man2/syscalls.2

   1 .\" Copyright (C) 2007 Michael Kerrisk <mtk.manpages@gmail.com>
   2 .\" with some input from Stepan Kasal <kasal@ucw.cz>
   3 .\"
   4 .\" Some content retained from an earlier version of this page:
   5 .\" Copyright (C) 1998 Andries Brouwer (aeb@cwi.nl)
   6 .\" Modifications for 2.2 and 2.4 Copyright (C) 2002 Ian Redfern
   7 .\" <redferni@logica.com>
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  28 .\"
  29 .TH SYSCALLS 2 2013-02-10 "Linux" "Linux Programmer's Manual"
  30 .SH NAME
  31 syscalls \- Linux system calls
  32 .SH SYNOPSIS
  33 Linux system calls.
  34 .SH DESCRIPTION
  35 The system call is the fundamental interface between an application
  36 and the Linux kernel.
  37 .SS System calls and library wrapper functions
  38 System calls are generally not invoked directly,
  39 but rather via wrapper functions in glibc (or perhaps some other library).
  40 For details of direct invocation of a system call, see
  41 .BR intro (2).
  42 Often, but not always, the name of the wrapper function is the same
  43 as the name of the system call that it invokes.
  44 For example, glibc contains a function
  45 .BR truncate ()
  46 which invokes the underlying "truncate" system call.
  47
  48 Often the glibc wrapper function is quite thin, doing little work
  49 other than copying arguments to the right registers
  50 before invoking the system call,
  51 and then setting
  52 .I errno
  53 appropriately after the system call has returned.
  54 (These are the same steps that are performed by
  55 .BR syscall (2),
  56 which can be used to invoke system calls
  57 for which no wrapper function is provided.)
  58 Note: system calls indicate a failure by returning a negative error
  59 number to the caller;
  60 when this happens,
  61 the wrapper function negates the returned error number
  62 (to make it positive), copies it to
  63 .IR errno ,
  64 and returns \-1 to the caller of the wrapper.
  65
  66 Sometimes, however, the wrapper function does some extra work
  67 before invoking the system call.
  68 For example, nowadays there are (for reasons described below) two
  69 related system calls,
  70 .BR truncate (2)
  71 and
  72 .BR truncate64 (2),
  73 and the glibc
  74 .BR truncate ()
  75 wrapper function checks which of those system calls
  76 are provided by the kernel and determines which should be employed.
  77 .SS System call list
  78 Below is a list of those system calls that are common to most platforms.
  79 In the list, the
  80 .I Kernel
  81 column indicates the kernel version
  82 for those system calls that were new in Linux 2.2,
  83 or have appeared since that kernel version.
  84 Note the following points:
  85 .IP * 3
  86 Where no kernel version is indicated,
  87 the system call appeared in kernel 1.0 or earlier.
  88 .IP *
  89 Where a system call is marked "1.2"
  90 this means the system call probably appeared in a 1.1.x kernel version,
  91 and first appeared in a stable kernel with 1.2.
  92 (Development of the 1.2 kernel was initiated from a branch of kernel
  93 1.0.6 via the 1.1.x unstable kernel series.)
  94 .IP *
  95 Where a system call is marked "2.0"
  96 this means the system call probably appeared in a 1.3.x kernel version,
  97 and first appeared in a stable kernel with 2.0.
  98 (Development of the 2.0 kernel was initiated from a branch of kernel
  99 1.2.x, somewhere around 1.2.10,
 100 via the 1.3.x unstable kernel series.)
 101 .\" Was kernel 2.0 started from a branch of 1.2.10?
 102 .\" At least from the timestamps of the tarballs of
 103 .\" of 1.2.10 and 1.3.0, that's how it looks, but in
 104 .\" fact the diff doesn't seem very clear, the
 105 .\" 1.3.0 .tar.bz is much bigger (2.0 MB) than the
 106 .\" 1.2.10 .tar.bz2 (1.8 MB), and AEB points out the
 107 .\" timestamps of some files in 1.3.0 seem to be older
 108 .\" than those in 1.2.10.  All of this suggests
 109 .\" that there might not have been a clean branch point.
 110 .IP *
 111 Where a system call is marked "2.2"
 112 this means the system call probably appeared in a 2.1.x kernel version,
 113 and first appeared in a stable kernel with 2.2.0.
 114 (Development of the 2.2 kernel was initiated from a branch of kernel
 115 2.0.21 via the 2.1.x unstable kernel series.)
 116 .IP *
 117 Where a system call is marked "2.4"
 118 this means the system call probably appeared in a 2.3.x kernel version,
 119 and first appeared in a stable kernel with 2.4.0.
 120 (Development of the 2.4 kernel was initiated from a branch of
 121 kernel 2.2.8 via the 2.3.x unstable kernel series.)
