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

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() Method:  Splits str[] according to given delimiters and returns the 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);

Example:

C

#include& lt; stdio.h & gt;

#include& lt; string.h & gt;

 

int main()

{

    char str[] = "Geeks-for-Geeks"

    ;

 

    

    char* token = strtok(str, " - ");

 

    

    

    while (token != NULL) {

        printf(" % s\n & quot;, 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() :
 

CPP

#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

Example 2 

C

#include <stdio.h>

#include <string.h>

 

int main()

{

    

    char gfg[100] = " Geeks - for - geeks - Contribute";

 

    

    const char s[4] = "-";

    char* tok;

 

    

    

    tok = strtok(gfg, s);

 

    

    while (tok != 0) {

        printf(" %s\n", tok);

 

        

        

        tok = strtok(0, s);

    }

 

    return (0);

}

Output: 

Geeks
for
geeks
Contribute

Practical Application: strtok can be used to split a string in multiple strings based on some separators. A simple CSV file support might be implemented using this function. CSV files have commas as delimiters.

Example:

C

#include <stdio.h>

#include <string.h>

 

int main()

{

    

    

    char gfg[100] = " 1997 Ford E350 ac 3000.00";

 

    

    const char s[4] = " ";

    char* tok;

 

    

    

    tok = strtok(gfg, s);

 

    

    while (tok != 0) {

        printf("%s, ", tok);

 

        

        

        tok = strtok(0, s);

    }

 

    return (0);

}

Output: 

1997, Ford, E350, ac, 3000.00,

Let us see the differences in a tabular form as shown below as follows: 

strtok() strtok_r() It is used to break string str into a series of tokensIt is used to decode a string into a pattern for tokens.

The syntax is as follows:

char *strtok(char *str, const char *delim)

Its syntax is as follows:
char *strtok_r(char *string, const char *limiter, char **context);It uses the delimiter to proceed.It is a re-entered variant of strtok().It takes two parameters.It takes three parameters.Its return value is a pointer to the first token found in the stringIt is defined in header file <string.h>

This article is contributed by MAZHAR IMAM KHAN and shantanu_23. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to [email protected]. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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