MEMMEM Section: Linux Programmer's Manual (3) Updated: January 13, 2025 Index   NAME memmem - locate a substring   SYNOPSIS #include <string.h> void *memmem(const void *haystack, size_t haystacklen, const void *needle, size_t needlelen);   DESCRIPTION The memmem() function finds the start of the first occurrence of the substring needle of length needlelen in the memory area haystack of length haystacklen.   RETURN VALUE The memmem() function returns a pointer to the beginning of the substring, or NULL if the substring is not found.   CONFORMING TO This function is a GNU extension.   BUGS This function was broken in Linux libraries up to and including libc 5.0.9; there the `needle' and `haystack' arguments were interchanged, and a pointer to the end of the first occurrence of needle was returned. Since libc 5.0.9 is still widely used, this is a dangerous function to use. Both old and new libc's have the bug that if needle is empty haystack-1 (instead of haystack) is returned. And glibc (2.0.5) makes it worse, and returns a pointer to the last byte of `haystack'. Hopefully this will be fixed. For the time being, memmem() should not be used with an empty `needle'.   SEE ALSO   Index NAME SYNOPSIS DESCRIPTION RETURN VALUE CONFORMING TO BUGS SEE ALSO This document was created by using the manual pages. Time: 11:58:05 GMT, March 24, 2025