1SYSCALLS(2) Linux Programmer's Manual SYSCALLS(2)
2
6 syscalls - Linux system calls
7
9 Linux system calls.
10
12 The system call is the fundamental interface between an application and
13 the Linux kernel.
14 System calls and library wrapper functions
16 System calls are generally not invoked directly, but rather via wrapper
17 functions in glibc (or perhaps some other library). For details of
18 direct invocation of a system call, see intro(2). Often, but not
19 always, the name of the wrapper function is the same as the name of the
20 system call that it invokes. For example, glibc contains a function
21 truncate() which invokes the underlying "truncate" system call.
22 Often the glibc wrapper function is quite thin, doing little work other
24 than copying arguments to the right registers before invoking the sys‐
25 tem call, and then setting errno appropriately after the system call
26 has returned. (These are the same steps that are performed by
27 syscall(2), which can be used to invoke system calls for which no wrap‐
28 per function is provided.) Note: system calls indicate a failure by
29 returning a negative error number to the caller; when this happens, the
30 wrapper function negates the returned error number (to make it posi‐
31 tive), copies it to errno, and returns -1 to the caller of the wrapper.
32 Sometimes, however, the wrapper function does some extra work before
34 invoking the system call. For example, nowadays there are (for reasons
35 described below) two related system calls, truncate(2) and trun‐
36 cate64(2), and the glibc truncate() wrapper function checks which of
37 those system calls are provided by the kernel and determines which
38 should be employed.
39 System call list
41 Below is a list of the Linux system calls. In the list, the Kernel
42 column indicates the kernel version for those system calls that were
43 new in Linux 2.2, or have appeared since that kernel version. Note the
44 following points:
45 * Where no kernel version is indicated, the system call appeared in
47 kernel 1.0 or earlier.
48 * Where a system call is marked "1.2" this means the system call prob‐
50 ably appeared in a 1.1.x kernel version, and first appeared in a
51 stable kernel with 1.2. (Development of the 1.2 kernel was initi‐
52 ated from a branch of kernel 1.0.6 via the 1.1.x unstable kernel
53 series.)
54 * Where a system call is marked "2.0" this means the system call prob‐
56 ably appeared in a 1.3.x kernel version, and first appeared in a
57 stable kernel with 2.0. (Development of the 2.0 kernel was initi‐
58 ated from a branch of kernel 1.2.x, somewhere around 1.2.10, via the
59 1.3.x unstable kernel series.)
60 * Where a system call is marked "2.2" this means the system call prob‐
62 ably appeared in a 2.1.x kernel version, and first appeared in a
63 stable kernel with 2.2.0. (Development of the 2.2 kernel was initi‐
64 ated from a branch of kernel 2.0.21 via the 2.1.x unstable kernel
65 series.)
66 * Where a system call is marked "2.4" this means the system call prob‐
68 ably appeared in a 2.3.x kernel version, and first appeared in a
69 stable kernel with 2.4.0. (Development of the 2.4 kernel was initi‐
70 ated from a branch of kernel 2.2.8 via the 2.3.x unstable kernel
71 series.)
72 * Where a system call is marked "2.6" this means the system call prob‐
74 ably appeared in a 2.5.x kernel version, and first appeared in a
75 stable kernel with 2.6.0. (Development of kernel 2.6 was initiated
76 from a branch of kernel 2.4.15 via the 2.5.x unstable kernel
77 series.)
78 * Starting with kernel 2.6.0, the development model changed, and new
80 system calls may appear in each 2.6.x release. In this case, the
81 exact version number where the system call appeared is shown. This
82 convention continues with the 3.x kernel series, which followed on
83 from kernel 2.6.39, and the 4.x kernel series, which followed on
84 from kernel 3.19.
85 * In some cases, a system call was added to a stable kernel series
87 after it branched from the previous stable kernel series, and then
88 backported into the earlier stable kernel series. For example some
89 system calls that appeared in 2.6.x were also backported into a
90 2.4.x release after 2.4.15. When this is so, the version where the
91 system call appeared in both of the major kernel series is listed.
