strcasestr(3)              Library Functions Manual              strcasestr(3)

NAME
       strcasestr - string case-insensitive search substring

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #define _GNU_SOURCE  // See feature_test_macros(7)
       #include <string.h>

       char *strcasestr(const char *haystack, const char *needle);

DESCRIPTION
       strcasestr() is like strstr(), but ignores the case of both arguments.

RETURN VALUE
       See strstr(3).

ATTRIBUTES
       For an explanation of the terms used in this section, see
       attributes(7).

       +-------------------------------------+---------------+----------------+
       |Interface                            | Attribute     | Value          |
       +-------------------------------------+---------------+----------------+
       |strcasestr ()                        | Thread safety | MT-Safe locale |
       +-------------------------------------+---------------+----------------+
STANDARDS
       GNU.

HISTORY
       GNU.

SEE ALSO
       string(3), strstr(3)

Linux man-pages 6.19              2026-05-16                     strcasestr(3)