mirror of https://github.com/mkerrisk/man-pages
918 lines
18 KiB
Groff
918 lines
18 KiB
Groff
.\" Copyright (c) 2020 by Alejandro Colomar <colomar.6.4.3@gmail.com>
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.\" and Copyright (c) 2020 by Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.\"
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.TH SYSTEM_DATA_TYPES 7 2020-09-13 "Linux" "Linux Programmer's Manual"
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.SH NAME
|
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system_data_types \- overview of system data types
|
|
.SH DESCRIPTION
|
|
.\" Layout:
|
|
.\" A list of type names (the struct/union keyword will be omitted).
|
|
.\" Each entry will have the following parts:
|
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.\" * Include
|
|
.\" The headers will be in the following order:
|
|
.\" 1) The main header that shall define the type
|
|
.\" according to the C Standard,
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.\" and
|
|
.\" the main header that shall define the type
|
|
.\" according to POSIX,
|
|
.\" in alphabetical order.
|
|
.\" ;
|
|
.\" 2) All other headers that shall define the type
|
|
.\" as described in the previous header(s)
|
|
.\" according to the C Standard or POSIX,
|
|
.\" in alphabetical order.
|
|
.\" *) All headers that define the type
|
|
.\" *if* the type is not defined by C nor POSIX,
|
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.\" in alphabetical order.
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|
.\"
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|
.\" * Definition (no "Definition" header)
|
|
.\" Only struct/union types will have definition;
|
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.\" typedefs will remain opaque.
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.\"
|
|
.\" * Description (no "Description" header)
|
|
.\" A few lines describing the type.
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|
.\"
|
|
.\" * Conforming to
|
|
.\" Format: CXY and later; POSIX.1-XXXX and later.
|
|
.\" Forget about pre-C99 C standards (i.e., C89/C90)
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|
.\"
|
|
.\" * Notes (optional)
|
|
.\"
|
|
.\" * See also
|
|
.\"------------------------------------- aiocb ------------------------/
|
|
.TP
|
|
.I aiocb
|
|
.IP
|
|
Include:
|
|
.IR <aio.h> .
|
|
.IP
|
|
.EX
|
|
struct aiocb {
|
|
int aio_fildes; /* File descriptor */
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|
off_t aio_offset; /* File offset */
|
|
volatile void *aio_buf; /* Location of buffer */
|
|
size_t aio_nbytes; /* Length of transfer */
|
|
int aio_reqprio; /* Request priority offset */
|
|
struct sigevent aio_sigevent; /* Signal number and value */
|
|
int aio_lio_opcode;/* Operation to be performed */
|
|
};
|
|
.EE
|
|
.IP
|
|
For further information about this structure, see
|
|
.BR aio (7).
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR aio_cancel (3),
|
|
.BR aio_error (3),
|
|
.BR aio_fsync (3),
|
|
.BR aio_read (3),
|
|
.BR aio_return (3),
|
|
.BR aio_suspend (3),
|
|
.BR aio_write (3),
|
|
.BR lio_listio (3)
|
|
.\"------------------------------------- fenv_t -----------------------/
|
|
.TP
|
|
.I fenv_t
|
|
.IP
|
|
Include:
|
|
.IR <fenv.h> .
|
|
.IP
|
|
Represents the entire floating-point environment.
|
|
The floating-point environment refers collectively to
|
|
any floating-point status flags and
|
|
control modes supported by the implementation.
|
|
.IP
|
|
Conforming to: C99 and later; POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR fenv (3)
|
|
.\"------------------------------------- gid_t ----------------------/
|
|
.TP
|
|
.I gid_t
|
|
.IP
|
|
Include:
|
|
.IR <sys/types.h> ;
|
|
or
|
|
.I <grp.h>
|
|
or
|
|
.I <pwd.h>
|
|
or
|
|
.I <signal.h>
|
|
or
|
|
.I <stropts.h>
|
|
or
|
|
.I <sys/ipc.h>
|
|
or
|
|
.I <sys/stat.h>
|
|
or
|
|
.IR <unistd.h> .
|
|
.IP
|
|
A type used to hold group IDs.
|
|
According to POSIX,
|
|
this shall be an integer type.
