man-pages/man2/syscalls.2

.\" Copyright (C) 2007 Michael Kerrisk <mtk-manpages@gmx.net>
.\" with some input from Stepan Kasal <kasal@ucw.cz>
.\"
.\" Some content retained from an earlier version of this page:
.\" Copyright (C) 1998 Andries Brouwer (aeb@cwi.nl)
.\" Modifications for 2.2 and 2.4 Copyright (C) 2002 Ian Redfern
.\" <redferni@logica.com>
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.TH SYSCALLS 2 2007-07-07 "Linux" "Linux Programmer's Manual"
.SH NAME
syscalls \- Linux system calls
.SH SYNOPSIS
Linux system calls.
.SH DESCRIPTION
The system call is the fundamental interface between an application
and the Linux kernel.

This man page lists those system calls that are common to most platforms.
In the list, the
.I Kernel
column indicates the kernel version
for those system calls that were new in Linux 2.2,
or have appeared since that kernel version.
Note the following points:
.IP * 3
Where no kernel version is indicated,
the system call appeared in kernel 2.0 or earlier.
.IP *
Where a system call is marked "2.2"
this means the system call probably appeared in a 2.1.x kernel version,
and first appeared in a stable kernel with 2.2.0.
(No new system calls were added in the stable
kernel 2.0.x series.
The 2.2 kernel was created as a branch of kernel 2.0.21 via the 2.1.x
unstable kernel series)
.IP *
Where a system call is marked "2.4"
this means the system call probably appeared in a 2.3.x kernel version,
and first appeared in a stable kernel with 2.4.0.
(No new system calls were added in the stable
kernel 2.2.x series.
The 2.4 kernel was created as a branch of kernel 2.2.8 via the 2.3.x
unstable kernel series.)
.IP *
Where a system call is marked "2.6"
this means the system call probably appeared in a 2.5.x kernel version,
and first appeared in a stable kernel with 2.6.0.
.IP *
Starting with kernel 2.6.0, the development model changed,
and new system calls may appear in each 2.6.x release.
Kernel 2.6.0 was formed from a branch of kernel 2.4.15 via the 2.5.x
unstable kernel series.
In some cases, a system call appeared in 2.6.x and was also backported
into a 2.4.x release after 2.4.15;
where this is so, the version where the system call appeared
in both of the major kernel series is listed.
(Where a system call is listed as appearing in kernel 2.4.x, x <= 15,
then implicitly it also appeared in the later kernel 2.6.0.)
.PP
The list of system calls that are available as at kernel 2.6.22
(or in a few cases only on older kernels) is as follows:
.\"
.\" Looking at scripts/checksyscalls.sh in the kernel source is
