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() op-
erator. It is an unsigned integer type capable of storing val-
ues 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 func-
tions, which is z; resulting commonly in %zd or %zi for printing
ssize_t values. Although z works for ssize_t on most implemen-
tations, portable POSIX programs should avoid using it—for exam-
ple, 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>, <mone-
tary.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 6.03 2023-02-05 size_t(3type)
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