strcasestr()

Updated: April 19, 2023

Find one string inside another, ignoring case

Synopsis:

#include <string.h>

char* strcasestr( char* str,
                  char* substr );

Arguments:

str
The string that you want to search.
substr
The string that you're looking for.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The strcasestr() function locates the first occurrence in the string pointed to by str of the sequence of characters (excluding the terminating null character) in the string pointed to by substr, ignoring the case of both arguments. If substr is an empty string, the function returns str.

The POSIX strstr() function is similar, but it considers the case of both arguments.

Returns:

A pointer to the located string, or NULL if the string isn't found.

Examples:

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

int main( void )
  {
    printf( "%s\n", strcasestr("This IS an example", "Is") );
    return EXIT_SUCCESS;
  }

produces the output:

is IS an example

Classification:

Unix

Safety:  
Cancellation point No
Interrupt handler Yes
Signal handler Yes
Thread Yes