.\" instructive about i386 specifics.
.\"
.TS
l l l
---
l l l.
System call	Kernel	Notes
\fB_llseek\fP(2)
\fB_newselect\fP(2)
\fB_sysctl\fP(2)
\fBaccept\fP(2)
\fBaccess\fP(2)
\fBacct\fP(2)
\fBadd_key\fP(2)	2.6.11
\fBadjtimex\fP(2)
\fBafs_syscall\fP(2)
\fBalarm\fP(2)
.\" alloc_hugepages (2) appeared in 2.5.36 and went away in 2.5.44
.\" in 2.4.x, the syscall number exists but give ENOSYS
\fBbdflush\fP(2)
\fBbind\fP(2)
\fBbreak\fP(2)
\fBbrk\fP(2)
\fBcacheflush\fP(2)		Various architectures;
		but not on i386
\fBcapget\fP(2)	2.2
\fBcapset\fP(2)	2.2
\fBchdir\fP(2)
\fBchmod\fP(2)
\fBchown\fP(2)
\fBchown32\fP(2)	2.4
\fBchroot\fP(2)
\fBclock_getres\fP(2)	2.6
\fBclock_gettime\fP(2)	2.6
\fBclock_nanosleep\fP(2)	2.6
\fBclock_settime\fP(2)	2.6
\fBclone\fP(2)
\fBclose\fP(2)
\fBconnect\fP(2)
\fBcreat\fP(2)
\fBcreate_module\fP(2)
\fBdelete_module\fP(2)
\fBdup\fP(2)
\fBdup2\fP(2)
\fBepoll_create\fP(2)	2.6
\fBepoll_ctl\fP(2)	2.6
\fBepoll_pwait\fP(2)	2.6.19
\fBepoll_wait\fP(2)	2.6
\fBeventfd\fP(2)	2.6.22
\fBexecve\fP(2)
\fBexit\fP(2)
\fBexit_group\fP(2)	2.6; 2.4.20
\fBfaccessat\fP(2)	2.6.16
\fBfadvise64\fP(2)	2.6	Implements \fBposix_fadvise\fP(2)
\fBfadvise64_64\fP(2)	2.6	Implements \fBposix_fadvise\fP(2)
\fBfchdir\fP(2)
\fBfchmod\fP(2)
\fBfchmodat\fP(2)	2.6.16
\fBfchown\fP(2)
\fBfchown32\fP(2)	2.4
\fBfchownat\fP(2)	2.6.16
\fBfcntl\fP(2)
\fBfcntl64\fP(2)	2.4
\fBfdatasync\fP(2)
\fBfgetxattr\fP(2)	2.6; 2.4.18
\fBflistxattr\fP(2)	2.6; 2.4.18
\fBflock\fP(2)
\fBfork\fP(2)
.\" free_hugepages (2) appeared in 2.5.36 and went away in 2.5.44
.\" in 2.4.x, the syscall number exists but give ENOSYS
\fBfremovexattr\fP(2)	2.6; 2.4.18
\fBfsetxattr\fP(2)	2.6; 2.4.18
\fBfstat\fP(2)
\fBfstat64\fP(2)	2.4
\fBfstatat64\fP(2)	2.6.16?
\fBfstatfs\fP(2)
\fBfstatfs64\fP(2)	2.6
\fBfsync\fP(2)
\fBftime\fP(2)		Implemented in glibc;
		see \fBftime\fP(3)
\fBftruncate\fP(2)
\fBftruncate64\fP(2)	2.4
\fBfutex\fP(2)	2.6; 2.4.19
\fBfutimesat\fP(2)	2.6.16
\fBget_kernel_syms\fP(2)
\fBget_mempolicy\fP(2)	2.6.6
\fBget_robust_list\fP(2)	2.6.17
\fBget_thread_area\fP(2)	2.6; 2.4.20
\fBgetcpu\fP(2)	2.6.19
\fBgetcwd\fP(2)	2.2
\fBgetdents\fP(2)
\fBgetdents64\fP(2)	2.4
\fBgetegid\fP(2)
\fBgetegid32\fP(2)	2.4
\fBgeteuid\fP(2)
\fBgeteuid32\fP(2)	2.4
\fBgetgid\fP(2)
\fBgetgid32\fP(2)	2.4
\fBgetgroups\fP(2)
\fBgetgroups32\fP(2)	2.4
\fBgetitimer\fP(2)
\fBgetpeername\fP(2)
\fBgetpagesize\fP(2)		Various architectures;
		but not on i386
\fBgetpgid\fP(2)
\fBgetpgrp\fP(2)
\fBgetpid\fP(2)
\fBgetpmsg\fP(2)	2.2	Reserved for STREAMS support