 122 .IP *
 123 Where a system call is marked "2.6"
 124 this means the system call probably appeared in a 2.5.x kernel version,
 125 and first appeared in a stable kernel with 2.6.0.
 126 (Development of kernel 2.6 was initiated from a branch
 127 of kernel 2.4.15 via the 2.5.x unstable kernel series.)
 128 .IP *
 129 Starting with kernel 2.6.0, the development model changed,
 130 and new system calls may appear in each 2.6.x release.
 131 In this case, the exact version number where the system call appeared
 132 is shown.
 133 This convention continues with the 3.x kernel series,
 134 which followed on from kernel 2.6.39.
 135 .IP *
 136 In some cases, a system call was added to a stable kernel
 137 series after it branched from the previous stable kernel
 138 series, and then backported into the earlier stable kernel series.
 139 For example some system calls that appeared in 2.6.x were also backported
 140 into a 2.4.x release after 2.4.15.
 141 When this is so, the version where the system call appeared
 142 in both of the major kernel series is listed.
 143 .PP
 144 The list of system calls that are available as at kernel 3.5
 145 (or in a few cases only on older kernels) is as follows:
 146 .\"
 147 .\" Looking at scripts/checksyscalls.sh in the kernel source is
 148 .\" instructive about x86 specifics.
 149 .\"
 150 .ad l
 151 .TS
 152 l l l
 153 ---
 154 l l l.
 155 \fBSystem call\fP       \fBKernel\fP    \fBNotes\fP
 156
 157 \fB_llseek\fP(2)        1.2
 158 \fB_newselect\fP(2)
 159 \fB_sysctl\fP(2)
 160 \fBaccept\fP(2)
 161 \fBaccept4\fP(2)        2.6.28
 162 \fBaccess\fP(2)
 163 \fBacct\fP(2)
 164 \fBadd_key\fP(2)        2.6.11
 165 \fBadjtimex\fP(2)
 166 \fBalarm\fP(2)
 167 \fBalloc_hugepages\fP(2)        2.5.36  Removed in 2.5.44
 168 \fBbdflush\fP(2)                T{
 169 Deprecated (does nothing) since 2.6
 170 T}
 171 \fBbind\fP(2)
 172 \fBbrk\fP(2)
 173 \fBcacheflush\fP(2)     1.2     Not on x86
 174 \fBcapget\fP(2) 2.2
 175 \fBcapset\fP(2) 2.2
 176 \fBchdir\fP(2)
 177 \fBchmod\fP(2)
 178 \fBchown\fP(2)
 179 \fBchown32\fP(2)        2.4
 180 \fBchroot\fP(2)
 181 \fBclock_adjtime\fP(2)  2.6.39
 182 \fBclock_getres\fP(2)   2.6
 183 \fBclock_gettime\fP(2)  2.6
 184 \fBclock_nanosleep\fP(2)        2.6
 185 \fBclock_settime\fP(2)  2.6
 186 \fBclone\fP(2)
 187 \fBclose\fP(2)
 188 \fBconnect\fP(2)
 189 \fBcreat\fP(2)
 190 \fBcreate_module\fP(2)          Removed in 2.6
 191 \fBdelete_module\fP(2)
 192 \fBdup\fP(2)
 193 \fBdup2\fP(2)
 194 \fBdup3\fP(2)   2.6.27
 195 \fBepoll_create\fP(2)   2.6
 196 \fBepoll_create1\fP(2)  2.6.27
 197 \fBepoll_ctl\fP(2)      2.6
 198 \fBepoll_pwait\fP(2)    2.6.19
 199 \fBepoll_wait\fP(2)     2.6
 200 \fBeventfd\fP(2)        2.6.22
 201 \fBeventfd2\fP(2)       2.6.27
 202 \fBexecve\fP(2)
 203 \fBexit\fP(2)
 204 \fBexit_group\fP(2)     2.6
 205 \fBfaccessat\fP(2)      2.6.16
 206 \fBfadvise64\fP(2)      2.6
 207 .\" Implements \fBposix_fadvise\fP(2)
 208 \fBfadvise64_64\fP(2)   2.6
 209 \fBfallocate\fP(2)      2.6.23
 210 \fBfanotify_init\fP(2)  2.6.37
 211 \fBfanotify_mark\fP(2)  2.6.37
 212 .\" The fanotify calls were added in Linux 2.6.36,
 213 .\" but disabled while the API was finalized.
