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() 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);
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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() :
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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.
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Let us see the differences in a tabular form as shown below as follows:
|It is used to break string str into a series of tokens||It 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 string||It is defined in header file <string.h>|
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