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR chown (2),
|
|
.BR getgid (2),
|
|
.BR getegid (2),
|
|
.BR getgroups (2),
|
|
.BR getresgid (2),
|
|
.BR getgrnam (2),
|
|
.BR credentials (7)
|
|
.\"------------------------------------- id_t -------------------------/
|
|
.TP
|
|
.I id_t
|
|
.IP
|
|
Include:
|
|
.IR <sys/types.h> ;
|
|
or
|
|
.IR <sys/resource.h> .
|
|
.IP
|
|
A type used to hold a general identifier.
|
|
According to POSIX,
|
|
this shall be an integer type that can be used to contain a
|
|
.IR pid_ t ,
|
|
.IR uid_ t ,
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|
or
|
|
.IR gid_ t .
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR getpriority (2),
|
|
.BR waitid (2)
|
|
.\"------------------------------------- pid_t ------------------------/
|
|
.TP
|
|
.I pid_t
|
|
.IP
|
|
Include
|
|
.IR <sys/types.h> ;
|
|
or
|
|
.I <fcntl.h>
|
|
or
|
|
.I <sched.h>
|
|
or
|
|
.I <signal.h>
|
|
or
|
|
.I <spawn.h>
|
|
or
|
|
.I <sys/msg.h>
|
|
or
|
|
.I <sys/sem.h>
|
|
or
|
|
.I <sys/shm.h>
|
|
or
|
|
.I <sys/wait.h>
|
|
or
|
|
.I <termios.h>
|
|
or
|
|
.I <time.h>
|
|
or
|
|
.I <unistd.h>
|
|
or
|
|
.IR <utmpx.h> .
|
|
.IP
|
|
This type is used for storing process IDs, process group IDs, and session IDs.
|
|
According to POSIX, it shall be a signed integer type,
|
|
and the implementation shall support one or more programming environments
|
|
where the width of
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|
.I pid_t
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|
is no greater than the width of the type
|
|
.IR long .
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR fork (2),
|
|
.BR getpid (2),
|
|
.BR getppid (2),
|
|
.BR getsid (2),
|
|
.BR gettid (2),
|
|
.BR getpgid (2),
|
|
.BR kill (2),
|
|
.BR pidfd_open (2),
|
|
.BR sched_setscheduler (2),
|
|
.BR waitpid (2),
|
|
.BR sigqueue (3),
|
|
.BR credentials (7),
|
|
.\"------------------------------------- ptrdiff_t --------------------/
|
|
.TP
|
|
.I ptrdiff_t
|
|
.IP
|
|
Include:
|
|
.IR <stddef.h> .
|
|
.IP
|
|
Used for a count of elements, and array indices.
|
|
It is the result of subtracting two pointers.
|
|
According to the C language standard, it shall be a signed integer type
|
|
capable of storing values in the range
|
|
.BR "" [ PTRDIFF_MIN ,
|
|
.BR PTRDIFF_MAX ].
|
|
.IP
|
|
The length modifier for
|
|
.I ptrdiff_t
|
|
for the
|
|
.BR printf (3)
|
|
and the
|
|
.BR scanf (3)
|
|
families of functions is
|
|
.BR t ;
|
|
resulting commonly in
|
|
.B %td
|
|
or
|
|
.B %ti
|
|
for printing
|
|
.I ptrdiff_t
|
|
values.
|
|
.IP
|
|
Conforming to: C99 and later; POSIX.1-2001 and later.
|
|
.IP
|
|
See also the
|
|
.I size_t
|
|
and
|
|
.I ssize_t
|
|
types in this page.
|
|
.\"------------------------------------- regmatch_t -------------------/
|
|
.TP
|
|
.I regmatch_t
|
|
.IP
|
|
Include:
|
|
.IR <regex.h> .
|
|
.IP
|
|
.EX
|
|
typedef struct {
|
|
regoff_t rm_so; /* Byte offset from start of string
|
|
to start of substring */
|
|
regoff_t rm_eo; /* Byte offset from start of string of
|
|
the first character after the end of
|
|
substring */
|
|
} regmatch_t;
|
|
.EE
|
|
.IP
|
|
This is a structure type used in regular expression matching.
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR regexec (3)
|
|
.\"------------------------------------- regoff_t ---------------------/
|
|
.TP
|
|
.I regoff_t
|
|
.IP
|
|
Include:
|
|
.IR <regex.h> .
|
|
.IP
|
|
According to POSIX, it shall be a signed integer type
|
|
capable of storing the largest value that can be stored in either a
|
|
.I ptrdiff_t
|
|
type or a
|
|
.I ssize_t
|
|
type.