 214 \fBfchdir\fP(2)
 215 \fBfchmod\fP(2)
 216 \fBfchmodat\fP(2)       2.6.16
 217 \fBfchown\fP(2)
 218 \fBfchown32\fP(2)       2.4
 219 \fBfchownat\fP(2)       2.6.16
 220 \fBfcntl\fP(2)
 221 \fBfcntl64\fP(2)        2.4
 222 \fBfdatasync\fP(2)
 223 \fBfgetxattr\fP(2)      2.6; 2.4.18
 224 \fBfinit_module\fP(2)   3.8
 225 \fBflistxattr\fP(2)     2.6; 2.4.18
 226 \fBflock\fP(2)  2.0
 227 \fBfork\fP(2)
 228 \fBfree_hugepages\fP(2) 2.5.36  Removed in 2.5.44
 229 \fBfremovexattr\fP(2)   2.6; 2.4.18
 230 \fBfsetxattr\fP(2)      2.6; 2.4.18
 231 \fBfstat\fP(2)
 232 \fBfstat64\fP(2)        2.4
 233 \fBfstatat64\fP(2)      2.6.16
 234 \fBfstatfs\fP(2)
 235 \fBfstatfs64\fP(2)      2.6
 236 \fBfsync\fP(2)
 237 \fBftruncate\fP(2)
 238 \fBftruncate64\fP(2)    2.4
 239 \fBfutex\fP(2)  2.6
 240 \fBfutimesat\fP(2)      2.6.16
 241 \fBget_kernel_syms\fP(2)                Removed in 2.6
 242 \fBget_mempolicy\fP(2)  2.6.6
 243 \fBget_robust_list\fP(2)        2.6.17
 244 \fBget_thread_area\fP(2)        2.6
 245 \fBgetcpu\fP(2) 2.6.19
 246 \fBgetcwd\fP(2) 2.2
 247 \fBgetdents\fP(2)       2.0
 248 \fBgetdents64\fP(2)     2.4
 249 \fBgetegid\fP(2)
 250 \fBgetegid32\fP(2)      2.4
 251 \fBgeteuid\fP(2)
 252 \fBgeteuid32\fP(2)      2.4
 253 \fBgetgid\fP(2)
 254 \fBgetgid32\fP(2)       2.4
 255 \fBgetgroups\fP(2)
 256 \fBgetgroups32\fP(2)    2.4
 257 \fBgetitimer\fP(2)
 258 \fBgetpeername\fP(2)
 259 \fBgetpagesize\fP(2)    2.0     Not on x86
 260 \fBgetpgid\fP(2)
 261 \fBgetpgrp\fP(2)
 262 \fBgetpid\fP(2)
 263 \fBgetppid\fP(2)
 264 \fBgetpriority\fP(2)
 265 \fBgetresgid\fP(2)      2.2
 266 \fBgetresgid32\fP(2)    2.4
 267 \fBgetresuid\fP(2)      2.2
 268 \fBgetresuid32\fP(2)    2.4
 269 \fBgetrlimit\fP(2)
 270 \fBgetrusage\fP(2)
 271 \fBgetsid\fP(2) 2.0
 272 \fBgetsockname\fP(2)
 273 \fBgetsockopt\fP(2)
 274 \fBgettid\fP(2) 2.4.11
 275 \fBgettimeofday\fP(2)
 276 \fBgetuid\fP(2)
 277 \fBgetuid32\fP(2)       2.4
 278 .\" \fBgetunwind\fP(2)  2.4.8   ia64; DEPRECATED
 279 \fBgetxattr\fP(2)       2.6; 2.4.18
 280 \fBinit_module\fP(2)
 281 \fBinotify_add_watch\fP(2)      2.6.13
 282 \fBinotify_init\fP(2)   2.6.13
 283 \fBinotify_init1\fP(2)  2.6.27
 284 \fBinotify_rm_watch\fP(2)       2.6.13
 285 \fBio_cancel\fP(2)      2.6
 286 \fBio_destroy\fP(2)     2.6
 287 \fBio_getevents\fP(2)   2.6
 288 \fBio_setup\fP(2)       2.6
 289 \fBio_submit\fP(2)      2.6
 290 \fBioctl\fP(2)
 291 \fBioperm\fP(2)
 292 \fBiopl\fP(2)
 293 \fBioprio_get\fP(2)     2.6.13
 294 \fBioprio_set\fP(2)     2.6.13
 295 \fBipc\fP(2)
 296 .\" Implements System V IPC calls
 297 \fBkcmp\fP(2)   3.5
 298 \fBkern_features\fP(2)  3.7     Sparc64
 299 \fBkexec_load\fP(2)     2.6.13
 300 .\" The entry in the syscall table was reserved starting in 2.6.7
 301 .\" Was named sys_kexec_load() from 2.6.7 to 2.6.16
 302 \fBkeyctl\fP(2) 2.6.11
 303 \fBkill\fP(2)
 304 \fBlchown\fP(2) 2.2
 305 \fBlchown32\fP(2)       2.4
 306 \fBlgetxattr\fP(2)      2.6; 2.4.18
