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MEMCHR

Section: Linux Programmer's Manual (3)
Updated: 2009-12-04
Index Return to Main Contents

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NAME

memchr, memrchr, rawmemchr - scan memory for a character  

SYNOPSIS

#include <string.h>

void *memchr(const void *s, int c, size_t n);

void *memrchr(const void *s, int c, size_t n);

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 first n bytes of the memory area pointed to by s for the character c. The first byte to match c (interpreted as an unsigned character) stops the operation.

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(): it assumes (i.e., the programmer knows for certain) that the character c lies somewhere in the string s, and so performs an optimized search for the character c (i.e., no checking for the terminating null byte, or use of an argument, n, to limit the range of the search). If the character c is not in the string s, then rawmemchr() may proceed to search beyond the end of the string, and the result is unspecified. The following call is a fast means of locating a string's terminating null byte:

char *p = rawmemchr(s, '\0');

 

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, if one is found. If no matching byte is found, the result is unspecified.  

VERSIONS

rawmemchr() first appeared in glibc in version 2.1.

memrchr() first appeared in glibc in version 2.2.  

CONFORMING TO

The memchr() function conforms to SVr4, 4.3BSD, C89, C99, POSIX.1-2001.

The memrchr() function is a GNU extension, available since glibc 2.1.91.

The rawmemchr() function is a GNU extension, available since glibc 2.1.  

SEE ALSO

ffs(3), index(3), rindex(3), strchr(3), strpbrk(3), strrchr(3), strsep(3), strspn(3), strstr(3), wmemchr(3)  

COLOPHON

This page is part of release 3.35 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://man7.org/linux/man-pages/.

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Index

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

VERSIONS

CONFORMING TO

SEE ALSO

COLOPHON

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