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
Notes: Prior to POSIX.1-2008, the type was capable of storing
|
|
the largest value that can be stored in either an
|
|
.I off_t
|
|
type or a
|
|
.I ssize_t
|
|
type.
|
|
.IP
|
|
See also the
|
|
.I regmatch_t
|
|
structure and the
|
|
.I ptrdiff_t
|
|
and
|
|
.I ssize_t
|
|
types in this page.
|
|
.\"------------------------------------- sigevent ---------------------/
|
|
.TP
|
|
.I sigevent
|
|
.IP
|
|
Include:
|
|
.IR <signal.h> ;
|
|
or
|
|
.I <aio.h>
|
|
or
|
|
.I <mqueue.h>
|
|
or
|
|
.IR <time.h> .
|
|
.IP
|
|
.EX
|
|
struct sigevent {
|
|
int sigev_notify; /* Notification type */
|
|
int sigev_signo; /* Signal number */
|
|
union sigval sigev_value; /* Signal value */
|
|
void (*sigev_notify_function)(union sigval);
|
|
/* Notification function */
|
|
pthread_attr_t *sigev_notify_attributes;
|
|
/* Notification attributes */
|
|
};
|
|
.EE
|
|
.IP
|
|
For further details about this type, see
|
|
.BR sigevent (7).
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
Notes:
|
|
.I <aio.h>
|
|
and
|
|
.I <time.h>
|
|
define
|
|
.I sigevent
|
|
since POSIX.1-2008.
|
|
.IP
|
|
See also:
|
|
.BR timer_create (2),
|
|
.BR getaddrinfo_a (3),
|
|
.BR lio_listio (3),
|
|
.BR mq_notify (3)
|
|
.IP
|
|
See also the
|
|
.I aiocb
|
|
structure in this page.
|
|
.\"------------------------------------- siginfo_t --------------------/
|
|
.TP
|
|
.I siginfo_t
|
|
.IP
|
|
Include:
|
|
.IR <signal.h> ;
|
|
or
|
|
.IR <sys/wait.h> .
|
|
.IP
|
|
.EX
|
|
typedef struct {
|
|
int si_signo; /* Signal number */
|
|
int si_code; /* Signal code */
|
|
pid_t si_pid; /* Sending process ID */
|
|
uid_t si_uid; /* Real user ID of sending process */
|
|
void *si_addr; /* Address of faulting instruction */
|
|
int si_status; /* Exit value or signal */
|
|
union sigval si_value; /* Signal value */
|
|
} siginfo_t;
|
|
.EE
|
|
.IP
|
|
Information associated with a signal.
|
|
For further details on this structure
|
|
(including additional, Linux-specific fields), see
|
|
.BR sigaction (2).
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR pidfd_send_signal (2),
|
|
.BR rt_sigqueueinfo (2),
|
|
.BR sigaction (2),
|
|
.BR sigwaitinfo (2),
|
|
.BR psiginfo (3)
|
|
.\"------------------------------------- sigset_t ---------------------/
|
|
.TP
|
|
.I sigset_t
|
|
.IP
|
|
Include:
|
|
.IR <signal.h> ;
|
|
or
|
|
.I <spawn.h>
|
|
or
|
|
.IR <sys/select.h> .
|
|
.IP
|
|
This is a type that represents a set of signals.
|
|
According to POSIX, this shall be an integer or structure type.
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR epoll_pwait (2),
|
|
.BR ppoll (2),
|
|
.BR pselect (2),
|
|
.BR sigaction (2),
|
|
.BR signalfd (2),
|
|
.BR sigpending (2),
|
|
.BR sigprocmask (2),
|
|
.BR sigsuspend (2),
|
|
.BR sigwaitinfo (2),
|
|
.BR signal (7)
|
|
.\"------------------------------------- sigval -----------------------/
|
|
.TP
|
|
.I sigval
|
|
.IP
|
|
Include:
|
|
.IR <signal.h> .
|
|
.IP
|
|
.EX
|
|
union sigval {
|
|
int sigval_int; /* Integer value */
|
|
void *sigval_ptr; /* Pointer value */
|
|
};
|
|
.EE
|
|
.IP
|
|
Data passed with a signal.
