Is there a built in function to get the back half of a strsep()?

Question

In short, currently the code below outputs: The substring is AES. Unfortunately, I'm looking to get the result The substring is 100. This is due to the fact that strsep() keeps only the first portion of the split, and not the second. Is there a way to make the 2nd portion the one that's kept instead?

#include <stdio.h>
#include <string.h>

int main () {
   const char haystack[50] = "SHA1 = 99\nAES = 100";
   const char needle[10] = "Point";
   char *ret;
   char *bonus;
   ret = strstr(haystack, "AES");

   bonus = strsep(&ret, "=");

   printf("The substring is: %s\n", bonus);

   return(0);
}

print `ret` instead of `bonus`: `printf("The substring is: %s\n", ret);` — isrnick, Jun 03 '20 at 01:18
The documentation is very clear how it works: https://www.man7.org/linux/man-pages/man3/strsep.3.html — jwdonahue, Jun 03 '20 at 01:24
This is meant to make it convenient to write a loop to process multiple fields separated by a delimiter. `while ((f = strsep(&ret, ",")) != NULL) process_field(f);` — Nate Eldredge, Jun 03 '20 at 02:17

isrnick · Accepted Answer · 2020-06-03T05:31:14.267

From strsep function's documentation :

char *strsep(char **stringp, const char *delim);
If *stringp is NULL, the strsep() function returns NULL and does nothing else. Otherwise, this function finds the first token in the string *stringp, that is delimited by one of the bytes in the string delim. This token is terminated by overwriting the delimiter with a null byte ('\0'), and *stringp is updated to point past the token. In case no delimiter was found, the token is taken to be the entire string *stringp, and *stringp is made NULL.

So in your program's case you should print ret instead of bonus:

bonus = strsep(&ret, "=");

printf("The substring is: %s\n", ret);

Since ret will point past the token "=".

Is there a built in function to get the back half of a strsep()?

1 Answers1