\fBgetppid\fP(2)
\fBgetpriority\fP(2)
\fBgetresgid\fP(2)	2.2
\fBgetresgid32\fP(2)	2.4
\fBgetresuid\fP(2)	2.2
\fBgetresuid32\fP(2)	2.4
\fBgetrlimit\fP(2)
\fBgetrusage\fP(2)
\fBgetsid\fP(2)
\fBgetsockname\fP(2)
\fBgetsockopt\fP(2)
\fBgettid\fP(2)	2.4.11
\fBgettimeofday\fP(2)
\fBgetuid\fP(2)
\fBgetuid32\fP(2)	2.4
\fBgetxattr\fP(2)	2.6; 2.4.18
\fBgtty\fP(2)
\fBidle\fP(2)
\fBinit_module\fP(2)
\fBinotify_add_watch\fP(2)	2.6.13
\fBinotify_init\fP(2)	2.6.13
\fBinotify_rm_watch\fP(2)	2.6.13
\fBio_cancel\fP(2)	2.6; 2.4.20
\fBio_destroy\fP(2)	2.6; 2.4.20
\fBio_getevents\fP(2)	2.6; 2.4.20
\fBio_setup\fP(2)	2.6; 2.4.20
\fBio_submit\fP(2)	2.6; 2.4.20
\fBioctl\fP(2)
\fBioperm\fP(2)
\fBiopl\fP(2)
\fBioprio_get\fP(2)	2.6.13
\fBioprio_set\fP(2)	2.6.13
\fBipc\fP(2)		Implements System V IPC calls
\fBkexec_load\fP(2)	2.6.7	Was named sys_kexec_load()
		from 2.6.7 to 2.6.16
\fBkeyctl\fP(2)	2.6.11
\fBkill\fP(2)
\fBlchown\fP(2)	2.2
\fBlchown32\fP(2)	2.4
\fBlgetxattr\fP(2)	2.6; 2.4.18
\fBlink\fP(2)
\fBlinkat\fP(2)	2.6.16
\fBlisten\fP(2)
\fBlistxattr\fP(2)	2.6; 2.4.18
\fBllistxattr\fP(2)	2.6; 2.4.18
\fBlock\fP(2)
\fBlookup_dcookie\fP(2)	2.6
\fBlremovexattr\fP(2)	2.6; 2.4.18
\fBlseek\fP(2)
\fBlsetxattr\fP(2)	2.6; 2.4.18
\fBlstat\fP(2)
\fBlstat64\fP(2)	2.4
\fBmadvise\fP(2)	2.4
\fBmadvise1\fP(2)	2.4
\fBmbind\fP(2)	2.6.6
.\" \fBmemory_ordering\fP(2)	???	Sparc64
\fBmigrate_pages\fP(2)	2.6.16
\fBmincore\fP(2)	2.4
\fBmkdir\fP(2)
\fBmkdirat\fP(2)	2.6.16
\fBmknod\fP(2)
\fBmknodat\fP(2)	2.6.16
\fBmlock\fP(2)
\fBmlockall\fP(2)
\fBmmap\fP(2)
\fBmmap2\fP(2)	2.4
\fBmodify_ldt\fP(2)
\fBmount\fP(2)
\fBmove_pages\fP(2)	2.6.18
\fBmprotect\fP(2)
\fBmpx\fP(2)
\fBmq_getsetattr\fP(2)	2.6.6	Implements \fBmq_getattr\fP(3)
		and \fBmq_setattr\fP(3)
\fBmq_notify\fP(2)	2.6.6
\fBmq_open\fP(2)	2.6.6
\fBmq_timedreceive\fP(2)	2.6.6
\fBmq_timedsend\fP(2)	2.6.6
\fBmq_unlink\fP(2)
\fBmremap\fP(2)
\fBmsgctl\fP(2)
\fBmsgget\fP(2)
\fBmsgrcv\fP(2)
\fBmsgsnd\fP(2)
\fBmsync\fP(2)
\fBmunlock\fP(2)
\fBmunlockall\fP(2)
\fBmunmap\fP(2)
\fBnanosleep\fP(2)
\fBnfsservctl\fP(2)	2.2
\fBnice\fP(2)
\fBoldfstat\fP(2)
\fBoldlstat\fP(2)
\fBoldolduname\fP(2)
\fBoldstat\fP(2)
\fBolduname\fP(2)
\fBopen\fP(2)
\fBopenat\fP(2)	2.6.16
\fBpause\fP(2)
.\" \fBpciconfig_iobase\fP(2)	???	Alpha, PowerPC, ARM
.\" \fBpciconfig_read\fP(2)	???	Alpha, PowerPC, ARM
.\" \fBpciconfig_write\fP(2)	???	Alpha, PowerPC, ARM
\fBpersonality\fP(2)
.\" \fBperfctr\fP(2)	???	Sparc32, Sparc64
.\" \fBperfmonctl\fP(2)	???	IA-64
\fBphys\fP(2)		Unimplemented (no slot
		since 2.1.116)
\fBpipe\fP(2)
