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);
C
// 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() :
CPP
// 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
Another Example of strtok :
C
// C code to demonstrate working of// strtok#include <stdio.h>#include <string.h>// Driver functionint main(){ // Declaration of string char gfg[100] = " Geeks - for - geeks - Contribute"; // Declaration of delimiter const char s[4] = "-"; char* tok; // Use of strtok // get first token tok = strtok(gfg, s); // Checks for delimiter while (tok != 0) { printf(" %s\n", tok); // Use of strtok // go through other tokens 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.
C
// C code to demonstrate practical application of// strtok#include <stdio.h>#include <string.h>// Driver functionint main(){ // Declaration of string // Information to be converted into CSV file char gfg[100] = " 1997 Ford E350 ac 3000.00"; // Declaration of delimiter const char s[4] = " "; char* tok; // Use of strtok // get first token tok = strtok(gfg, s); // Checks for delimiter while (tok != 0) { printf("%s, ", tok); // Use of strtok // go through other tokens tok = strtok(0, s); } return (0);} |
Output:
1997, Ford, E350, ac, 3000.00,
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 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 review-team@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.
.png)