92 The list of system calls that are available as at kernel 4.11 (or in a
94 few cases only on older kernels) is as follows:
95 System call Kernel Notes
97 ────────────────────────────────────────────────────────────────────
98 _llseek(2) 1.2
100 _newselect(2) 2.0
101 _sysctl(2) 2.0
102 accept(2) 2.0 See notes on socketcall(2)
103 accept4(2) 2.6.28
104 access(2) 1.0
105 acct(2) 1.0
106 add_key(2) 2.6.10
107 adjtimex(2) 1.0
108 alarm(2) 1.0
109 alloc_hugepages(2) 2.5.36 Removed in 2.5.44
110 bdflush(2) 1.2 Deprecated (does nothing)
111 since 2.6
112 bind(2) 2.0 See notes on socketcall(2)
113 bpf(2) 3.18
114 brk(2) 1.0
115 cacheflush(2) 1.2 Not on x86
116 capget(2) 2.2
117 capset(2) 2.2
118 chdir(2) 1.0
119 chmod(2) 1.0
120 chown(2) 2.2 See chown(2) for
121 version details
122 chown32(2) 2.4
123 chroot(2) 1.0
124 clock_adjtime(2) 2.6.39
125 clock_getres(2) 2.6
126 clock_gettime(2) 2.6
127 clock_nanosleep(2) 2.6
128 clock_settime(2) 2.6
129 clone(2) 1.0
130 close(2) 1.0
131 connect(2) 2.0 See notes on socketcall(2)
132 copy_file_range(2) 4.5
134 creat(2) 1.0
135 create_module(2) 1.0 Removed in 2.6
136 delete_module(2) 1.0
137 dup(2) 1.0
138 dup2(2) 1.0
139 dup3(2) 2.6.27
140 epoll_create(2) 2.6
141 epoll_create1(2) 2.6.27
142 epoll_ctl(2) 2.6
143 epoll_pwait(2) 2.6.19
144 epoll_wait(2) 2.6
145 eventfd(2) 2.6.22
146 eventfd2(2) 2.6.27
147 execve(2) 1.0
148 execveat(2) 3.19
149 exit(2) 1.0
150 exit_group(2) 2.6
151 faccessat(2) 2.6.16
152 fadvise64(2) 2.6
153 fadvise64_64(2) 2.6
154 fallocate(2) 2.6.23
155 fanotify_init(2) 2.6.37
156 fanotify_mark(2) 2.6.37
157 fchdir(2) 1.0
158 fchmod(2) 1.0
159 fchmodat(2) 2.6.16
160 fchown(2) 1.0
161 fchown32(2) 2.4
162 fchownat(2) 2.6.16
163 fcntl(2) 1.0
164 fcntl64(2) 2.4
165 fdatasync(2) 2.0
166 fgetxattr(2) 2.6; 2.4.18
167 finit_module(2) 3.8
168 flistxattr(2) 2.6; 2.4.18
169 flock(2) 2.0
170 fork(2) 1.0
171 free_hugepages(2) 2.5.36 Removed in 2.5.44
172 fremovexattr(2) 2.6; 2.4.18
173 fsetxattr(2) 2.6; 2.4.18
174 fstat(2) 1.0
175 fstat64(2) 2.4
176 fstatat64(2) 2.6.16
177 fstatfs(2) 1.0
178 fstatfs64(2) 2.6
179 fsync(2) 1.0
180 ftruncate(2) 1.0
181 ftruncate64(2) 2.4
182 futex(2) 2.6
183 futimesat(2) 2.6.16
184 get_kernel_syms(2) 1.0 Removed in 2.6
185 get_mempolicy(2) 2.6.6
186 get_robust_list(2) 2.6.17
187 get_thread_area(2) 2.6
188 getcpu(2) 2.6.19
189 getcwd(2) 2.2
190 getdents(2) 2.0
191 getdents64(2) 2.4
192 getegid(2) 1.0
193 getegid32(2) 2.4
194 geteuid(2) 1.0
195 geteuid32(2) 2.4
196 getgid(2) 1.0
197 getgid32(2) 2.4
198 getgroups(2) 1.0
200 getgroups32(2) 2.4
201 getitimer(2) 1.0
202 getpeername(2) 2.0 See notes on socketcall(2)
203 getpagesize(2) 2.0 Not on x86
204 getpgid(2) 1.0
205 getpgrp(2) 1.0
206 getpid(2) 1.0
207 getppid(2) 1.0