 307 \fBlink\fP(2)
 308 \fBlinkat\fP(2) 2.6.16
 309 \fBlisten\fP(2)
 310 \fBlistxattr\fP(2)      2.6; 2.4.18
 311 \fBllistxattr\fP(2)     2.6; 2.4.18
 312 \fBlookup_dcookie\fP(2) 2.6
 313 \fBlremovexattr\fP(2)   2.6; 2.4.18
 314 \fBlseek\fP(2)
 315 \fBlsetxattr\fP(2)      2.6; 2.4.18
 316 \fBlstat\fP(2)
 317 \fBlstat64\fP(2)        2.4
 318 \fBmadvise\fP(2)        2.4
 319 \fBmadvise1\fP(2)       2.4
 320 \fBmbind\fP(2)  2.6.6
 321 .\" \fBmemory_ordering\fP(2)    ???     Sparc64
 322 \fBmigrate_pages\fP(2)  2.6.16
 323 \fBmincore\fP(2)        2.4
 324 \fBmkdir\fP(2)
 325 \fBmkdirat\fP(2)        2.6.16
 326 \fBmknod\fP(2)
 327 \fBmknodat\fP(2)        2.6.16
 328 \fBmlock\fP(2)
 329 \fBmlockall\fP(2)
 330 \fBmmap\fP(2)
 331 \fBmmap2\fP(2)  2.4
 332 \fBmodify_ldt\fP(2)
 333 \fBmount\fP(2)
 334 \fBmove_pages\fP(2)     2.6.18
 335 \fBmprotect\fP(2)
 336 \fBmq_getsetattr\fP(2)  2.6.6
 337 .\" Implements \fBmq_getattr\fP(3) and \fBmq_setattr\fP(3)
 338 \fBmq_notify\fP(2)      2.6.6
 339 \fBmq_open\fP(2)        2.6.6
 340 \fBmq_timedreceive\fP(2)        2.6.6
 341 \fBmq_timedsend\fP(2)   2.6.6
 342 \fBmq_unlink\fP(2)
 343 \fBmremap\fP(2) 2.0
 344 \fBmsgctl\fP(2)
 345 \fBmsgget\fP(2)
 346 \fBmsgrcv\fP(2)
 347 \fBmsgsnd\fP(2)
 348 \fBmsync\fP(2)  2.0
 349 .\" \fBmultiplexer\fP(2)        ??      __NR_multiplexer reserved on
 350 .\"             PowerPC, but unimplemented?
 351 \fBmunlock\fP(2)
 352 \fBmunlockall\fP(2)
 353 \fBmunmap\fP(2)
 354 \fBname_to_handle_at\fP(2)      2.6.39
 355 \fBnanosleep\fP(2)      2.0
 356 \fBnfsservctl\fP(2)     2.2     Removed in 3.1
 357 \fBnice\fP(2)
 358 \fBoldfstat\fP(2)
 359 \fBoldlstat\fP(2)
 360 \fBoldolduname\fP(2)
 361 \fBoldstat\fP(2)
 362 \fBolduname\fP(2)
 363 \fBopen\fP(2)
 364 \fBopen_by_handle_at\fP(2)      2.6.39
 365 \fBopenat\fP(2) 2.6.16
 366 \fBpause\fP(2)
 367 \fBpciconfig_iobase\fP(2)       2.2.15; 2.4     Not on x86
 368 .\" Alpha, PowerPC, ARM; not x86
 369 \fBpciconfig_read\fP(2) 2.0.26; 2.2     Not on x86
 370 .\" , PowerPC, ARM; not x86
 371 \fBpciconfig_write\fP(2)        2.0.26; 2.2     Not on x86
 372 .\" , PowerPC, ARM; not x86
 373 \fBperf_event_open\fP(2)        2.6.31  T{
 374 Was called perf_counter_open() in 2.6.31; renamed in 2.6.32
 375 T}
 376 \fBpersonality\fP(2)    1.2
 377 \fBperfctr\fP(2)        2.2     Sparc; removed in 2.6.34
 378 .\"     commit c7d5a0050773e98d1094eaa9f2a1a793fafac300 removed perfctr()
 379 .\" \fBperfmonctl\fP(2) ???     ia64
 380 \fBpipe\fP(2)
 381 \fBpipe2\fP(2)  2.6.27
 382 \fBpivot_root\fP(2)     2.4
 383 \fBpoll\fP(2)   2.2
 384 \fBppc_rtas\fP(2)               PowerPC only
 385 \fBppoll\fP(2)  2.6.16
 386 \fBprctl\fP(2)  2.2
 387 \fBpread64\fP(2)                T{
 388 Added as "pread" in 2.2; renamed "pread64" in 2.6
 389 T}
 390 \fBpreadv\fP(2) 2.6.30
 391 \fBprlimit\fP(2)        2.6.36
 392 \fBprocess_vm_readv\fP(2)       3.2
 393 \fBprocess_vm_writev\fP(2)      3.2
 394 \fBpselect6\fP(2)       2.6.16
 395 .\" Implements \fBpselect\fP(2)
 396 \fBptrace\fP(2)
 397 \fBpwrite64\fP(2)               T{
 398 Added as "pwrite" in 2.2; renamed "pwrite64" in 2.6
 399 T}
 400 \fBpwritev\fP(2)        2.6.30
 401 \fBquery_module\fP(2)   2.2     Removed in 2.6
 402 \fBquotactl\fP(2)
 403 \fBread\fP(2)
 404 \fBreadahead\fP(2)      2.4.13
 405 \fBreaddir\fP(2)
 406 .\" Supersedes \fBgetdents\fP(2)
 407 \fBreadlink\fP(2)
 408 \fBreadlinkat\fP(2)     2.6.16
 409 \fBreadv\fP(2)  2.0
 410 \fBreboot\fP(2)
 411 \fBrecv\fP(2)
 412 \fBrecvfrom\fP(2)
 413 \fBrecvmsg\fP(2)
 414 \fBrecvmmsg\fP(2)       2.6.33
 415 \fBremap_file_pages\fP(2)       2.6
 416 \fBremovexattr\fP(2)    2.6; 2.4.18
 417 \fBrename\fP(2)
 418 \fBrenameat\fP(2)       2.6.16
 419 \fBrequest_key\fP(2)    2.6.11
 420 \fBrestart_syscall\fP(2)        2.6
 421 \fBrmdir\fP(2)
 422 \fBrt_sigaction\fP(2)   2.2
 423 \fBrt_sigpending\fP(2)  2.2
 424 \fBrt_sigprocmask\fP(2) 2.2
 425 \fBrt_sigqueueinfo\fP(2)        2.2
 426 \fBrt_sigreturn\fP(2)   2.2
 427 \fBrt_sigsuspend\fP(2)  2.2
 428 \fBrt_sigtimedwait\fP(2)        2.2
 429 \fBrt_tgsigqueueinfo\fP(2)      2.6.31
 430 \fBs390_runtime_instr\fP(2)     3.7     s390 only
 431 \fBsched_get_priority_max\fP(2) 2.0
 432 \fBsched_get_priority_min\fP(2) 2.0
 433 \fBsched_getaffinity\fP(2)      2.6
 434 \fBsched_getparam\fP(2) 2.0
 435 \fBsched_getscheduler\fP(2)     2.0
 436 \fBsched_rr_get_interval\fP(2)  2.0
 437 \fBsched_setaffinity\fP(2)      2.6
 438 \fBsched_setparam\fP(2) 2.0
 439 \fBsched_setscheduler\fP(2)     2.0
 440 \fBsched_yield\fP(2)    2.0
 441 \fBselect\fP(2)
 442 \fBsemctl\fP(2)
 443 \fBsemget\fP(2)
 444 \fBsemop\fP(2)
 445 \fBsemtimedop\fP(2)     2.6; 2.4.22
 446 \fBsend\fP(2)
 447 \fBsendfile\fP(2)       2.2
 448 \fBsendfile64\fP(2)     2.6; 2.4.19
 449 \fBsendmmsg\fP(2)       3.0
 450 \fBsendmsg\fP(2)
 451 \fBsendto\fP(2)
 452 \fBset_mempolicy\fP(2)  2.6.6
 453 \fBset_robust_list\fP(2)        2.6.17
 454 \fBset_thread_area\fP(2)        2.6
 455 \fBset_tid_address\fP(2)        2.6
 456 .\" See http://lkml.org/lkml/2005/8/1/83
 457 .\" "[PATCH] remove sys_set_zone_reclaim()"
 458 \fBsetdomainname\fP(2)
 459 \fBsetfsgid\fP(2)       1.2
 460 \fBsetfsgid32\fP(2)     2.4
 461 \fBsetfsuid\fP(2)       1.2
 462 \fBsetfsuid32\fP(2)     2.4
 463 \fBsetgid\fP(2)
 464 \fBsetgid32\fP(2)       2.4
 465 \fBsetgroups\fP(2)
 466 \fBsetgroups32\fP(2)    2.4
 467 \fBsethostname\fP(2)
 468 \fBsetitimer\fP(2)
 469 \fBsetns\fP(2)  3.0
 470 \fBsetpgid\fP(2)
 471 \fBsetpriority\fP(2)
 472 \fBsetregid\fP(2)
 473 \fBsetregid32\fP(2)     2.4
 474 \fBsetresgid\fP(2)      2.2
 475 \fBsetresgid32\fP(2)    2.4
 476 \fBsetresuid\fP(2)      2.2
 477 \fBsetresuid32\fP(2)    2.4
 478 \fBsetreuid\fP(2)
 479 \fBsetreuid32\fP(2)     2.4
 480 \fBsetrlimit\fP(2)
 481 \fBsetsid\fP(2)
 482 \fBsetsockopt\fP(2)
 483 \fBsettimeofday\fP(2)
 484 \fBsetuid\fP(2)
 485 \fBsetuid32\fP(2)       2.4
 486 \fBsetup\fP(2)          Removed in 2.2
 487 \fBsetxattr\fP(2)       2.6; 2.4.18
 488 \fBsgetmask\fP(2)
 489 \fBshmat\fP(2)
 490 \fBshmctl\fP(2)
 491 \fBshmdt\fP(2)
 492 \fBshmget\fP(2)
 493 \fBshutdown\fP(2)
 494 \fBsigaction\fP(2)
 495 \fBsigaltstack\fP(2)    2.2
 496 \fBsignal\fP(2)
 497 \fBsignalfd\fP(2)       2.6.22
 498 \fBsignalfd4\fP(2)      2.6.27
 499 \fBsigpending\fP(2)
 500 \fBsigprocmask\fP(2)
 501 \fBsigreturn\fP(2)
 502 \fBsigsuspend\fP(2)
 503 \fBsocket\fP(2)
 504 \fBsocketcall\fP(2)
 505 .\" Implements BSD socket calls
 506 \fBsocketpair\fP(2)
 507 \fBsplice\fP(2) 2.6.17
 508 \fBspu_create\fP(2)     2.6.16  PowerPC only
 509 \fBspu_run\fP(2)        2.6.16  PowerPC only
 510 \fBssetmask\fP(2)
 511 \fBstat\fP(2)
 512 \fBstat64\fP(2) 2.4
 513 \fBstatfs\fP(2)
 514 \fBstatfs64\fP(2)       2.6
 515 \fBstime\fP(2)
 516 \fBsubpage_prot\fP(2)   2.6.25  PowerPC if
 517                 CONFIG_PPC_64K_PAGES
 518 \fBswapoff\fP(2)
 519 \fBswapon\fP(2)
 520 \fBsymlink\fP(2)
 521 \fBsymlinkat\fP(2)      2.6.16
 522 \fBsync\fP(2)
 523 \fBsync_file_range\fP(2)        2.6.17
 524 \fBsync_file_range2\fP(2)       2.6.22  T{
 525 Architecture-specific variant of \fBsync_file_range\fP(2)
 526 T}
 527 .\" PowerPC, ARM, tile
 528 .\" First appeared on ARM, as arm_sync_file_range(), but later renamed
 529 .\" \fBsys_debug_setcontext\fP(2)       ???     PowerPC if CONFIG_PPC32
 530 \fBsyncfs\fP(2) 2.6.39
 531 \fBsysfs\fP(2)  1.2
 532 \fBsysinfo\fP(2)
 533 \fBsyslog\fP(2)
 534 .\" glibc interface is \fBklogctl\fP(3)
 535 \fBtee\fP(2)    2.6.17
 536 \fBtgkill\fP(2) 2.6
 537 \fBtime\fP(2)
 538 \fBtimer_create\fP(2)   2.6
 539 \fBtimer_delete\fP(2)   2.6
 540 \fBtimer_getoverrun\fP(2)       2.6
 541 \fBtimer_gettime\fP(2)  2.6
 542 \fBtimer_settime\fP(2)  2.6
 543 \fBtimerfd_create\fP(2) 2.6.25
 544 \fBtimerfd_gettime\fP(2)        2.6.25
 545 \fBtimerfd_settime\fP(2)        2.6.25
 546 \fBtimes\fP(2)
 547 \fBtkill\fP(2)  2.6; 2.4.22
 548 \fBtruncate\fP(2)
 549 \fBtruncate64\fP(2)     2.4
 550 \fBugetrlimit\fP(2)     2.4
 551 \fBumask\fP(2)
 552 \fBumount\fP(2)
 553 .\" sys_oldumount() -- __NR_umount
 554 \fBumount2\fP(2)        2.2
 555 .\" sys_umount() -- __NR_umount2
 556 \fBuname\fP(2)
 557 \fBunlink\fP(2)
 558 \fBunlinkat\fP(2)       2.6.16
 559 \fBunshare\fP(2)        2.6.16
 560 \fBuselib\fP(2)
 561 \fBustat\fP(2)
 562 \fButime\fP(2)
 563 \fButimensat\fP(2)      2.6.22
 564 \fButimes\fP(2) 2.2
 565 \fButrap_install\fP(2)  2.2     Sparc
 566 \fBvfork\fP(2)
 567 \fBvhangup\fP(2)
 568 \fBvm86old\fP(2)
 569 .\" Superseded by \fBvm86\fP(2)
 570 \fBvmsplice\fP(2)       2.6.17
 571 \fBwait4\fP(2)
 572 \fBwaitid\fP(2) 2.6.10
 573 \fBwaitpid\fP(2)
 574 \fBwrite\fP(2)
 575 \fBwritev\fP(2) 2.0
 576 .TE
 577 .ad
 578 .PP
 579 On many platforms, including x86-32, socket calls are all multiplexed
 580 (via glibc wrapper functions) through
 581 .BR socketcall (2)
 582 and similarly System V IPC calls are multiplexed through
 583 .BR ipc (2).
 584
 585 Although slots are reserved for them in the system call table,
 586 the following system calls are not implemented in the standard kernel:
 587 .BR afs_syscall (2), \" __NR_afs_syscall is 53 on Linux 2.6.22/i386
 588 .BR break (2),       \" __NR_break is 17 on Linux 2.6.22/i386
 589 .BR ftime (2),       \" __NR_ftime is 35 on Linux 2.6.22/i386
 590 .BR getpmsg (2),     \" __NR_getpmsg is 188 on Linux 2.6.22/i386
 591 .BR gtty (2),        \" __NR_gtty is 32 on Linux 2.6.22/i386
 592 .BR idle (2),        \" __NR_idle is 112 on Linux 2.6.22/i386
 593 .BR lock (2),        \" __NR_lock is 53 on Linux 2.6.22/i386
 594 .BR madvise1 (2),    \" __NR_madvise1 is 219 on Linux 2.6.22/i386
 595 .BR mpx (2),         \" __NR_mpx is 66 on Linux 2.6.22/i386
 596 .BR phys (2),        \" Slot has been reused
 597 .BR prof (2),        \" __NR_prof is 44 on Linux 2.6.22/i386
 598 .BR profil (2),      \" __NR_profil is 98 on Linux 2.6.22/i386
 599 .BR putpmsg (2),     \" __NR_putpmsg is 189 on Linux 2.6.22/i386
 600 .\" __NR_security is 223 on Linux 2.4/i386; absent on 2.6/i386, present
 601 .\" on a couple of 2.6 architectures
 602 .BR security (2),    \" __NR_security is 223 on Linux 2.4/i386
 603 .\" The security call is for future use.
 604 .BR stty (2),        \" __NR_stty is 31 on Linux 2.6.22/i386
 605 .BR tuxcall (2),     \" __NR_tuxcall is 184 on x86_64, also on PPC and alpha
 606 .BR ulimit (2),      \" __NR_ulimit is 58 on Linux 2.6.22/i386
 607 and
 608 .BR vserver (2)      \" __NR_vserver is 273 on Linux 2.6.22/i386
 609 (see also
 610 .BR unimplemented (2)).
 611 However,
 612 .BR ftime (3),
 613 .BR profil (3)
 614 and
 615 .BR ulimit (3)
 616 exist as library routines.
 617 The slot for
 618 .BR phys (2)
 619 is in use since kernel 2.1.116 for
 620 .BR umount (2);
 621 .BR phys (2)
 622 will never be implemented.
 623 The
 624 .BR getpmsg (2)
 625 and
 626 .BR putpmsg (2)
 627 calls are for kernels patched to support STREAMS,
 628 and may never be in the standard kernel.
 629
 630 There was briefly
 631 .BR set_zone_reclaim (2),
 632 added in Linux 2.6.13, and removed in 2.6.16;
 633 this system call was never available to user space.
 634 .SH NOTES
 635 .PP
 636 Roughly speaking, the code belonging to the system call
 637 with number __NR_xxx defined in
 638 .I /usr/include/asm/unistd.h
 639 can be found in the Linux kernel source in the routine
 640 .IR sys_xxx ().
 641 (The dispatch table for i386 can be found in
 642 .IR /usr/src/linux/arch/i386/kernel/entry.S .)
 643 There are many exceptions, however, mostly because
 644 older system calls were superseded by newer ones,
 645 and this has been treated somewhat unsystematically.
 646 On platforms with
 647 proprietary operating-system emulation,
 648 such as parisc, sparc, sparc64 and alpha,
 649 there are many additional system calls; mips64 also contains a full
 650 set of 32-bit system calls.
 651
 652 Over time, changes to the interfaces of some system calls have been
 653 necessary.
 654 One reason for such changes was the need to increase the size of
 655 structures or scalar values passed to the system call.
 656 Because of these changes, there are now various groups
 657 of related system calls
 658 (e.g.,
 659 .BR truncate (2)
 660 and
 661 .BR truncate64 (2))
 662 which perform similar tasks, but which vary in
 663 details such as the size of their arguments.
 664 (As noted earlier, applications are generally unaware of this:
 665 the glibc wrapper functions do some work to ensure that the right
 666 system call is invoked, and that ABI compatibility is
 667 preserved for old binaries.)
 668 Examples of systems calls that exist in multiple versions are
 669 the following:
 670 .IP * 3
 671 By now there are three different versions of
 672 .BR stat (2):
 673 .IR sys_stat ()
 674 (slot
 675 .IR __NR_oldstat ),
 676 .IR sys_newstat ()
 677 (slot
 678 .IR __NR_stat ),
 679 and
 680 .IR sys_stat64 ()
 681 (slot
 682 .IR __NR_stat64 ),
 683 with the last being the most current.