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR pthread_sigqueue (3),
|
|
.BR sigqueue (3),
|
|
.BR sigevent (7)
|
|
.IP
|
|
See also the
|
|
.I sigevent
|
|
structure
|
|
and the
|
|
.I siginfo_t
|
|
type
|
|
in this page.
|
|
.\"------------------------------------- size_t -----------------------/
|
|
.TP
|
|
.I size_t
|
|
.IP
|
|
Include:
|
|
.I <stddef.h>
|
|
or
|
|
.IR <sys/types.h> ;
|
|
or
|
|
.I <aio.h>
|
|
or
|
|
.I <glob.h>
|
|
or
|
|
.I <grp.h>
|
|
or
|
|
.I <iconv.h>
|
|
or
|
|
.I <monetary.h>
|
|
or
|
|
.I <mqueue.h>
|
|
or
|
|
.I <ndbm.h>
|
|
or
|
|
.I <pwd.h>
|
|
or
|
|
.I <regex.h>
|
|
or
|
|
.I <search.h>
|
|
or
|
|
.I <signal.h>
|
|
or
|
|
.I <stdio.h>
|
|
or
|
|
.I <stdlib.h>
|
|
or
|
|
.I <string.h>
|
|
or
|
|
.I <strings.h>
|
|
or
|
|
.I <sys/mman.h>
|
|
or
|
|
.I <sys/msg.h>
|
|
or
|
|
.I <sys/sem.h>
|
|
or
|
|
.I <sys/shm.h>
|
|
or
|
|
.I <sys/socket.h>
|
|
or
|
|
.I <sys/uio.h>
|
|
or
|
|
.I <time.h>
|
|
or
|
|
.I <unistd.h>
|
|
or
|
|
.I <wchar.h>
|
|
or
|
|
.IR <wordexp.h> .
|
|
.IP
|
|
Used for a count of bytes. It is the result of the
|
|
.I sizeof
|
|
operator.
|
|
According to the C language standard,
|
|
it shall be an unsigned integer type
|
|
capable of storing values in the range [0,
|
|
.BR SIZE_MAX ].
|
|
According to POSIX,
|
|
the implementation shall support one or more programming environments
|
|
where the width of
|
|
.I size_t
|
|
is no greater than the width of the type
|
|
.IR long .
|
|
.IP
|
|
The length modifier for
|
|
.I size_t
|
|
for the
|
|
.BR printf (3)
|
|
and the
|
|
.BR scanf (3)
|
|
families of functions is
|
|
.BR z ;
|
|
resulting commonly in
|
|
.B %zu
|
|
or
|
|
.B %zx
|
|
for printing
|
|
.I size_t
|
|
values.
|
|
.IP
|
|
Conforming to: C99 and later; POSIX.1-2001 and later.
|
|
.IP
|
|
Notes:
|
|
.IR <aio.h> ,
|
|
.IR <glob.h> ,
|
|
.IR <grp.h> ,
|
|
.IR <iconv.h> ,
|
|
.IR <mqueue.h> ,
|
|
.IR <pwd.h> ,
|
|
.I <signal.h>
|
|
and
|
|
.I <sys/socket.h>
|
|
define
|
|
.I size_t
|
|
since POSIX.1-2008.
|
|
.IP
|
|
See also:
|
|
.BR read (2),
|
|
.BR write (2),
|
|
.BR memcmp (3),
|
|
.BR fread (3),
|
|
.BR fwrite (3),
|
|
.BR memcmp (3),
|
|
.BR memcpy (3),
|
|
.BR memset (3),
|
|
.BR offsetof (3)
|
|
.IP
|
|
See also the
|
|
.I ptrdiff_t
|
|
and
|
|
.I ssize_t
|
|
types in this page.
|
|
.\"------------------------------------- ssize_t ----------------------/
|
|
.TP
|
|
.I ssize_t
|
|
.IP
|
|
Include:
|
|
.IR <sys/types.h> ;
|
|
or
|
|
.I <aio.h>
|
|
or
|
|
.I <monetary.h>
|
|
or
|
|
.I <mqueue.h>
|
|
or
|
|
.I <stdio.h>
|
|
or
|
|
.I <sys/msg.h>
|
|
or
|
|
.I <sys/socket.h>
|
|
or
|
|
.I <sys/uio.h>
|
|
or
|
|
.IR <unistd.h> .
|
|
.IP
|
|
Used for a count of bytes or an error indication.
|
|
According to POSIX, it shall be a signed integer type
|
|
capable of storing values at least in the range [-1,
|
|
.BR SSIZE_MAX ],
|
|
and the implementation shall support one or more programming environments
|
|
where the width of
|
|
.I ssize_t
|
|
is no greater than the width of the type
|
|
.IR long .
|
|
.IP
|
|
Glibc and most other implementations provide a length modifier for
|
|
.I ssize_t
|
|
for the
|
|
.BR printf (3)
|
|
and the
|
|
.BR scanf (3)
|
|
families of functions, which is
|
|
.BR z ;
|
|
resulting commonly in
|
|
.B %zd
|
|
or
|
|
.B %zi
|
|
for printing
|
|
.I ssize_t
|
|
values.
|
|
Although
|
|
.B z
|
|
works for
|
|
.I ssize_t
|
|
on most implementations,
|
|
portable POSIX programs should avoid using it\(emfor example,
|
|
by converting the value to
|
|
.I intmax_t
|
|
and using its length modifier
|
|
.RB ( j ).
