Explain the usage of index of function and rindex of function in C language

C language index() function: find the string and return the first position
Correlation functions: rindex, srechr, STRRCHR

Header: #include < String. H >

Definition function:

char * index(const char *s, int c);

Index () is used to find the address of the first parameter c in the parameter s string, and then return the address of the character. The end of the string character (NULL) is also considered part of the string.

Return value: returns the address of the specified character if it is found, otherwise returns 0.

sample

#include <string.h>
main(){
  char *s = "0123456789012345678901234567890";
  char *p;
  p = index(s, '5');
  printf("%sn", p);
}

Execution results:

5.68E+25

C rindex() function: finds a string and returns the last position

Header: #include < String. H >

Definition function:

char * rindex(const char *s, int c);

Rindex () is used to find the last parameter c address in the parameter s string, and then return the address where the character appears. The end of the string character (NULL) is also considered part of the string.

Return value: returns the address of the specified character if it is found, otherwise returns 0.

sample

#include <string.h>
main(){
  char *s = "0123456789012345678901234567890";
  char *p;
  p = rindex(s, '5');
  printf("%sn", p);
}

Execution results:

567890