How to duplicate a string? (String duplication with strdup)

C Programmers often requires obtaining a duplicate string from an original one. This can be achieved by knowing the length of the string and then allocating the buffer for the string and finally copying the content to the allocated buffer.

 
 char * strdup(const char * str)

 {

   int len;

   char * buffer;

   if(!str) {

     return NULL;

   }

   len = strlen(str);

   buffer = (char *) malloc (len + 1);

   strcpy(buffer, str);

   return buffer;

 }

We do not require to do all the steps as C runtime library has strdup() function to do all these for us. Here is a sample example program.

 
 #include <string.h>

 #include <stdio.h>

 int main(int argc, char* argv[])

 {

   int i = 0;

   const char *str = "A Quick Brown Fox Jumps over the lazy dog.";

   char *tokens, *token;

   tokens = strdup(str);

   token = strtok(tokens, );

   while(token) {

     printf("Token %d: %s\n", i + 1, token);

     token = strtok(NULL, " .");

     i++;

   }

   free(tokens);

   return 0;

 }

 Output:

 Token 1: A

 Token 2: Quick

 Token 3: Brown

 Token 4: Fox

 Token 5: Jumps

 Token 6: over

 Token 7: the

 Token 8: lazy

 Token 9: dog

Note: Buffer allocated by strdup should be released with free(). strtok(), strrev() etc are some utility functions modify its input buffer and produce the result. This is why we should not pass a constant string. CPU will produce a access violation while execution. strdup() is usedful for these cases.

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