This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding Linux
manual page for details of Linux behavior), or the interface may not be
implemented on Linux.
sys/types.h — data types
header shall define at least the following types:
- Used for file block counts.
- Used for block sizes.
- Used for system times in clock ticks or CLOCKS_PER_SEC; see
- Used for clock ID type in the clock and timer
- Used for device IDs.
- Used for file system block counts.
- Used for file system file counts.
- Used for group IDs.
- Used as a general identifier; can be used to contain at
least a pid_t, uid_t, or gid_t.
- Used for file serial numbers.
- Used for XSI interprocess communication.
- Used for some file attributes.
- Used for link counts.
- Used for file sizes.
- Used for process IDs and process group IDs.
- Used to identify a thread attribute object.
- Used to identify a barrier.
- Used to define a barrier attributes object.
- Used for condition variables.
- Used to identify a condition attribute object.
- Used for thread-specific data keys.
- Used for mutexes.
- Used to identify a mutex attribute object.
- Used for dynamic package initialization.
- Used for read-write locks.
- Used for read-write lock attributes.
- Used to identify a spin lock.
- Used to identify a thread.
- Used for sizes of objects.
- Used for a count of bytes or an error indication.
- Used for time in microseconds.
- Used for time in seconds.
- Used for timer ID returned by timer_create().
- Used to identify a trace stream attributes object
- Used to identify a trace event type.
- Used to identify a trace event type set.
- Used to identify a trace stream.
- Used for user IDs.
All of the types shall be defined as arithmetic types of an appropriate length,
with the following exceptions:
- mode_t shall be an integer type.
- dev_t shall be an integer type.
- nlink_t, uid_t, gid_t, and id_t
shall be integer types.
- blkcnt_t and off_t shall be signed integer
- fsblkcnt_t, fsfilcnt_t, and ino_t
shall be defined as unsigned integer types.
- size_t shall be an unsigned integer type.
- blksize_t, pid_t, and ssize_t shall be
signed integer types.
- clock_t shall be an integer or real-floating type.
time_t shall be an integer type.
The type ssize_t
shall be capable of storing values at least in the range
The type suseconds_t
shall be a signed integer type capable of storing
values at least in the range [−1, 1000000].
The implementation shall support one or more programming environments in which
the widths of blksize_t
are no greater than the width of type long
names of these programming environments can be obtained using the
() function or the getconf
There are no defined comparison or assignment operators for the following types:
The following sections are informative.
The System Interfaces volume of POSIX.1‐2008, confstr()
The Shell and Utilities volume of POSIX.1‐2008, getconf
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
7, Copyright (C) 2013 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013
Technical Corrigendum 1 applied.) In the event of any discrepancy between this
version and the original IEEE and The Open Group Standard, the original IEEE
and The Open Group Standard is the referee document. The original Standard can
be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are most likely
to have been introduced during the conversion of the source files to man page
format. To report such errors, see