208 getpriority(2) 1.0
209 getrandom(2) 3.17
210 getresgid(2) 2.2
211 getresgid32(2) 2.4
212 getresuid(2) 2.2
213 getresuid32(2) 2.4
214 getrlimit(2) 1.0
215 getrusage(2) 1.0
216 getsid(2) 2.0
217 getsockname(2) 2.0 See notes on socketcall(2)
218 getsockopt(2) 2.0 See notes on socketcall(2)
219 gettid(2) 2.4.11
220 gettimeofday(2) 1.0
221 getuid(2) 1.0
222 getuid32(2) 2.4
223 getunwind(2) 2.4.8 ia64; deprecated
224 getxattr(2) 2.6; 2.4.18
225 init_module(2) 1.0
226 inotify_add_watch(2) 2.6.13
227 inotify_init(2) 2.6.13
228 inotify_init1(2) 2.6.27
229 inotify_rm_watch(2) 2.6.13
230 io_cancel(2) 2.6
231 io_destroy(2) 2.6
232 io_getevents(2) 2.6
233 io_setup(2) 2.6
234 io_submit(2) 2.6
235 ioctl(2) 1.0
236 ioperm(2) 1.0
237 iopl(2) 1.0
238 ioprio_get(2) 2.6.13
239 ioprio_set(2) 2.6.13
240 ipc(2) 1.0
241 kcmp(2) 3.5
242 kern_features(2) 3.7 Sparc64
243 kexec_file_load(2) 3.17
244 kexec_load(2) 2.6.13
245 keyctl(2) 2.6.10
246 kill(2) 1.0
247 lchown(2) 1.0 See chown(2) for
248 version details
249 lchown32(2) 2.4
250 lgetxattr(2) 2.6; 2.4.18
251 link(2) 1.0
252 linkat(2) 2.6.16
253 listen(2) 2.0 See notes on socketcall(2)
254 listxattr(2) 2.6; 2.4.18
255 llistxattr(2) 2.6; 2.4.18
256 lookup_dcookie(2) 2.6
257 lremovexattr(2) 2.6; 2.4.18
258 lseek(2) 1.0
259 lsetxattr(2) 2.6; 2.4.18
260 lstat(2) 1.0
261 lstat64(2) 2.4
262 madvise(2) 2.4
263 mbind(2) 2.6.6
264 membarrier(2) 3.17
266 memfd_create(2) 3.17
267 migrate_pages(2) 2.6.16
268 mincore(2) 2.4
269 mkdir(2) 1.0
270 mkdirat(2) 2.6.16
271 mknod(2) 1.0
272 mknodat(2) 2.6.16
273 mlock(2) 2.0
274 mlock2(2) 4.4
275 mlockall(2) 2.0
276 mmap(2) 1.0
277 mmap2(2) 2.4
278 modify_ldt(2) 1.0
279 mount(2) 1.0
280 move_pages(2) 2.6.18
281 mprotect(2) 1.0
282 mq_getsetattr(2) 2.6.6
283 mq_notify(2) 2.6.6
284 mq_open(2) 2.6.6
285 mq_timedreceive(2) 2.6.6
286 mq_timedsend(2) 2.6.6
287 mq_unlink(2) 2.6.6
288 mremap(2) 2.0
289 msgctl(2) 2.0 See notes on ipc(2)
290 msgget(2) 2.0 See notes on ipc(2)
291 msgrcv(2) 2.0 See notes on ipc(2)
292 msgsnd(2) 2.0 See notes on ipc(2)
293 msync(2) 2.0
294 munlock(2) 2.0
295 munlockall(2) 2.0
296 munmap(2) 1.0
297 name_to_handle_at(2) 2.6.39
298 nanosleep(2) 2.0
299 nfsservctl(2) 2.2 Removed in 3.1
300 nice(2) 1.0
301 oldfstat(2) 1.0
302 oldlstat(2) 1.0
303 oldolduname(2) 1.0
304 oldstat(2) 1.0
305 olduname(2) 1.0
306 open(2) 1.0
307 open_by_handle_at(2) 2.6.39
308 openat(2) 2.6.16
309 pause(2) 1.0
310 pciconfig_iobase(2) 2.2.15; 2.4 Not on x86
311 pciconfig_read(2) 2.0.26; 2.2 Not on x86
312 pciconfig_write(2) 2.0.26; 2.2 Not on x86
313 perf_event_open(2) 2.6.31 Was perf_counter_open() in
314 2.6.31; renamed in 2.6.32
315 personality(2) 1.2
316 perfctr(2) 2.2 Sparc; removed in 2.6.34
317 perfmonctl(2) 2.4 ia64
318 pipe(2) 1.0
319 pipe2(2) 2.6.27
