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.

strtok()

// 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;
}

Output:

Geeks
for
Geeks

strtok_r()

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.
#include<stdio.h>
#include<string.h>

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

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

    return(0);
}

Output:

Geeks
for
Geeks

Reference:
1) manual page strtok_r()
2) http://stackoverflow.com/questions/15961253/c-correct-usage-of-strtok-r

This article is contributed by MAZHAR IMAM KHAN. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

GATE CS Corner    Company Wise Coding Practice





Writing code in comment? Please use code.geeksforgeeks.org, generate link and share the link here.