strtok() and strtok_r() functions in C with examples

C provides two functions strtok() and strtok_r() for splitting a string by some delimiter. Splitting a string is a very common task. For example, we have a comma separated list of items from a file and we want individual items in an array.


// Splits str[] according to given delimiters.
// and returns next token. It needs to be called
// in a loop to get all tokens. It returns NULL
// when there are no more tokens.
char * strtok(char str[], const char *delims);
// A C/C++ program for splitting a string
// using strtok()
#include <stdio.h>
#include <string.h>

int main()
    char str[] = "Geeks-for-Geeks";

    // Returns first token 
    char *token = strtok(str, "-");
    // Keep printing tokens while one of the
    // delimiters present in str[].
    while (token != NULL)
        printf("%s\n", token);
        token = strtok(NULL, "-");

    return 0;




Just like strtok() function in C, strtok_r() does the same task of parsing a string into a sequence of tokens. strtok_r() is a reentrant version of strtok()

There are two ways we can call strtok_r()

// The third argument saveptr 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.
char *strtok_r(char *str, const char *delim, char **saveptr);

Below is a simple C program to show the use of strtok_r() :

// C program to demonstrate working of strtok_r()
// by splitting string based on space character.

int main()
    char str[] = "Geeks for Geeks";
    char *token;
    char *rest = str;

    while ((token = strtok_r(rest, " ", &rest)))
        printf("%s\n", token);




1) manual page strtok_r()

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