\fBpivot_root\fP(2)	2.5
\fBpoll\fP(2)	2.2
\fBppoll\fP(2)	2.6.16
\fBprctl\fP(2)	2.2
\fBpread64\fP(2)		Added as "pread" in 2.2;
		renamed "pread64" in 2.6
\fBprof\fP(2)
\fBprofil\fP(2)		Implemented in glibc;
		see \fBprofil\fP(3)
\fBpselect6\fP(2)	2.6.16	Implements \fBpselect\fP(2)
\fBptrace\fP(2)
\fBputpmsg\fP(2)	2.2	Reserved for STREAMS support
\fBpwrite64\fP(2)		Added as "pwrite" in 2.2;
		renamed "pwrite64" in 2.6
\fBquery_module\fP(2)	2.2
\fBquotactl\fP(2)
\fBread\fP(2)
\fBreadahead\fP(2)	2.4.13
\fBreaddir\fP(2)		Superseded by \fBgetdents\fP(2)
\fBreadlink\fP(2)
\fBreadlinkat\fP(2)	2.6.16
\fBreadv\fP(2)
\fBreboot\fP(2)
\fBrecv\fP(2)
\fBrecvfrom\fP(2)
\fBrecvmsg\fP(2)
\fBremap_file_pages\fP(2)	2.6
\fBremovexattr\fP(2)	2.6; 2.4.18
\fBrename\fP(2)
\fBrenameat\fP(2)	2.6.16
\fBrequest_key\fP(2)	2.6.11
\fBrestart_syscall\fP(2)	2.6
\fBrmdir\fP(2)
\fBrt_sigaction\fP(2)	2.2
\fBrt_sigpending\fP(2)	2.2
\fBrt_sigprocmask\fP(2)	2.2
\fBrt_sigqueueinfo\fP(2)	2.2	Implements \fBsigqueue\fP(2)
\fBrt_sigreturn\fP(2)	2.2
\fBrt_sigsuspend\fP(2)	2.2
\fBrt_sigtimedwait\fP(2)	2.2
\fBsched_get_priority_max\fP(2)
\fBsched_get_priority_min\fP(2)
\fBsched_getaffinity\fP(2)	2.6; 2.4.19
\fBsched_getparam\fP(2)
\fBsched_getscheduler\fP(2)
\fBsched_rr_get_interval\fP(2)
\fBsched_setaffinity\fP(2)	2.6; 2.4.19
\fBsched_setparam\fP(2)
\fBsched_setscheduler\fP(2)
\fBsched_yield\fP(2)
.\" 2.4.11 added security(2), but this was dropped in 2.5.x
.\" \fBsecurity\fP(2)
.\" (2.4.11; not in 2.6)
\fBselect\fP(2)
\fBsemctl\fP(2)
\fBsemget\fP(2)
\fBsemop\fP(2)
\fBsemtimedop\fP(2)	2.6; 2.4.22
\fBsend\fP(2)
\fBsendfile\fP(2)	2.2
\fBsendfile64\fP(2)	2.6; 2.4.19
\fBsendmsg\fP(2)
\fBsendto\fP(2)
\fBset_mempolicy\fP(2)	2.6.6
\fBset_robust_list\fP(2)	2.6.17
\fBset_thread_area\fP(2)	2.6; 2.4.20
\fBset_tid_address\fP(2)	2.6
\fBset_zone_reclaim\fP(2)	2.6.13	Removed in 2.6.16
\fBsetdomainname\fP(2)
\fBsetfsgid\fP(2)
\fBsetfsgid32\fP(2)	2.4
\fBsetfsuid\fP(2)
\fBsetfsuid32\fP(2)	2.4
\fBsetgid\fP(2)
\fBsetgid32\fP(2)	2.4
\fBsetgroups\fP(2)
\fBsetgroups32\fP(2)	2.4
\fBsethostname\fP(2)
\fBsetitimer\fP(2)
\fBsetpgid\fP(2)
\fBsetpriority\fP(2)
\fBsetregid\fP(2)
\fBsetregid32\fP(2)	2.4
\fBsetresgid\fP(2)	2.2
\fBsetresgid32\fP(2)	2.4
\fBsetresuid\fP(2)	2.2
\fBsetresuid32\fP(2)	2.4
\fBsetreuid\fP(2)
\fBsetreuid32\fP(2)	2.4
\fBsetrlimit\fP(2)
\fBsetsid\fP(2)
\fBsetsockopt\fP(2)
\fBsettimeofday\fP(2)
\fBsetuid\fP(2)
\fBsetuid32\fP(2)	2.4
\fBsetup\fP(2)		Removed in 2.2
\fBsetxattr\fP(2)	2.6; 2.4.18
\fBsgetmask\fP(2)
\fBshmat\fP(2)
\fBshmctl\fP(2)
\fBshmdt\fP(2)
