memchr(3)

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

   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 4.09 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/.

                              2015-08-08                         MEMCHR(3)

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