320 pivot_root(2) 2.4
321 pkey_alloc(2) 4.8
322 pkey_free(2) 4.8
323 pkey_mprotect(2) 4.8
324 poll(2) 2.0.36; 2.2
325 ppc_rtas(2) 2.6.2 PowerPC only
326 ppc_swapcontext(2) 2.6.3 PowerPC only
327 ppoll(2) 2.6.16
328 prctl(2) 2.2
329 pread64(2) Added as "pread" in 2.2;
332 renamed "pread64" in 2.6
333 preadv(2) 2.6.30
334 preadv2(2) 4.6
335 prlimit64(2) 2.6.36
336 process_vm_readv(2) 3.2
337 process_vm_writev(2) 3.2
338 pselect6(2) 2.6.16
339 ptrace(2) 1.0
340 pwrite64(2) Added as "pwrite" in 2.2;
341 renamed "pwrite64" in 2.6
342 pwritev(2) 2.6.30
343 pwritev2(2) 4.6
344 query_module(2) 2.2 Removed in 2.6
345 quotactl(2) 1.0
346 read(2) 1.0
347 readahead(2) 2.4.13
348 readdir(2) 1.0
349 readlink(2) 1.0
350 readlinkat(2) 2.6.16
351 readv(2) 2.0
352 reboot(2) 1.0
353 recv(2) 2.0 See notes on socketcall(2)
354 recvfrom(2) 2.0 See notes on socketcall(2)
355 recvmsg(2) 2.0 See notes on socketcall(2)
356 recvmmsg(2) 2.6.33
357 remap_file_pages(2) 2.6 Deprecated since 3.16
358 removexattr(2) 2.6; 2.4.18
359 rename(2) 1.0
360 renameat(2) 2.6.16
361 renameat2(2) 3.15
362 request_key(2) 2.6.10
363 restart_syscall(2) 2.6
364 rmdir(2) 1.0
365 rt_sigaction(2) 2.2
366 rt_sigpending(2) 2.2
367 rt_sigprocmask(2) 2.2
368 rt_sigqueueinfo(2) 2.2
369 rt_sigreturn(2) 2.2
370 rt_sigsuspend(2) 2.2
371 rt_sigtimedwait(2) 2.2
372 rt_tgsigqueueinfo(2) 2.6.31
373 s390_runtime_instr(2) 3.7 s390 only
374 s390_pci_mmio_read(2) 3.19 s390 only
375 s390_pci_mmio_write(2) 3.19 s390 only
376 s390_sthyi(2) 4.15 s390 only
377 sched_get_priority_max(2) 2.0
378 sched_get_priority_min(2) 2.0
379 sched_getaffinity(2) 2.6
380 sched_getattr(2) 3.14
381 sched_getparam(2) 2.0
382 sched_getscheduler(2) 2.0
383 sched_rr_get_interval(2) 2.0
384 sched_setaffinity(2) 2.6
385 sched_setattr(2) 3.14
386 sched_setparam(2) 2.0
387 sched_setscheduler(2) 2.0
388 sched_yield(2) 2.0
389 seccomp(2) 3.17
390 select(2) 1.0
391 semctl(2) 2.0 See notes on ipc(2)
392 semget(2) 2.0 See notes on ipc(2)
393 semop(2) 2.0 See notes on ipc(2)
394 semtimedop(2) 2.6; 2.4.22
395 send(2) 2.0 See notes on socketcall(2)
396 sendfile(2) 2.2
398 sendfile64(2) 2.6; 2.4.19
399 sendmmsg(2) 3.0
400 sendmsg(2) 2.0 See notes on socketcall(2)
401 sendto(2) 2.0 See notes on socketcall(2)
402 set_mempolicy(2) 2.6.6
403 set_robust_list(2) 2.6.17
404 set_thread_area(2) 2.6
405 set_tid_address(2) 2.6
406 setdomainname(2) 1.0
407 setfsgid(2) 1.2
408 setfsgid32(2) 2.4
409 setfsuid(2) 1.2
410 setfsuid32(2) 2.4
411 setgid(2) 1.0
412 setgid32(2) 2.4
413 setgroups(2) 1.0
414 setgroups32(2) 2.4
415 sethostname(2) 1.0
416 setitimer(2) 1.0
417 setns(2) 3.0
418 setpgid(2) 1.0
419 setpriority(2) 1.0
420 setregid(2) 1.0
421 setregid32(2) 2.4
422 setresgid(2) 2.2
423 setresgid32(2) 2.4
