strtok

strtok, strtok_r - extract tokens from strings

#include <string.h>
 I char *strtok(char * str , const char * delim );
 I char *strtok_r(char * str , const char * delim , char ** saveptr );

The R strtok () function parses a string into a sequence of tokens. On the first call to R 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 R 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, R 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 R strtok () are always non-empty strings. The R strtok_r () function is a reentrant version R strtok (). The saveptr argument is a pointer to a char * variable that is used internally by R strtok_r () in order to maintain context between successive calls that parse the same string. On the first call to R 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 R strtok_r () that specify different saveptr arguments.

The R strtok () and R strtok_r () functions return a pointer to the next token, or NULL if there are no more tokens.

R strtok ()

R strtok_r ()

Avoid using these functions. If you do use them, note that:

These functions cannot be used on constant strings.

The identity of the delimiting character is lost.

The R strtok () function uses a static buffer while parsing, so it's not thread safe. Use R strtok_r () if this matters to you.

The following program uses nested loops that employ R 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.

#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);
} /* main */

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

index(3), memchr(3), rindex(3), strchr(3), strpbrk(3), strsep(3), strspn(3), strstr(3), wcstok(3)