\fBshmget\fP(2)
\fBshutdown\fP(2)
\fBsigaction\fP(2)
\fBsigaltstack\fP(2)	2.2
\fBsignal\fP(2)
\fBsignalfd\fP(2)	2.6.22
\fBsigpending\fP(2)
\fBsigprocmask\fP(2)
\fBsigreturn\fP(2)
\fBsigsuspend\fP(2)
\fBsocket\fP(2)
\fBsocketcall\fP(2)		Implements BSD socket calls
\fBsocketpair\fP(2)
\fBsplice\fP(2)	2.6.17
.\"  \fBspu_create\fP(2)	2.6.16	PowerPC only
.\"  \fBspu_run\fP(2)	2.6.16	PowerPC only
\fBssetmask\fP(2)
\fBstat\fP(2)
\fBstat64\fP(2)	2.4
\fBstatfs\fP(2)
\fBstatfs64\fP(2)	2.6
\fBstime\fP(2)
\fBstty\fP(2)
\fBswapoff\fP(2)
\fBswapon\fP(2)
\fBsymlink\fP(2)
\fBsymlinkat\fP(2)	2.6.16
\fBsync\fP(2)
\fBsync_file_range\fP(2)	2.6.17
\fBsysfs\fP(2)
\fBsysinfo\fP(2)
\fBsyslog\fP(2)		glibc interface is \fBklogctl\fP(3)
\fBtee\fP(2)	2.6.17
\fBtgkill\fP(2)	2.6
\fBtime\fP(2)
\fBtimer_create\fP(2)	2.6
\fBtimer_delete\fP(2)	2.6
\fBtimer_getoverrun\fP(2)	2.6
\fBtimer_gettime\fP(2)	2.6
\fBtimer_settime\fP(2)	2.6
\fBtimerfd\fP(2)	2.6.22
\fBtimes\fP(2)
\fBtkill\fP(2)	2.6; 2.4.22
\fBtruncate\fP(2)
\fBtruncate64\fP(2)	2.4
\fBugetrlimit\fP(2)	2.4
\fBulimit\fP(2)		Implemented in glibc;
		see \fBulimit\fP(3)
\fBumask\fP(2)
\fBumount\fP(2)
.\" sys_oldumount() -- __NR_umount
\fBumount2\fP(2)	2.2
.\" sys_umount() -- __NR_umount2
\fBuname\fP(2)
\fBunlink\fP(2)
\fBunlinkat\fP(2)	2.6.16
\fBunshare\fP(2)	2.6.16
\fBuselib\fP(2)
\fBustat\fP(2)
\fButime\fP(2)
\fButimensat\fP(2)	2.6.22
\fButimes\fP(2)	2.6
\fBvfork\fP(2)
\fBvhangup\fP(2)
\fBvm86old\fP(2)		Superseded by \fBvm86\fP(2)
\fBvmsplice\fP(2)	2.6.17
\fBvserver\fP(2)	2.6
\fBwait4\fP(2)
\fBwaitid\fP(2)	2.6.10
\fBwaitpid\fP(2)
\fBwrite\fP(2)
\fBwritev\fP(2)
.TE
.PP
Note the following points:
.\" .IP * 3
.\" These system calls are obsolete:
.\" getrlimit,
.\" .\" .\" oldfstat,
.\" .\" .\" oldlstat,
.\" .\" .\" oldolduname,
.\" .\" .\" oldstat,
.\" .\" .\" olduname,
.\" .\" .\" readdir,
.\" .\" .\" select,
.\" .\" .\" and
.\" .\" .\" vm86old
.IP * 3
Although slots are reserved for them in the system call table,
the following system calls are not implemented in the standard kernel: 
.BR afs_syscall (2), \" __NR_afs_syscall is 53 on Linux 2.6.22/i386
.BR break (2),       \" __NR_break is 17 on Linux 2.6.22/i386
.BR ftime (2),       \" __NR_ftime is 35 on Linux 2.6.22/i386
.BR getpmsg (2),     \" __NR_getpmsg is 188 on Linux 2.6.22/i386
.BR gtty (2),        \" __NR_gtty is 32 on Linux 2.6.22/i386
.BR idle (2),        \" __NR_idle is 112 on Linux 2.6.22/i386
.BR lock (2),        \" __NR_lock is 53 on Linux 2.6.22/i386
.BR madvise1 (2),    \" __NR_madvise1 is 219 on Linux 2.6.22/i386
