NAME

       size_t, ssize_t - count of bytes

LIBRARY

       Standard C library (libc)

SYNOPSIS

       #include <stddef.h>

       typedef /* ... */  size_t;

       #include <sys/types.h>

       typedef /* ... */  ssize_t;

DESCRIPTION

       size_t Used  for  a  count of bytes.  It is the result of the sizeof() operator.  It is an
              unsigned integer type capable of storing values in the range [0, SIZE_MAX].

       ssize_t
              Used for a count of bytes or an error indication.  It  is  a  signed  integer  type
              capable of storing values al least in the range [-1, SSIZE_MAX].

   Use with printf(3) and scanf(3)
       size_t The  length  modifier  for  size_t  for  the printf(3) and the scanf(3) families of
              functions is z, resulting commonly in %zu or %zx for printing size_t values.

       ssize_t
              glibc and most other implementations provide a length modifier for ssize_t for  the
              printf(3) and the scanf(3) families of functions, which is z; resulting commonly in
              %zd or %zi for printing ssize_t values.  Although  z  works  for  ssize_t  on  most
              implementations,  portable  POSIX  programs  should  avoid using it—for example, by
              converting the value to intmax_t and using its length modifier (j).

VERSIONS

       size_t <aio.h>,  <glob.h>,  <grp.h>,  <iconv.h>,  <mqueue.h>,  <pwd.h>,  <signal.h>,   and
              <sys/socket.h> define size_t since POSIX.1-2008.

       ssize_t
              <aio.h>, <mqueue.h>, and <sys/socket.h> define ssize_t since POSIX.1-2008.

STANDARDS

       size_t: C99 and later; POSIX.1-2001 and later.
       ssize_t: POSIX.1-2001 and later.

NOTES

       size_t The  following  headers also provide size_t: <aio.h>, <glob.h>, <grp.h>, <iconv.h>,
              <monetary.h>, <mqueue.h>, <ndbm.h>,  <pwd.h>,  <regex.h>,  <search.h>,  <signal.h>,
              <stdio.h>,   <stdlib.h>,   <string.h>,   <strings.h>,   <sys/mman.h>,  <sys/msg.h>,
              <sys/sem.h>, <sys/shm.h>,  <sys/socket.h>,  <sys/types.h>,  <sys/uio.h>,  <time.h>,
              <unistd.h>, <wchar.h>, and <wordexp.h>.

       ssize_t
              The  following  headers  also  provide  ssize_t: <aio.h>, <monetary.h>, <mqueue.h>,
              <stdio.h>, <sys/msg.h>, <sys/socket.h>, <sys/uio.h>, and <unistd.h>.

SEE ALSO

       read(2),  readlink(2),  readv(2),  recv(2),  send(2),   write(2),   fread(3),   fwrite(3),
       memcmp(3), memcpy(3), memset(3), offsetof(3), ptrdiff_t(3type)