strstr(3) Library Functions Manual strstr(3) strstr, strcasestr - (libc -lc) #include char *strstr(const char *haystack, const char *needle); #define _GNU_SOURCE /* feature_test_macros(7) */ #include char *strcasestr(const char *haystack, const char *needle); strstr() needle haystack. ('\0'). memmem(haystack, strlen(haystack), needle, strlen(needle)) strcasestr() strstr() . NULL . needle haystack . attributes(7). +----------------------+------------------------------------+---------------------------------------------------------------------------------------------+ | | | | +----------------------+------------------------------------+---------------------------------------------------------------------------------------------+ |strstr() | | MT-Safe | +----------------------+------------------------------------+---------------------------------------------------------------------------------------------+ |strcasestr() | | (locale) (MT-Safe) | +----------------------+------------------------------------+---------------------------------------------------------------------------------------------+ strstr() C11, POSIX.1-2008. strcasestr() GNU. strstr() POSIX.1-2001 C89. strcasestr() GNU. memchr(3), memmem(3), strcasecmp(3), strchr(3), string(3), strpbrk(3), strsep(3), strspn(3), strtok(3), wcsstr(3) 3 . . : . 6.18 25 2026 strstr(3)