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR read (2),
|
|
.BR readlink (2),
|
|
.BR readv (2),
|
|
.BR recv (2),
|
|
.BR send (2),
|
|
.BR write (2)
|
|
.IP
|
|
See also the
|
|
.I ptrdiff_t
|
|
and
|
|
.I size_t
|
|
types in this page.
|
|
.\"------------------------------------- suseconds_t ------------------/
|
|
.TP
|
|
.I suseconds_t
|
|
.IP
|
|
Include:
|
|
.IR <sys/types.h> ;
|
|
or
|
|
.I <sys/select.h>
|
|
or
|
|
.IR <sys/time.h> .
|
|
.IP
|
|
Used for time in microseconds.
|
|
According to POSIX, it shall be a signed integer type
|
|
capable of storing values at least in the range [-1, 1000000],
|
|
and the implementation shall support one or more programming environments
|
|
where the width of
|
|
.I suseconds_t
|
|
is no greater than the width of the type
|
|
.IR long .
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
See also the
|
|
.I timeval
|
|
structure in this page.
|
|
.\"------------------------------------- time_t -----------------------/
|
|
.TP
|
|
.I time_t
|
|
.IP
|
|
Include:
|
|
.I <sys/types.h>
|
|
or
|
|
.IR <time.h> ;
|
|
or
|
|
.I <sched.h>
|
|
or
|
|
.I <sys/msg.h>
|
|
or
|
|
.I <sys/select.h>
|
|
or
|
|
.I <sys/sem.h>
|
|
or
|
|
.I <sys/shm.h>
|
|
or
|
|
.I <sys/stat.h>
|
|
or
|
|
.I <sys/time.h>
|
|
or
|
|
.IR <utime.h> .
|
|
.IP
|
|
Used for time in seconds.
|
|
According to POSIX, it shall be an integer type.
|
|
.IP
|
|
Conforming to: C99 and later; POSIX.1-2001 and later.
|
|
.IP
|
|
Notes:
|
|
.I <sched.h>
|
|
defines
|
|
.I time_t
|
|
since POSIX.1-2008.
|
|
.IP
|
|
See also:
|
|
.BR stime (2),
|
|
.BR time (2),
|
|
.BR ctime (3),
|
|
.BR difftime (3)
|
|
.\"------------------------------------- timer_t ----------------------/
|
|
.TP
|
|
.I timer_t
|
|
.IP
|
|
Include:
|
|
.IR <sys/types.h> ;
|
|
or
|
|
.IR <time.h> .
|
|
.IP
|
|
Used for timer ID returned by
|
|
.BR timer_create (2).
|
|
According to POSIX,
|
|
there are no defined comparison or assignment operators for this type.
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR timer_create (2),
|
|
.BR timer_delete (2),
|
|
.BR timer_getoverrun (2),
|
|
.BR timer_settime (2)
|
|
.\"------------------------------------- timespec ---------------------/
|
|
.TP
|
|
.I timespec
|
|
.IP
|
|
Include:
|
|
.IR <time.h> ;
|
|
or
|
|
.I <aio.h>
|
|
or
|
|
.I <mqueue.h>
|
|
or
|
|
.I <sched.h>
|
|
or
|
|
.I <signal.h>
|
|
or
|
|
.I <sys/select.h>
|
|
or
|
|
.IR <sys/stat.h> .
|
|
.IP
|
|
.EX
|
|
struct timespec {
|
|
time_t tv_sec; /* Seconds */
|
|
long tv_nsec; /* Nanoseconds */
|
|
};
|
|
.EE
|
|
.IP
|
|
Describes times in seconds and nanoseconds.
|
|
.IP
|
|
Conforming to: C11 and later; POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR clock_gettime (2),
|
|
.BR clock_nanosleep (2),
|
|
.BR nanosleep (2),
|
|
.BR timerfd_gettime (2),
|
|
.BR timer_gettime (2)
|
|
.\"------------------------------------- timeval ----------------------/
|
|
.TP
|
|
.I timeval
|
|
.IP
|
|
Include:
|
|
.IR <sys/time.h> ;
|
|
or
|
|
.I <sys/resource.h>
|
|
or
|
|
.I <sys/select.h>
|
|
or
|
|
.IR <utmpx.h> .
|
|
.IP
|
|
.EX
|
|
struct timeval {
|
|
time_t tv_sec; /* Seconds */
|
|
suseconds_t tv_usec; /* Microseconds */
|
|
};
|
|
.EE
|
|
.IP
|
|
Describes times in seconds and microseconds.
