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 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(): 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, and so performs an optimized search for c (i.e.,  no  use  of  a
       count  argument  to limit the range of the search).  If an instance of c is not found, the
       results are unpredictable.  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.

ATTRIBUTES

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

       ┌───────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                                      │ Attribute     │ Value   │
       ├───────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │memchr(), memrchr(), rawmemchr()                               │ Thread safety │ MT-Safe │
       └───────────────────────────────────────────────────────────────┴───────────────┴─────────┘

CONFORMING TO

       memchr(): POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.

       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

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

COLOPHON

       This page is part of release 5.13 of the Linux man-pages project.  A  description  of  the
       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at https://www.kernel.org/doc/man-pages/.

                                            2021-03-22                                  MEMCHR(3)