The following standards-compliant system data types are defined:
blkcnt_t
file block counts
clock_t
system clock ticks
fsblkcnt_t
file system block counts
-
fsfilcnt_t
file system file counts
-
ino_t
file serial numbers
key_t
interprocess communication
pid_t
process and process group IDs
useconds_t
time in microseconds
In addition, when included in user applications,
<sys/types.h> includes
<pthread.h>, and thus it defines also the types used in the POSIX Threads Library,
pthread(3).
Each described type may vary across machines and operating systems. Only the following properties are guaranteed by the IEEE Std 1003.1-2001 (“POSIX.1”) standard:
1.
The type ssize_t is capable of storing integer values at least in the range [-1, SSIZE_MAX].
2.
The type useconds_t is an unsigned integer capable of storing values at least in the range [0, 1000000].
3.
The type suseconds_t is a signed integer capable of storing values at least in the range [-1, 1000000].
4.
The time_t and clock_t types are either integers or real-floating types.
5.
The following types are integers: gid_t, id_t, mode_t, nlink_t, and uid_t.
6.
The following types are signed integers: blkcnt_t, blksize_t, off_t, pid_t, and ssize_t.
7.
The following types are unsigned integers: fsblkcnt_t, fsfilcnt_t, ino_t, and size_t.