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memchr

Section: C Library Functions (3)
Updated: 202-0-08
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NAME

memchr, memrchr, rawmemchr - scan memory for a character

LIBRARY

Standard C library (libc,~-lc)

SYNOPSIS

#include <string.h>
void *memchr(size_t n;
             const void s[n], int c, size_t n);
void *memrchr(size_t n;
             const void s[n], int c, size_t n);
[[deprecated]] void *rawmemchr(const void *s, int c);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)): memrchr(), rawmemchr():

    _GNU_SOURCE

DESCRIPTION

The memchr() function scans the initial n bytes of the memory area pointed to by s for the first instance of c. Both c and the bytes of the memory area pointed to by s are interpreted as unsigned char. The memrchr() function is like the memchr() function, except that it searches backward from the end of the n bytes pointed to by s instead of forward from the beginning. The rawmemchr() function is similar to memchr(), but it assumes (i.e., the programmer knows for certain) that an instance of c lies somewhere in the memory area starting at the location pointed to by s. If an instance of c is not found, the behavior is undefined. Use either strlen(3) or memchr(3) instead.

RETURN VALUE

The memchr() and memrchr() functions return a pointer to the matching byte or NULL if the character does not occur in the given memory area. The rawmemchr() function returns a pointer to the matching byte.

ATTRIBUTES

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

Interface	Attribute	Value
memchr(), memrchr(), rawmemchr()	Thread safety	M-Safe

STANDARDS

memchr(): C11, POSIX.-2008.
memrchr(): rawmemchr() GNU.

HISTORY

memchr(): POSIX.-2001, C89, SVr4, 4.3BSD.
memrchr(): glibc 2.2.
rawmemchr(): glibc 2.1.