOK(3) Linux Programmer's Manual STRTOK(3)
strtok, strtok_r - extract tokens from strings
#include <string.h>
char *strtok(char *str, const char *delim);
char *strtok_r(char *str, const char *delim, char **saveptr);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
strtok_r(): _SVID_SOURCE || _BSD_SOURCE || _POSIX_C_SOURCE >= 1 ||
_XOPEN_SOURCE || _POSIX_SOURCE
The strtok() function parses a string into a sequence of tokens. On the first
call to strtok() the string to be parsed should be specified in str. In each
subsequent call that should parse the same string, str should be NULL.
The delim argument specifies a set of characters that delimit the tokens in
the parsed string. The caller may specify different strings in delim in
successive calls that parse the same string.
Each call to strtok() returns a pointer to a null-terminated string containing
the next token. This string does not include the delimiting character. If no
more tokens are found, strtok() returns NULL.
A sequence of two or more contiguous delimiter characters in the parsed string
is considered to be a single delimiter. Delimiter characters at the start or
end of the string are ignored. Put another way: the tokens returned by
strtok() are always nonempty strings.
The strtok_r() function is a reentrant version strtok(). The saveptr argument
is a pointer to a char * variable that is used internally by strtok_r() in
order to maintain context between successive calls that parse the same string.
On the first call to strtok_r(), str should point to the string to be parsed,
and the value of saveptr is ignored. In subsequent calls, str should be NULL,
and saveptr should be unchanged since the previous call.
Different strings may be parsed concurrently using sequences of calls to
strtok_r() that specify different saveptr arguments.
The strtok() and strtok_r() functions return a pointer to the next token, or
NULL if there are no more tokens.
strtok()
SVr4, POSIX.1-2001, 4.3BSD, C89, C99.
strtok_r()
POSIX.1-2001.
Be cautious when using these functions. If you do use them, note that:
* These functions modify their first argument.
* These functions cannot be used on constant strings.
* The identity of the delimiting character is lost.
* The strtok() function uses a static buffer while parsing, so it's not thread
safe. Use strtok_r() if this matters to you.
The program below uses nested loops that employ strtok_r() to break a string
into a two-level hierarchy of tokens. The first command-line argument
specifies the string to be parsed. The second argument specifies the
delimiter character(s) to be used to separate that string into "major" tokens.
The third argument specifies the delimiter character(s) to be used to separate
the "major" tokens into subtokens.
An example of the output produced by this program is the following:
$ ./a.out 'a/bbb///cc;xxx:yyy:' ':;' '/'
1: a/bbb///cc
--> a
--> bbb
--> cc
2: xxx
--> xxx
3: yyy
--> yyy
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int
main(int argc, char *argv[])
{
char *str1, *str2, *token, *subtoken;
char *saveptr1, *saveptr2;
int j;
if (argc != 4) {
fprintf(stderr, "Usage: %s string delim subdelim\n",
argv[0]);
exit(EXIT_FAILURE);
}
for (j = 1, str1 = argv[1]; ; j++, str1 = NULL) {
token = strtok_r(str1, argv[2], &saveptr1);
if (token == NULL)
break;
printf("%d: %s\n", j, token);
for (str2 = token; ; str2 = NULL) {
subtoken = strtok_r(str2, argv[3], &saveptr2);
if (subtoken == NULL)
break;
printf(" --> %s\n", subtoken);
}
}
exit(EXIT_SUCCESS);
}
Another example program using strtok() can be found in getaddrinfo_a(3).
index(3), memchr(3), rindex(3), strchr(3), string(3), strpbrk(3), strsep(3),
strspn(3), strstr(3), wcstok(3)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 2010-09-27 STRTOK(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface