index

Name

index, rindex
- locate character in string

Library

libc.lib

Synopsis

#include <strings.h>

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

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

Return values

The functions index and rindex return a pointer to the located character, or NULL if the character does not appear in the string.

Detailed description

The index function locates the first occurrence of c (converted to a char ) in the string pointed to by s. The terminating null character is considered part of the string; therefore if c is ‘\0,’ the functions locate the terminating ‘\0.’

The rindex function is identical to index, except it locates the last occurrence of c.

Examples

#include <string.h>
#include <stdio.h>
int main()
{
    char one[50];
    char* ret;
    strcpy(one,"abcd");
    ret = index(one, ’c’);
    if(!strncmp(one+2,ret,1)) printf("index of \ ’c\ ’ in string \"abcd\" is %d \n",2);
    ret = index(one, ’z’);
    if(ret == NULL) printf("\ ’z\ ’ not found in string \"abcd\"\n");
    ret = index(one, ’\0’);
    if(!strncmp(one+4,ret,1)) printf("index of \ ’\ \0\ ’ in string \"abcd\" is %d\n",4);
    strcpy(one,"cdcab");
    ret = rindex(one, ’c’);
    if(!strncmp(one+2,ret,1)) printf("rindex of \ ’c\ ’ in string \"cscab\" is %d\n",2);
    strcpy(one,"dcab");
    ret = rindex(one, ’\0’);
    if(!strncmp(one+4,ret,1)) printf("index of \ ’\ \0\ ’ in string \"dcab\" is %d\n",4);
    return 0;
}

Output

index of ’c’ in string "abcd" is 2
 ’z’ not found in string "abcd"
index of ’\0’ in string "abcd" is 4
rindex of ’c’ in string "cscab" is 2
index of ’\0’ in string "dcab" is 4

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