size_t(3type)                                                    size_t(3type)

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 at 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).

STANDARDS
       size_t C11, POSIX.1-2008.

       ssize_t
              POSIX.1-2008.

HISTORY
       size_t C89, POSIX.1-2001.

       ssize_t
              POSIX.1-2001.

       <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.

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

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)

Linux man-pages 6.7               2023-10-31                     size_t(3type)