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR gettimeofday (2),
|
|
.BR select (2),
|
|
.BR utimes (2),
|
|
.BR adjtime (3),
|
|
.BR futimes (3),
|
|
.BR timeradd (3)
|
|
.\"------------------------------------- uid_t ----------------------/
|
|
.TP
|
|
.I uid_t
|
|
.IP
|
|
Include:
|
|
.IR <sys/types.h> ;
|
|
or
|
|
.I <pwd.h>
|
|
or
|
|
.I <signal.h>
|
|
or
|
|
.I <stropts.h>
|
|
or
|
|
.I <sys/ipc.h>
|
|
or
|
|
.I <sys/stat.h>
|
|
or
|
|
.IR <unistd.h> .
|
|
.IP
|
|
A type used to hold user IDs.
|
|
According to POSIX,
|
|
this shall be an integer type.
|
|
.IP
|
|
Conforming to: POSIX.1-2001 and later.
|
|
.IP
|
|
See also:
|
|
.BR chown (2),
|
|
.BR getuid (2),
|
|
.BR geteuid (2),
|
|
.BR getresuid (2),
|
|
.BR getpwnam (2),
|
|
.BR credentials (7)
|
|
.SH NOTES
|
|
The structures described in this manual page shall contain,
|
|
at least, the members shown in their definition, in no particular order.
|
|
.PP
|
|
Most of the integer types described in this page don't have
|
|
a corresponding length modifier for the
|
|
.BR printf (3)
|
|
and the
|
|
.BR scanf (3)
|
|
families of functions.
|
|
To print a value of an integer type that doesn't have a length modifier,
|
|
it should be converted to
|
|
.I intmax_t
|
|
or
|
|
.I uintmax_t
|
|
by an explicit cast.
|
|
To scan into a variable of an integer type
|
|
that doesn't have a length modifier,
|
|
an intermediate temporary variable of type
|
|
.I intmax_t
|
|
or
|
|
.I uintmax_t
|
|
should be used.
|
|
When copying from the temporary variable to the destination variable,
|
|
the value could overflow.
|
|
If the type has upper and lower limits,
|
|
the user should check that the value is within those limits,
|
|
before actually copying the value.
|
|
The example below shows how these conversions should be done.
|
|
.SH EXAMPLES
|
|
The program shown below scans from a string and prints a value stored in
|
|
a variable of an integer type that doesn't have a length modifier.
|
|
The appropriate conversions from and to
|
|
.IR intmax_t ,
|
|
and the appropriate range checks,
|
|
are used as explained in the notes section above.
|
|
.PP
|
|
.EX
|
|
#include <stdint.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <sys/types.h>
|
|
|
|
int
|
|
main (void)
|
|
{
|
|
static const char *const str = "500000 us in half a second";
|
|
suseconds_t us;
|
|
intmax_t tmp;
|
|
|
|
/* Scan the number from the string into the temporary variable */
|
|
|
|
sscanf(str, "%jd", &tmp);
|
|
|
|
/* Check that the value is within the valid range of suseconds_t */
|
|
|
|
if (tmp < \-1 || tmp > 1000000) {
|
|
fprintf(stderr, "Scanned value outside valid range!\en");
|
|
exit(EXIT_FAILURE);
|
|
}
|
|
|
|
/* Copy the value to the suseconds_t variable \(aqus\(aq */
|
|
|
|
us = tmp;
|
|
|
|
/* Even though suseconds_t can hold the value \-1, this isn\(aqt
|
|
a sensible number of microseconds */
|
|
|
|
if (us < 0) {
|
|
fprintf(stderr, "Scanned value shouldn\(aqt be negative!\en");
|
|
exit(EXIT_FAILURE);
|
|
}
|
|
|
|
/* Print the value */
|
|
|
|
printf("There are %jd microseconds in half a second.\en",
|
|
(intmax_t) us);
|
|
|
|
exit(EXIT_SUCCESS);
|
|
}
|
|
.EE
|
|
.SH SEE ALSO
|
|
.BR feature_test_macros (7),
|
|
.BR standards (7)
|