.BR mpx (2),         \" __NR_mpx is 66 on Linux 2.6.22/i386
.BR phys (2),        \" Slot has been re-used
.BR prof (2),        \" __NR_prof is 44 on Linux 2.6.22/i386
.BR profil (2),      \" __NR_profil is 98 on Linux 2.6.22/i386
.BR putpmsg (2),     \" __NR_putpmsg is 189 on Linux 2.6.22/i386
.BR security (2),
.\" __NR_putpmsg is 223 on Linux 2.4/i386; absent on 2.6/i386, present
.\" on a a couple og 2.6 architectures
.BR stty (2),        \" __NR_stty is 31 on Linux 2.6.22/i386
.BR ulimit (2),      \" __NR_ulimit is 58 on Linux 2.6.22/i386
and
.BR vserver (2)      \" __NR_vserver is 273 on Linux 2.6.22/i386
(see also
.BR unimplemented (2)).
However,
.BR ftime (3),
.BR profil (3)
and
.BR ulimit (3)
exist as library routines.
The slot for
.BR phys (2)
is in use since kernel 2.1.116 for
.BR umount (2);
.BR phys (2) 
will never be implemented.
.IP *
The
.BR getpmsg (2)
and
.BR putpmsg (2)
calls are for kernels patched to support STREAMS,
and may never be in the standard kernel.
.\" The security call is for future use.
.PP
Roughly speaking, the code belonging to the system call
with number __NR_xxx defined in
.I /usr/include/asm/unistd.h
can be found in the kernel source in the routine
.IR sys_xxx ().
(The dispatch table for i386 can be found in
.IR /usr/src/linux/arch/i386/kernel/entry.S .)
There are many exceptions, however, mostly because
older system calls were superseded by newer ones,
and this has been treated somewhat unsystematically.
On platforms with
proprietary OS emulation, such as parisc, sparc, sparc64 and alpha,
there are many additional system calls; mips64 also contains a full
set of 32-bit system calls.

Over time, changes to the interfaces of some system calls have been
necessary.
One reason for such changes was the need to increase the size of
structures or scalar values passed to the system call.
Because of these changes, there are now multiple implementations
of certain system calls.
These different versions are incompatible at the binary level,
but applications are generally unaware of this: glibc does some magic
to ensure that existing binaries use the version of the system
call that was current when the binary was created,
so that ABI compatibility is preserved.
Examples of systems calls that exist in multiple versions are
the following:
.IP * 3
By now there are three different implementations of
.BR stat (2):
.IR sys_stat ()
(slot
.IR __NR_oldstat ),
.IR sys_newstat ()
(slot
.IR __NR_stat ),
and
.IR sys_stat64()
(slot
.IR __NR_stat64 ),
with the last being the most current.
