STRTOK

NAME

SYNOPSIS

#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  

DESCRIPTION

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 non-empty 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.  

RETURN VALUE

CONFORMING TO

strtok()

SVr4, POSIX.1-2001, 4.3BSD, C89, C99.

strtok_r()

POSIX.1-2001.

BUGS

*

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.

EXAMPLE

An example of the output produced by this program is the following:

$ ./a.out aqa/bbb///cc;xxx:yyy:aq aq:;aq aq/aq
1: a/bbb///cc
         --> a
         --> bbb
         --> cc
2: xxx
         --> xxx
3: yyy
         --> yyy

Program source

#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);
} /* main */

SEE ALSO

COLOPHON