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

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

C offer various strtok() and strtok r() methods for a string to be separated by a certain delimiter. Dividing a string is a simple task. We have a comma-separated number of stuff from a chart, for instance, but we want separate parts in an array.

Parameters

Str: This string's values are changed and split into small strings.

delim: This is the boundary-containing string C. Those can vary from call to call.

Return Value

Its function returns a reference to the first token in the string that was identified. When there are no tokens remaining to retrieve, a null pointer is returned.

strtok()

Example:

The example below demonstrates the usage of the strtok() method.

#include <string.h>
#include <stdio.h>
int main () {
   char str[80] = "Hello - www.Tutorialandexample.com";
   const char k[2] = "-";
   char *token;
   token = strtok(str, k);
   /* walk through other tokens */
   while( token != NULL ) {
      printf( " %s\n", token );
      token = strtok(NULL, k);
   }
   return(0);
}

Output:

strtok_r()

Relevant to strtok() in C, strtok r() does the same job of decoding a string into a pattern for tokens. Strtok r() is a re-entered variant of strtok().

There are two ways we can call strtok_r()

A third saveptr argument is a char-pointer *
Variable which strtok r() uses internally in
Keep context between subsequent calls
Parse that same string.
Char * strtok r(char * str, * delim, char * * saveptr) const char;

Below is a simple C program displaying when to use 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[] = "Tutorial and example";
    char* token;
    char* rest = str;
    while ((token = strtok_r(rest, " ", &rest)))
        printf("%s\n", token);
    return (0);
}

Output:

Another Example of strtok :

// C code to demonstrate working of
// strtok
#include <stdio.h>
#include <string.h>
// Driver function
int main()
{
          // Declaration of string
          char gfg[100] = " Tutorial - and - example -";
          // Declaration of delimiter
          const char k[4] = "-";
          char* tok;
          // Use of strtok
          // get first token
          tok = strtok(gfg, k);
          // Checks for delimeter
          while (tok != 0) {
                   printf(" %s\n", tok);
                   // Use of strtok
                   // go through other tokens
                   tok = strtok(0, k);
          }
          return (0);
}

Output:

Practical Application

Based on some extractors, strtok could be used to split a string into multiple strings. And use this feature, simple support for CSV files might be implemented. CSV files are delimited with commas.

Example:

// C code to demonstrate the practical application of
#include <stdio.h>
#include <string.h>
// Driver function
int main()
{
          char gfg[100] = " 1998 Ford E370 AC 3000.";
          const char k[4] = " ";
          char* tok;
          tok = strtok(gfg, k);
          while (tok != 0) {
                   printf("%s, ", tok);
                   tok = strtok(0, k);
          }
          return (0);
}

Output: