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>
   8 .\"
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  13 .\" Permission is granted to copy and distribute modified versions of this
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  28 .\"
  29 .TH SYSCALLS 2 2007-09-01 "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 before invoking the system call.
  50
  51 Sometimes, however, the wrapper function does some extra work
  52 before invoking the system call.
  53 For example, nowadays there are (for reasons described below) two
  54 related system calls,
  55 .BR truncate (2)
  56 and
  57 .BR truncate64 (2),
  58 and the glibc
  59 .BR truncate ()
  60 wrapper function checks which of those system calls
  61 are provided by the kernel and determines which should be employed.
  62 .SS System call list
  63 Below is a list of those system calls that are common to most platforms.
  64 In the list, the
  65 .I Kernel
  66 column indicates the kernel version
  67 for those system calls that were new in Linux 2.2,
  68 or have appeared since that kernel version.
  69 Note the following points:
  70 .IP * 3
  71 Where no kernel version is indicated,
  72 the system call appeared in kernel 2.0 or earlier.
  73 .\" kernel 1.2 was started from a branch of 1.0.6
  74 .\"
  75 .\" Was kernel 2.0 started from a branch of 1.2.10?
  76 .\" At least from the timestamps of the tarballs of
  77 .\" of 1.2.10 and 1.3.0, that's how it looks, but in
  78 .\" fact the diff doesn't seem very clear, the
  79 .\" 1.3.0 .tar.bz is much bigger (2.0 MB) than the
  80 .\" 1.2.10 .tar.bz2 (1.8 MB), and AEB points out the
  81 .\" timestamps of some files in 1.3.0 seem to be older
  82 .\" than those in 1.2.10.  All of this suggests
  83 .\" that there might not have been a clean branch point.
  84 .IP *
  85 Where a system call is marked "2.2"
  86 this means the system call probably appeared in a 2.1.x kernel version,
  87 and first appeared in a stable kernel with 2.2.0.
  88 (Development of the 2.2 kernel was initiated from a branch of kernel
  89 2.0.21 via the 2.1.x unstable kernel series.)
  90 .IP *
  91 Where a system call is marked "2.4"
  92 this means the system call probably appeared in a 2.3.x kernel version,
  93 and first appeared in a stable kernel with 2.4.0.
  94 (Development of the 2.4 kernel was initiated from a branch of
  95 kernel 2.2.8 via the 2.3.x unstable kernel series.)
  96 .IP *
  97 Where a system call is marked "2.6"
  98 this means the system call probably appeared in a 2.5.x kernel version,
  99 and first appeared in a stable kernel with 2.6.0.
 100 (Development of kernel 2.6 was initiated from a branch
 101 of kernel 2.4.15 via the 2.5.x unstable kernel series.)
 102 .IP *
 103 Starting with kernel 2.6.0, the development model changed,
 104 and new system calls may appear in each 2.6.x release.
 105 In this case, the exact version number where the system call appeared
 106 is shown.
 107 .IP *
 108 In some cases, a system call was added to a stable kernel
 109 series after it branched from the previous stable kernel
 110 series, and then backported into the earlier stable kernel series.
 111 For example some system calls that appeared in 2.6.x were also backported
 112 into a 2.4.x release after 2.4.15.
 113 When this is so, the version where the system call appeared
 114 in both of the major kernel series is listed.
 115 .PP
 116 The list of system calls that are available as at kernel 2.6.22
 117 (or in a few cases only on older kernels) is as follows:
 118 .\"
 119 .\" Looking at scripts/checksyscalls.sh in the kernel source is
 120 .\" instructive about i386 specifics.
 121 .\"
 122 .TS
 123 l l l
 124 ---
 125 l l l.
 126 \fBSystem call\fP       \fBKernel\fP    \fBNotes\fP
 127
 128 \fB_llseek\fP(2)
 129 \fB_newselect\fP(2)
 130 \fB_sysctl\fP(2)
 131 \fBaccept\fP(2)
 132 \fBaccess\fP(2)
 133 \fBacct\fP(2)
 134 \fBadd_key\fP(2)        2.6.11
 135 \fBadjtimex\fP(2)
 136 \fBafs_syscall\fP(2)
 137 \fBalarm\fP(2)
 138 \fBalloc_hugepages\fP(2)        2.5.36  Removed in 2.5.44
 139 \fBbdflush\fP(2)
 140 \fBbind\fP(2)
 141 \fBbreak\fP(2)
 142 \fBbrk\fP(2)
 143 \fBcacheflush\fP(2)             Not on i386
 144 \fBcapget\fP(2) 2.2
 145 \fBcapset\fP(2) 2.2
 146 \fBchdir\fP(2)
 147 \fBchmod\fP(2)
 148 \fBchown\fP(2)
 149 \fBchown32\fP(2)        2.4
 150 \fBchroot\fP(2)
 151 \fBclock_getres\fP(2)   2.6
 152 \fBclock_gettime\fP(2)  2.6
 153 \fBclock_nanosleep\fP(2)        2.6
 154 \fBclock_settime\fP(2)  2.6
 155 \fBclone\fP(2)
 156 \fBclose\fP(2)
 157 \fBconnect\fP(2)
 158 \fBcreat\fP(2)
 159 \fBcreate_module\fP(2)
 160 \fBdelete_module\fP(2)
 161 \fBdup\fP(2)
 162 \fBdup2\fP(2)
 163 \fBepoll_create\fP(2)   2.6
 164 \fBepoll_ctl\fP(2)      2.6
 165 \fBepoll_pwait\fP(2)    2.6.19
 166 \fBepoll_wait\fP(2)     2.6
 167 \fBeventfd\fP(2)        2.6.22
 168 \fBexecve\fP(2)
 169 \fBexit\fP(2)
 170 \fBexit_group\fP(2)     2.6; 2.4.20
 171 \fBfaccessat\fP(2)      2.6.16
 172 \fBfadvise64\fP(2)      2.6
 173 .\" Implements \fBposix_fadvise\fP(2)
 174 \fBfadvise64_64\fP(2)   2.6
 175 .\" FIXME \fBfallocate\fP(2)    2.6.23
 176 \fBfchdir\fP(2)
 177 \fBfchmod\fP(2)
 178 \fBfchmodat\fP(2)       2.6.16
 179 \fBfchown\fP(2)
 180 \fBfchown32\fP(2)       2.4
 181 \fBfchownat\fP(2)       2.6.16
 182 \fBfcntl\fP(2)
 183 \fBfcntl64\fP(2)        2.4
 184 \fBfdatasync\fP(2)
 185 \fBfgetxattr\fP(2)      2.6; 2.4.18
 186 \fBflistxattr\fP(2)     2.6; 2.4.18
 187 \fBflock\fP(2)
 188 \fBfork\fP(2)
 189 \fBfree_hugepages\fP(2) 2.5.36  Removed in 2.5.44
 190 \fBfremovexattr\fP(2)   2.6; 2.4.18
 191 \fBfsetxattr\fP(2)      2.6; 2.4.18
 192 \fBfstat\fP(2)
 193 \fBfstat64\fP(2)        2.4
 194 \fBfstatat64\fP(2)      2.6.16
 195 \fBfstatfs\fP(2)
 196 \fBfstatfs64\fP(2)      2.6
 197 \fBfsync\fP(2)
 198 \fBftime\fP(2)
 199 .\" Implemented in glibc; see \fBftime\fP(3)
 200 \fBftruncate\fP(2)
 201 \fBftruncate64\fP(2)    2.4
 202 \fBfutex\fP(2)  2.6; 2.4.19
 203 \fBfutimesat\fP(2)      2.6.16
 204 \fBget_kernel_syms\fP(2)
 205 \fBget_mempolicy\fP(2)  2.6.6
 206 \fBget_robust_list\fP(2)        2.6.17
 207 \fBget_thread_area\fP(2)        2.6; 2.4.20
 208 \fBgetcpu\fP(2) 2.6.19
 209 \fBgetcwd\fP(2) 2.2
 210 \fBgetdents\fP(2)
 211 \fBgetdents64\fP(2)     2.4
 212 \fBgetegid\fP(2)
 213 \fBgetegid32\fP(2)      2.4
 214 \fBgeteuid\fP(2)
 215 \fBgeteuid32\fP(2)      2.4
 216 \fBgetgid\fP(2)
 217 \fBgetgid32\fP(2)       2.4
 218 \fBgetgroups\fP(2)
 219 \fBgetgroups32\fP(2)    2.4
 220 \fBgetitimer\fP(2)
 221 \fBgetpeername\fP(2)
 222 \fBgetpagesize\fP(2)            Not on i386
 223 \fBgetpgid\fP(2)
 224 \fBgetpgrp\fP(2)
 225 \fBgetpid\fP(2)
 226 \fBgetpmsg\fP(2)        2.2
 227 .\" Reserved for STREAMS support
 228 \fBgetppid\fP(2)
 229 \fBgetpriority\fP(2)
 230 \fBgetresgid\fP(2)      2.2
 231 \fBgetresgid32\fP(2)    2.4
 232 \fBgetresuid\fP(2)      2.2
 233 \fBgetresuid32\fP(2)    2.4
 234 \fBgetrlimit\fP(2)
 235 \fBgetrusage\fP(2)
 236 \fBgetsid\fP(2)
 237 \fBgetsockname\fP(2)
 238 \fBgetsockopt\fP(2)
 239 \fBgettid\fP(2) 2.4.11
 240 \fBgettimeofday\fP(2)
 241 \fBgetuid\fP(2)
 242 \fBgetuid32\fP(2)       2.4
 243 \fBgetxattr\fP(2)       2.6; 2.4.18
 244 .\" \fBgetunwind\fP(2)  ???     ia64; DEPRECATED
 245 \fBgtty\fP(2)
 246 \fBidle\fP(2)
 247 \fBinit_module\fP(2)
 248 \fBinotify_add_watch\fP(2)      2.6.13
 249 \fBinotify_init\fP(2)   2.6.13
 250 \fBinotify_rm_watch\fP(2)       2.6.13
 251 \fBio_cancel\fP(2)      2.6; 2.4.20
 252 \fBio_destroy\fP(2)     2.6; 2.4.20
 253 \fBio_getevents\fP(2)   2.6; 2.4.20
 254 \fBio_setup\fP(2)       2.6; 2.4.20
 255 \fBio_submit\fP(2)      2.6; 2.4.20
 256 \fBioctl\fP(2)
 257 \fBioperm\fP(2)
 258 \fBiopl\fP(2)
 259 \fBioprio_get\fP(2)     2.6.13
 260 \fBioprio_set\fP(2)     2.6.13
 261 \fBipc\fP(2)
 262 .\" Implements System V IPC calls
 263 \fBkexec_load\fP(2)     2.6.7
 264 .\" Was named sys_kexec_load() from 2.6.7 to 2.6.16
 265 \fBkeyctl\fP(2) 2.6.11
 266 \fBkill\fP(2)
 267 \fBlchown\fP(2) 2.2
 268 \fBlchown32\fP(2)       2.4
 269 \fBlgetxattr\fP(2)      2.6; 2.4.18
 270 \fBlink\fP(2)
 271 \fBlinkat\fP(2) 2.6.16
 272 \fBlisten\fP(2)
 273 \fBlistxattr\fP(2)      2.6; 2.4.18
 274 \fBllistxattr\fP(2)     2.6; 2.4.18
 275 \fBlock\fP(2)
 276 \fBlookup_dcookie\fP(2) 2.6
 277 \fBlremovexattr\fP(2)   2.6; 2.4.18
 278 \fBlseek\fP(2)
 279 \fBlsetxattr\fP(2)      2.6; 2.4.18
 280 \fBlstat\fP(2)
 281 \fBlstat64\fP(2)        2.4
 282 \fBmadvise\fP(2)        2.4
 283 \fBmadvise1\fP(2)       2.4
 284 \fBmbind\fP(2)  2.6.6
 285 .\" \fBmemory_ordering\fP(2)    ???     Sparc64
 286 \fBmigrate_pages\fP(2)  2.6.16
 287 \fBmincore\fP(2)        2.4
 288 \fBmkdir\fP(2)
 289 \fBmkdirat\fP(2)        2.6.16
 290 \fBmknod\fP(2)
 291 \fBmknodat\fP(2)        2.6.16
 292 \fBmlock\fP(2)
 293 \fBmlockall\fP(2)
 294 \fBmmap\fP(2)
 295 \fBmmap2\fP(2)  2.4
 296 \fBmodify_ldt\fP(2)
 297 \fBmount\fP(2)
 298 \fBmove_pages\fP(2)     2.6.18
 299 \fBmprotect\fP(2)
 300 \fBmpx\fP(2)
 301 \fBmq_getsetattr\fP(2)  2.6.6
 302 .\" Implements \fBmq_getattr\fP(3) and \fBmq_setattr\fP(3)
 303 \fBmq_notify\fP(2)      2.6.6
 304 \fBmq_open\fP(2)        2.6.6
 305 \fBmq_timedreceive\fP(2)        2.6.6
 306 \fBmq_timedsend\fP(2)   2.6.6
 307 \fBmq_unlink\fP(2)
 308 \fBmremap\fP(2)
 309 \fBmsgctl\fP(2)
 310 \fBmsgget\fP(2)
 311 \fBmsgrcv\fP(2)
 312 \fBmsgsnd\fP(2)
 313 \fBmsync\fP(2)
 314 .\" \fBmultiplexer\fP(2)        ??      __NR_multiplexer reserved on
 315 .\"             PowerPC, but unimplemented?
 316 \fBmunlock\fP(2)
 317 \fBmunlockall\fP(2)
 318 \fBmunmap\fP(2)
 319 \fBnanosleep\fP(2)
 320 \fBnfsservctl\fP(2)     2.2
 321 \fBnice\fP(2)
 322 \fBoldfstat\fP(2)
 323 \fBoldlstat\fP(2)
 324 \fBoldolduname\fP(2)
 325 \fBoldstat\fP(2)
 326 \fBolduname\fP(2)
 327 \fBopen\fP(2)
 328 \fBopenat\fP(2) 2.6.16
 329 \fBpause\fP(2)
 330 \fBpciconfig_iobase\fP(2)       2.2.15; 2.4     Not on i386
 331 .\" Alpha, PowerPC, ARM; not i386
 332 \fBpciconfig_read\fP(2) 2.0.26; 2.2     Not on i386
 333 .\" , PowerPC, ARM; not i386
 334 \fBpciconfig_write\fP(2)        2.0.26; 2.2     Not on i386
 335 .\" , PowerPC, ARM; not i386
 336 \fBpersonality\fP(2)
 337 .\" \fBperfctr\fP(2)    ???     Sparc32, Sparc64
 338 .\" \fBperfmonctl\fP(2) ???     ia64
 339 \fBphys\fP(2)
 340 .\" Unimplemented (no slot since 2.1.116)
 341 \fBpipe\fP(2)
 342 \fBpivot_root\fP(2)     2.5
 343 \fBpoll\fP(2)   2.2
 344 \fBppoll\fP(2)  2.6.16
 345 \fBprctl\fP(2)  2.2
 346 \fBpread64\fP(2)                Added as "pread" in 2.2;
 347                 renamed "pread64" in 2.6
 348 \fBprof\fP(2)
 349 \fBprofil\fP(2)
 350 .\" Implemented in glibc; see \fBprofil\fP(3)
 351 \fBpselect6\fP(2)       2.6.16
 352 .\" Implements \fBpselect\fP(2)
 353 \fBptrace\fP(2)
 354 \fBputpmsg\fP(2)        2.2
 355 .\" Reserved for STREAMS support
 356 \fBpwrite64\fP(2)               Added as "pwrite" in 2.2;
 357                 renamed "pwrite64" in 2.6
 358 \fBquery_module\fP(2)   2.2
 359 \fBquotactl\fP(2)
 360 \fBread\fP(2)
 361 \fBreadahead\fP(2)      2.4.13
 362 \fBreaddir\fP(2)
 363 .\" Supersedes \fBgetdents\fP(2)
 364 \fBreadlink\fP(2)
 365 \fBreadlinkat\fP(2)     2.6.16
 366 \fBreadv\fP(2)
 367 \fBreboot\fP(2)
 368 \fBrecv\fP(2)
 369 \fBrecvfrom\fP(2)
 370 \fBrecvmsg\fP(2)
 371 \fBremap_file_pages\fP(2)       2.6
 372 \fBremovexattr\fP(2)    2.6; 2.4.18
 373 \fBrename\fP(2)
 374 \fBrenameat\fP(2)       2.6.16
 375 \fBrequest_key\fP(2)    2.6.11
 376 \fBrestart_syscall\fP(2)        2.6
 377 \fBrmdir\fP(2)
 378 \fBrt_sigaction\fP(2)   2.2
 379 \fBrt_sigpending\fP(2)  2.2
 380 \fBrt_sigprocmask\fP(2) 2.2
 381 \fBrt_sigqueueinfo\fP(2)        2.2
 382 .\" Implements \fBsigqueue\fP(2)
 383 \fBrt_sigreturn\fP(2)   2.2
 384 \fBrt_sigsuspend\fP(2)  2.2
 385 \fBrt_sigtimedwait\fP(2)        2.2
 386 \fBsched_get_priority_max\fP(2)
 387 \fBsched_get_priority_min\fP(2)
 388 \fBsched_getaffinity\fP(2)      2.6; 2.4.19
 389 \fBsched_getparam\fP(2)
 390 \fBsched_getscheduler\fP(2)
 391 \fBsched_rr_get_interval\fP(2)
 392 \fBsched_setaffinity\fP(2)      2.6; 2.4.19
 393 \fBsched_setparam\fP(2)
 394 \fBsched_setscheduler\fP(2)
 395 \fBsched_yield\fP(2)
 396 \fBsecurity\fP(2)       2.4.11
 397 \fBselect\fP(2)
 398 \fBsemctl\fP(2)
 399 \fBsemget\fP(2)
 400 \fBsemop\fP(2)
 401 \fBsemtimedop\fP(2)     2.6; 2.4.22
 402 \fBsend\fP(2)
 403 \fBsendfile\fP(2)       2.2
 404 \fBsendfile64\fP(2)     2.6; 2.4.19
 405 \fBsendmsg\fP(2)
 406 \fBsendto\fP(2)
 407 \fBset_mempolicy\fP(2)  2.6.6
 408 \fBset_robust_list\fP(2)        2.6.17
 409 \fBset_thread_area\fP(2)        2.6; 2.4.20
 410 \fBset_tid_address\fP(2)        2.6
 411 \fBset_zone_reclaim\fP(2)       2.6.13  Removed in 2.6.16 (was never
 412                 available to userspace)
 413 .\" See http://lkml.org/lkml/2005/8/1/83
 414 .\" "[PATCH] remove sys_set_zone_reclaim()"
 415 \fBsetdomainname\fP(2)
 416 \fBsetfsgid\fP(2)
 417 \fBsetfsgid32\fP(2)     2.4
 418 \fBsetfsuid\fP(2)
 419 \fBsetfsuid32\fP(2)     2.4
 420 \fBsetgid\fP(2)
 421 \fBsetgid32\fP(2)       2.4
 422 \fBsetgroups\fP(2)
 423 \fBsetgroups32\fP(2)    2.4
 424 \fBsethostname\fP(2)
 425 \fBsetitimer\fP(2)
 426 \fBsetpgid\fP(2)
 427 \fBsetpriority\fP(2)
 428 \fBsetregid\fP(2)
 429 \fBsetregid32\fP(2)     2.4
 430 \fBsetresgid\fP(2)      2.2
 431 \fBsetresgid32\fP(2)    2.4
 432 \fBsetresuid\fP(2)      2.2
 433 \fBsetresuid32\fP(2)    2.4
 434 \fBsetreuid\fP(2)
 435 \fBsetreuid32\fP(2)     2.4
 436 \fBsetrlimit\fP(2)
 437 \fBsetsid\fP(2)
 438 \fBsetsockopt\fP(2)
 439 \fBsettimeofday\fP(2)
 440 \fBsetuid\fP(2)
 441 \fBsetuid32\fP(2)       2.4
 442 \fBsetup\fP(2)          Removed in 2.2
 443 \fBsetxattr\fP(2)       2.6; 2.4.18
 444 \fBsgetmask\fP(2)
 445 \fBshmat\fP(2)
 446 \fBshmctl\fP(2)
 447 \fBshmdt\fP(2)
 448 \fBshmget\fP(2)
 449 \fBshutdown\fP(2)
 450 \fBsigaction\fP(2)
 451 \fBsigaltstack\fP(2)    2.2
 452 \fBsignal\fP(2)
 453 \fBsignalfd\fP(2)       2.6.22
 454 \fBsigpending\fP(2)
 455 \fBsigprocmask\fP(2)
 456 \fBsigreturn\fP(2)
 457 \fBsigsuspend\fP(2)
 458 \fBsocket\fP(2)
 459 \fBsocketcall\fP(2)
 460 .\" Implements BSD socket calls
 461 \fBsocketpair\fP(2)
 462 \fBsplice\fP(2) 2.6.17
 463 \fBspu_create\fP(2)     2.6.16  PowerPC only
 464 \fBspu_run\fP(2)        2.6.16  PowerPC only
 465 \fBssetmask\fP(2)
 466 \fBstat\fP(2)
 467 \fBstat64\fP(2) 2.4
 468 \fBstatfs\fP(2)
 469 \fBstatfs64\fP(2)       2.6
 470 \fBstime\fP(2)
 471 \fBstty\fP(2)
 472 \fBswapoff\fP(2)
 473 \fBswapon\fP(2)
 474 \fBsymlink\fP(2)
 475 \fBsymlinkat\fP(2)      2.6.16
 476 \fBsync\fP(2)
 477 \fBsync_file_range\fP(2)        2.6.17
 478 .\" \fBsys_debug_setcontext\fP(2)       ???     PowerPC if CONFIG_PPC32
 479 \fBsysfs\fP(2)
 480 \fBsysinfo\fP(2)
 481 \fBsyslog\fP(2)
 482 .\" glibc interface is \fBklogctl\fP(3)
 483 \fBtee\fP(2)    2.6.17
 484 \fBtgkill\fP(2) 2.6
 485 \fBtime\fP(2)
 486 \fBtimer_create\fP(2)   2.6
 487 \fBtimer_delete\fP(2)   2.6
 488 \fBtimer_getoverrun\fP(2)       2.6
 489 \fBtimer_gettime\fP(2)  2.6
 490 \fBtimer_settime\fP(2)  2.6
 491 \fBtimerfd\fP(2)        2.6.22
 492 \fBtimes\fP(2)
 493 \fBtkill\fP(2)  2.6; 2.4.22
 494 \fBtruncate\fP(2)
 495 \fBtruncate64\fP(2)     2.4
 496 \fBtuxcall\fP(2)
 497 .\" Unimplemented; no slot on i386
 498 .\" As at 2.6.22, tuxcall has a slot on PowerPC, x86_64, and alpha
 499 \fBugetrlimit\fP(2)     2.4
 500 \fBulimit\fP(2)
 501 .\" Implemented in glibc; see \fBulimit\fP(3)
 502 \fBumask\fP(2)
 503 \fBumount\fP(2)
 504 .\" sys_oldumount() -- __NR_umount
 505 \fBumount2\fP(2)        2.2
 506 .\" sys_umount() -- __NR_umount2
 507 \fBuname\fP(2)
 508 \fBunlink\fP(2)
 509 \fBunlinkat\fP(2)       2.6.16
 510 \fBunshare\fP(2)        2.6.16
 511 \fBuselib\fP(2)
 512 \fBustat\fP(2)
 513 \fButime\fP(2)
 514 \fButimensat\fP(2)      2.6.22
 515 \fButimes\fP(2) 2.6
 516 \fBvfork\fP(2)
 517 \fBvhangup\fP(2)
 518 \fBvm86old\fP(2)
 519 .\" Superseded by \fBvm86\fP(2)
 520 \fBvmsplice\fP(2)       2.6.17
 521 \fBvserver\fP(2)        2.6
 522 \fBwait4\fP(2)
 523 \fBwaitid\fP(2) 2.6.10
 524 \fBwaitpid\fP(2)
 525 \fBwrite\fP(2)
 526 \fBwritev\fP(2)
 527 .TE
 528 .PP
 529 On many platforms, including i386, socket calls are all multiplexed
 530 (via glibc wrapper functions) through
 531 .BR socketcall (2)
 532 and similarly System V IPC calls are multiplexed through
 533 .BR ipc (2).
 534 .SH NOTES
 535 Note the following points:
 536 .IP * 3
 537 Although slots are reserved for them in the system call table,
 538 the following system calls are not implemented in the standard kernel:
 539 .BR afs_syscall (2), \" __NR_afs_syscall is 53 on Linux 2.6.22/i386
 540 .BR break (2),       \" __NR_break is 17 on Linux 2.6.22/i386
 541 .BR ftime (2),       \" __NR_ftime is 35 on Linux 2.6.22/i386
 542 .BR getpmsg (2),     \" __NR_getpmsg is 188 on Linux 2.6.22/i386
 543 .BR gtty (2),        \" __NR_gtty is 32 on Linux 2.6.22/i386
 544 .BR idle (2),        \" __NR_idle is 112 on Linux 2.6.22/i386
 545 .BR lock (2),        \" __NR_lock is 53 on Linux 2.6.22/i386
 546 .BR madvise1 (2),    \" __NR_madvise1 is 219 on Linux 2.6.22/i386
 547 .BR mpx (2),         \" __NR_mpx is 66 on Linux 2.6.22/i386
 548 .BR phys (2),        \" Slot has been re-used
 549 .BR prof (2),        \" __NR_prof is 44 on Linux 2.6.22/i386
 550 .BR profil (2),      \" __NR_profil is 98 on Linux 2.6.22/i386
 551 .BR putpmsg (2),     \" __NR_putpmsg is 189 on Linux 2.6.22/i386
 552 .\" __NR_security is 223 on Linux 2.4/i386; absent on 2.6/i386, present
 553 .\" on a couple of 2.6 architectures
 554 .BR security (2),    \" __NR_security is 223 on Linux 2.4/i386
 555 .BR stty (2),        \" __NR_stty is 31 on Linux 2.6.22/i386
 556 .BR tuxcall (2),     \" __NR_tuxcall is 184 on x86_64, also on PPC and alpha
 557 .BR ulimit (2),      \" __NR_ulimit is 58 on Linux 2.6.22/i386
 558 and
 559 .BR vserver (2)      \" __NR_vserver is 273 on Linux 2.6.22/i386
 560 (see also
 561 .BR unimplemented (2)).
 562 However,
 563 .BR ftime (3),
 564 .BR profil (3)
 565 and
 566 .BR ulimit (3)
 567 exist as library routines.
 568 The slot for
 569 .BR phys (2)
 570 is in use since kernel 2.1.116 for
 571 .BR umount (2);
 572 .BR phys (2)
 573 will never be implemented.
 574 .IP *
 575 The
 576 .BR getpmsg (2)
 577 and
 578 .BR putpmsg (2)
 579 calls are for kernels patched to support STREAMS,
 580 and may never be in the standard kernel.
 581 .\" The security call is for future use.
 582 .PP
 583 Roughly speaking, the code belonging to the system call
 584 with number __NR_xxx defined in
 585 .I /usr/include/asm/unistd.h
 586 can be found in the kernel source in the routine
 587 .IR sys_xxx ().
 588 (The dispatch table for i386 can be found in
 589 .IR /usr/src/linux/arch/i386/kernel/entry.S .)
 590 There are many exceptions, however, mostly because
 591 older system calls were superseded by newer ones,
 592 and this has been treated somewhat unsystematically.
 593 On platforms with
 594 proprietary OS emulation, such as parisc, sparc, sparc64 and alpha,
 595 there are many additional system calls; mips64 also contains a full
 596 set of 32-bit system calls.
 597
 598 Over time, changes to the interfaces of some system calls have been
 599 necessary.
 600 One reason for such changes was the need to increase the size of
 601 structures or scalar values passed to the system call.
 602 Because of these changes, there are now various groups
 603 of related system calls
 604 (e.g.,
 605 .BR truncate (2)
 606 and
 607 .BR ftruncate64 (2))
 608 which perform similar tasks, but which vary in
 609 details such as the size of their arguments.
 610 (As noted earlier, applications are generally unaware of this:
 611 the glibc wrapper functions do some work to ensure that the right
 612 system call is invoked, and that ABI compatibility is
 613 preserved for old binaries.)
 614 Examples of systems calls that exist in multiple versions are
 615 the following:
 616 .IP * 3
 617 By now there are three different versions of
 618 .BR stat (2):
 619 .IR sys_stat ()
 620 (slot
 621 .IR __NR_oldstat ),
 622 .IR sys_newstat ()
 623 (slot
 624 .IR __NR_stat ),
 625 and
 626 .IR sys_stat64()
 627 (slot
 628 .IR __NR_stat64 ),
 629 with the last being the most current.
 630 .\" e.g., on 2.6.22/i386: __NR_oldstat 18, __NR_stat 106, __NR_stat64 195
 631 .\" The stat system calls deal with three different data structures,
 632 .\" defined in include/asm-i386/stat.h: __old_kernel_stat, stat, stat64
 633 A similar story applies for
 634 .BR lstat (2)
 635 and
 636 .BR fstat (2).
 637 .IP *
 638 Similarly, the defines
 639 .IR __NR_oldolduname ,
 640 .IR __NR_olduname ,
 641 and
 642 .IR __NR_uname
 643 refer to the routines
 644 .IR sys_olduname (),
 645 .IR sys_uname ()
 646 and
 647 .IR sys_newuname ().
 648 .IP *
 649 In Linux 2.0, a new version of
 650 .BR vm86 (2)
 651 appeared, with the old and the new kernel routines being named
 652 .IR sys_vm86old ()
 653 and
 654 .IR sys_vm86 ().
 655 .IP *
 656 In Linux 2.4, a new version of
 657 .BR getrlimit (2)
 658 appeared, with the old and the new kernel routines being named
 659 .IR sys_old_getrlimit ()
 660 (slot
 661 .IR __NR_getrlimit )
 662 and
 663 .IR sys_getrlimit ()
 664 (slot
 665 .IR __NR_ugetrlimit ).
 666 .IP *
 667 Linux 2.4 increased the size of user and group IDs from 16 to 32 bits.
 668 .\" 64 bit off_t changes: ftruncate64, *stat64,
 669 .\" fcntl64 (because of the flock structure), getdents64, *statfs64
 670 To support this change, a range of system calls were added
 671 (e.g.,
 672 .BR chown32 (2),
 673 .BR getuid32 (2),
 674 .BR getgroups32 (2),
 675 .BR setresuid32 (2)),
 676 superseding earlier calls of the same name without the
 677 "32" suffix.
 678 .IP *
 679 Linux 2.4 added support for applications on 32-bit architectures
 680 to access large files (i.e., files for which the sizes and
 681 file offsets can't be represented in 32 bits.)
 682 To support this change, replacements were required for system calls
 683 that deal with file offsets and sizes.
 684 Thus the following system calls were added:
 685 .BR fcntl64 (2),
 686 .BR ftruncate64 (2),
 687 .BR getdents64 (2),
 688 .BR stat64 (2),
 689 .BR statfs64 (2),
 690 and their analogs that work with file descriptors or
 691 symbolic links.
 692 These system calls supersede the older system calls
 693 which, except in the case of the "stat" calls,
 694 have the same name without the "64" suffix.
 695 .sp
 696 On newer platforms that only have 64-bit file access and 32-bit uids
 697 (e.g., alpha, ia64, s390x) there are no *64 or *32 calls.
 698 Where the *64 and *32 calls exist, the other versions are obsolete.
 699 .IP *
 700 The
 701 .I rt_sig*
 702 calls were added in kernel 2.2 to support the addition
 703 of real-time signals (see
 704 .BR signal (7)).
 705 These system calls supersede the older system calls of the same
 706 name without the "rt_" prefix.
 707 .IP *
 708 The
 709 .BR select (2)
 710 and
 711 .BR mmap (2)
 712 system calls use five or more parameters,
 713 which caused problems the way
 714 parameter passing on the i386 used to be set up.
 715 Thus, while other architectures have
 716 .IR sys_select ()
 717 and
 718 .IR sys_mmap ()
 719 corresponding to
 720 .IR __NR_select
 721 and
 722 .IR __NR_mmap ,
 723 on i386 one finds
 724 .IR old_select ()
 725 and
 726 .IR old_mmap ()
 727 (routines that use a pointer to a
 728 parameter block) instead.
 729 These days passing five parameters
 730 is not a problem any more, and there is a
 731 .IR __NR__newselect
 732 .\" (used by libc 6)
 733 that corresponds directly to
 734 .IR sys_select ()
 735 and similarly
 736 .IR __NR_mmap2 .
 737 .\" .PP
 738 .\" Two system call numbers,
 739 .\" .IR __NR__llseek
 740 .\" and
 741 .\" .IR __NR__sysctl
 742 .\" have an additional underscore absent in
 743 .\" .IR sys_llseek ()
 744 .\" and
 745 .\" .IR sys_sysctl ().
 746 .\"
 747 .\" In kernel 2.1.81,
 748 .\" .BR lchown (2)
 749 .\" and
 750 .\" .BR chown (2)
 751 .\" were swapped; that is,
 752 .\" .BR lchown (2)
 753 .\" was added with the semantics that were then current for
 754 .\" .BR chown (2),
 755 .\" and the semantics of the latter call were changed to what
 756 .\" they are today.
 757 .SH SEE ALSO
 758 .BR syscall (2),
 759 .BR unimplemented (2)