strtok_r(3)

NAME
strtok_r - string tokenize reentrant

LIBRARY
Standard C library (libc, -lc)

SYNOPSIS
#include <string.h>

char *strtok_r(char *_Nullable restrict str, const char *restrict delim,
               char **restrict saveptr);

    Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

strtok_r():
    _POSIX_C_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION
The strtok_r() function is a reentrant version of strtok(3).

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 (but see VERSIONS). In subsequent calls, str should be NULL, and saveptr (and the buffer that it points to) 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
strtok_r() returns a pointer to the next token, or NULL if there are no more tokens.

ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
Interface | Attribute | Value
 | Thread safety | MT-Safe

VERSIONS
On some implementations, *saveptr is required to be NULL on the first call to strtok_r() that is being used to parse str.

STANDARDS
POSIX.1-2008.

HISTORY
POSIX.1-2001.

EXAMPLES
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 byte(s) to be used to separate that string into "major" tokens. The third argument specifies the delimiter byte(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

  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("\t --> %s\n", subtoken);
            }
        }

        exit(EXIT_SUCCESS);
    }

SEE ALSO
strtok(3)