.\" e.g., on 2.6.22/x86: __NR_oldstat 18, __NR_stat 106, __NR_stat64 195
.\" The stat system calls deal with three different data structures,
.\" defined in include/asm-i386/stat.h: __old_kernel_stat, stat, stat64
A similar story applies for
.BR lstat (2)
and
.BR fstat (2).
.IP *
Similarly, the defines
.IR __NR_oldolduname ,
.IR __NR_olduname ,
and
.IR __NR_uname
refer to the routines
.IR sys_olduname (),
.IR sys_uname ()
and
.IR sys_newuname ().
.IP *
In Linux 2.0,
a new version of
.BR vm86 (2)
appeared, with the old and the new kernel routines being named
.IR sys_vm86old ()
and
.IR sys_vm86 ().
.IP *
In Linux 2.4,
a new version of
.BR getrlimit (2)
appeared, with the old and the new kernel routines being named
.IR sys_old_getrlimit ()
(slot
.IR __NR_getrlimit )
and
.IR sys_getrlimit ()
(slot
.IR __NR_ugetrlimit ).
.IP *
Linux 2.4 increased the size of user and group IDs from 16 to 32 bits.
.\" 64 bit off_t changes: ftruncate64, *stat64,
.\" fcntl64 (because of the flock structure), getdents64, *statfs64
To support this change, a range of system calls were added
(e.g.,
.BR chown32 (2),
.BR getuid32 (2),
.BR getgroups32 (2),
.BR setresuid32 (2)),
superseding earlier calls of the same name without the
"32" suffix.
.IP *
Linux 2.4 added support for applications on 32-bit architectures
to access large files (i.e., files for which the sizes and
file offsets can't be represented in 32 bits.)
To support this change, replacements were required for system calls
that deal with file offsets and sizes.
Thus the following system calls were added:
.BR fcntl64 (2),
.BR ftruncate64 (2),
.BR getdents64 (2),
.BR stat64 (2),
.BR statfs64 (2),
and their analogs that work with file descriptors or
symbolic links.
These system calls supersede the older system calls
which, except in the case of the "stat" calls,
have the same name without the "64" suffix.
.sp
On newer platforms that only have 64-bit file access and 32-bit uids
(e.g., alpha, ia64, s390x) there are no *64 or *32 calls.
Where the *64 and *32 calls exist, the other versions are obsolete.
.IP *
The
.I rt_sig*
calls were added in kernel 2.2 to support the addition
of real-time signals (see
.BR signal (7)).
These system calls supersede the older system calls of the same
name without the "rt_" prefix.
.IP *
It is different with
.B select (2)
and
.BR mmap (2).
These use five or more parameters, and caused problems the way
parameter passing on the i386 used to be set up.
Thus, while
other architectures have
.IR sys_select ()
and
.IR sys_mmap ()
corresponding to
.IR __NR_select
and
.IR __NR_mmap ,
on i386 one finds
.IR old_select ()
and
.IR old_mmap ()
(routines that use a pointer to a
parameter block) instead.
These days passing five parameters
is not a problem any more, and there is a
.IR __NR__newselect
(used by
libc 6) that corresponds directly to
.IR sys_select ()
and similarly
.IR __NR_mmap2.
.PP
Two system call numbers,
.IR __NR__llseek
and
.IR __NR__sysctl
have an additional underscore absent in
.IR sys_llseek ()
and
.IR sys_sysctl ().

On many platforms, including i386, socket calls are all multiplexed
through
.BR socketcall (2)
and System V IPC calls are multiplexed through
.BR ipc (2).

In kernel 2.1.81,
.BR lchown (2)
and 
.BR chown (2)
were swapped; that is,
.BR lchown (2)
was added with the semantics that were then current for
.BR chown (2),
and the semantics of the latter call were changed to what
they are today.
.SH SEE ALSO
.BR syscall (2),
.BR unimplemented (2)