The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition

### 2.12 Data Types

All of the data types used by various functions are defined by the implementation. The following table describes some of these types. Other types referenced in the description of a function, not mentioned here, can be found in the appropriate header for that function.

Defined Type | Description
--- | ---
cc_t | Type used for terminal special characters.
clock_t | Integer or real-floating type used for processor times, as defined in the ISO C standard.
clockid_t | Used for clock ID type in some timer functions.
dev_t | Arithmetic type used for device numbers.
DIR | Type representing a directory stream.
div_t | Structure type returned by the div() function.
FILE | Structure containing information about a file.
glob_t | Structure type used in pathname pattern matching.
fpos_t | Type containing all information needed to specify uniquely every position within a file.
gid_t | Integer type used for group IDs.
iconv_t | Type used for conversion descriptors.
id_t | Integer type used as a general identifier; can be used to contain at least the largest of a pid_t, uid_t, or gid_t.
ino_t | Unsigned integer type used for file serial numbers.
key_t | Arithmetic type used for XSI interprocess communication.
ldiv_t | Structure type returned by the ldiv() function.
mode_t | Integer type used for file attributes.
mqd_t | Used for message queue descriptors.
nfds_t | Integer type used for the number of file descriptors.
nlink_t | Integer type used for link counts.
off_t | Signed integer type used for file sizes.
pid_t | Signed integer type used for process and process group IDs.
pthread_attr_t | Used to identify a thread attribute object.
pthread_cond_t | Used for condition variables.
pthread_condattr_t | Used to identify a condition attribute object.
pthread_key_t | Used for thread-specific data keys.
pthread_mutex_t | Used for mutexes.
pthread_mutexattr_t | Used to identify a mutex attribute object.
pthread_once_t | Used for dynamic package initialization.
pthread_rwlock_t | Used for read-write locks.
pthread_rwlockattr_t | Used for read-write lock attributes.
pthread_t | Used to identify a thread.
ptrdiff_t | Signed integer type of the result of subtracting two pointers.
regex_t | Structure type used in regular expression matching.
regmatch_t | Structure type used in regular expression matching.
rlim_t | Unsigned integer type used for limit values, to which objects of type int and off_t can be cast without loss of value.
sem_t | Type used in performing semaphore operations.
sig_atomic_t | Integer type of an object that can be accessed as an atomic entity, even in the presence of asynchronous interrupts.
sigset_t | Integer or structure type of an object used to represent sets of signals.
size_t | Unsigned integer type used for size of objects.
speed_t | Type used for terminal baud rates.
ssize_t | Signed integer type used for a count of bytes or an error indication.
suseconds_t | Signed integer type used for time in microseconds.
tcflag_t | Type used for terminal modes.
time_t | Integer or real-floating type used for time in seconds, as defined in the ISO C standard.
timer_t | Used for timer ID returned by the timer_create() function.
uid_t | Integer type used for user IDs.
useconds_t | Unsigned integer type used for time in microseconds.
va_list | Type used for traversing variable argument lists.
wchar_t | Integer type whose range of values can represent distinct codes for all members of the largest extended character set specified by the supported locales
wctype_t | Scalar type which represents a character class descriptor.
wint_t | Integer type capable of storing any valid value of wchar_t or WEOF.
wordexp_t | Structure type used in word expansion.

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