 684 .\" e.g., on 2.6.22/i386: __NR_oldstat 18, __NR_stat 106, __NR_stat64 195
 685 .\" The stat system calls deal with three different data structures,
 686 .\" defined in include/asm-i386/stat.h: __old_kernel_stat, stat, stat64
 687 A similar story applies for
 688 .BR lstat (2)
 689 and
 690 .BR fstat (2).
 691 .IP *
 692 Similarly, the defines
 693 .IR __NR_oldolduname ,
 694 .IR __NR_olduname ,
 695 and
 696 .I __NR_uname
 697 refer to the routines
 698 .IR sys_olduname (),
 699 .IR sys_uname ()
 700 and
 701 .IR sys_newuname ().
 702 .IP *
 703 In Linux 2.0, a new version of
 704 .BR vm86 (2)
 705 appeared, with the old and the new kernel routines being named
 706 .IR sys_vm86old ()
 707 and
 708 .IR sys_vm86 ().
 709 .IP *
 710 In Linux 2.4, a new version of
 711 .BR getrlimit (2)
 712 appeared, with the old and the new kernel routines being named
 713 .IR sys_old_getrlimit ()
 714 (slot
 715 .IR __NR_getrlimit )
 716 and
 717 .IR sys_getrlimit ()
 718 (slot
 719 .IR __NR_ugetrlimit ).
 720 .IP *
 721 Linux 2.4 increased the size of user and group IDs from 16 to 32 bits.
 722 .\" 64-bit off_t changes: ftruncate64, *stat64,
 723 .\" fcntl64 (because of the flock structure), getdents64, *statfs64
 724 To support this change, a range of system calls were added
 725 (e.g.,
 726 .BR chown32 (2),
 727 .BR getuid32 (2),
 728 .BR getgroups32 (2),
 729 .BR setresuid32 (2)),
 730 superseding earlier calls of the same name without the
 731 "32" suffix.
 732 .IP *
 733 Linux 2.4 added support for applications on 32-bit architectures
 734 to access large files (i.e., files for which the sizes and
 735 file offsets can't be represented in 32 bits.)
 736 To support this change, replacements were required for system calls
 737 that deal with file offsets and sizes.
 738 Thus the following system calls were added:
 739 .BR fcntl64 (2),
 740 .BR ftruncate64 (2),
 741 .BR getdents64 (2),
 742 .BR stat64 (2),
 743 .BR statfs64 (2),
 744 and their analogs that work with file descriptors or
 745 symbolic links.
 746 These system calls supersede the older system calls
 747 which, except in the case of the "stat" calls,
 748 have the same name without the "64" suffix.
 749
 750 On newer platforms that only have 64-bit file access and 32-bit uids
 751 (e.g., alpha, ia64, s390x) there are no *64 or *32 calls.
 752 Where the *64 and *32 calls exist, the other versions are obsolete.
 753 .IP *
 754 The
 755 .I rt_sig*
 756 calls were added in kernel 2.2 to support the addition
 757 of real-time signals (see
 758 .BR signal (7)).
 759 These system calls supersede the older system calls of the same
 760 name without the "rt_" prefix.
 761 .IP *
 762 The
 763 .BR select (2)
 764 and
 765 .BR mmap (2)
 766 system calls use five or more arguments,
 767 which caused problems in the way
 768 argument passing on the i386 used to be set up.
 769 Thus, while other architectures have
 770 .IR sys_select ()
 771 and
 772 .IR sys_mmap ()
 773 corresponding to
 774 .I __NR_select
 775 and
 776 .IR __NR_mmap ,
 777 on i386 one finds
 778 .IR old_select ()
 779 and
 780 .IR old_mmap ()
 781 (routines that use a pointer to a
 782 argument block) instead.
 783 These days passing five arguments
 784 is not a problem any more, and there is a
 785 .I __NR__newselect
 786 .\" (used by libc 6)
 787 that corresponds directly to
 788 .IR sys_select ()
 789 and similarly
 790 .IR __NR_mmap2 .
 791 .\" .PP
 792 .\" Two system call numbers,
 793 .\" .IR __NR__llseek
 794 .\" and
 795 .\" .IR __NR__sysctl
 796 .\" have an additional underscore absent in
 797 .\" .IR sys_llseek ()
 798 .\" and
 799 .\" .IR sys_sysctl ().
 800 .\"
 801 .\" In kernel 2.1.81,
 802 .\" .BR lchown (2)
 803 .\" and
 804 .\" .BR chown (2)
 805 .\" were swapped; that is,
 806 .\" .BR lchown (2)
 807 .\" was added with the semantics that were then current for
 808 .\" .BR chown (2),
 809 .\" and the semantics of the latter call were changed to what
 810 .\" they are today.
 811 .SH SEE ALSO
 812 .BR syscall (2),
 813 .BR unimplemented (2),
 814 .BR libc (7)