424 setresuid(2) 2.2
425 setresuid32(2) 2.4
426 setreuid(2) 1.0
427 setreuid32(2) 2.4
428 setrlimit(2) 1.0
429 setsid(2) 1.0
430 setsockopt(2) 2.0 See notes on socketcall(2)
431 settimeofday(2) 1.0
432 setuid(2) 1.0
433 setuid32(2) 2.4
434 setup(2) 1.0 Removed in 2.2
435 setxattr(2) 2.6; 2.4.18
436 sgetmask(2) 1.0
437 shmat(2) 2.0 See notes on ipc(2)
438 shmctl(2) 2.0 See notes on ipc(2)
439 shmdt(2) 2.0 See notes on ipc(2)
440 shmget(2) 2.0 See notes on ipc(2)
441 shutdown(2) 2.0 See notes on socketcall(2)
442 sigaction(2) 1.0
443 sigaltstack(2) 2.2
444 signal(2) 1.0
445 signalfd(2) 2.6.22
446 signalfd4(2) 2.6.27
447 sigpending(2) 1.0
448 sigprocmask(2) 1.0
449 sigreturn(2) 1.0
450 sigsuspend(2) 1.0
451 socket(2) 2.0 See notes on socketcall(2)
452 socketcall(2) 1.0
453 socketpair(2) 2.0 See notes on socketcall(2)
454 splice(2) 2.6.17
455 spu_create(2) 2.6.16 PowerPC only
456 spu_run(2) 2.6.16 PowerPC only
457 ssetmask(2) 1.0
458 stat(2) 1.0
459 stat64(2) 2.4
460 statfs(2) 1.0
461 statfs64(2) 2.6
462 statx(2) 4.11
464 stime(2) 1.0
465 subpage_prot(2) 2.6.25 PowerPC only
466 swapoff(2) 1.0
467 swapon(2) 1.0
468 symlink(2) 1.0
469 symlinkat(2) 2.6.16
470 sync(2) 1.0
471 sync_file_range(2) 2.6.17
472 sync_file_range2(2) 2.6.22
473 syncfs(2) 2.6.39
474 sysfs(2) 1.2
475 sysinfo(2) 1.0
476 syslog(2) 1.0
477 tee(2) 2.6.17
478 tgkill(2) 2.6
479 time(2) 1.0
480 timer_create(2) 2.6
481 timer_delete(2) 2.6
482 timer_getoverrun(2) 2.6
483 timer_gettime(2) 2.6
484 timer_settime(2) 2.6
485 timerfd_create(2) 2.6.25
486 timerfd_gettime(2) 2.6.25
487 timerfd_settime(2) 2.6.25
488 times(2) 1.0
489 tkill(2) 2.6; 2.4.22
490 truncate(2) 1.0
491 truncate64(2) 2.4
492 ugetrlimit(2) 2.4
493 umask(2) 1.0
494 umount(2) 1.0
495 umount2(2) 2.2
496 uname(2) 1.0
497 unlink(2) 1.0
498 unlinkat(2) 2.6.16
499 unshare(2) 2.6.16
500 uselib(2) 1.0
501 ustat(2) 1.0
502 userfaultfd(2) 4.3
503 utime(2) 1.0
504 utimensat(2) 2.6.22
505 utimes(2) 2.2
506 utrap_install(2) 2.2 Sparc only
507 vfork(2) 2.2
508 vhangup(2) 1.0
509 vm86old(2) 1.0 Was "vm86"; renamed in
510 2.0.28/2.2
511 vm86(2) 2.0.28; 2.2
512 vmsplice(2) 2.6.17
513 wait4(2) 1.0
514 waitid(2) 2.6.10
515 waitpid(2) 1.0
516 write(2) 1.0
517 writev(2) 2.0
518 On many platforms, including x86-32, socket calls are all multiplexed
520 (via glibc wrapper functions) through socketcall(2) and similarly Sys‐
521 tem V IPC calls are multiplexed through ipc(2).
522 Although slots are reserved for them in the system call table, the fol‐
524 lowing system calls are not implemented in the standard kernel:
525 afs_syscall(2), break(2), ftime(2), getpmsg(2), gtty(2), idle(2),
526 lock(2), madvise1(2), mpx(2), phys(2), prof(2), profil(2), putpmsg(2),
527 security(2), stty(2), tuxcall(2), ulimit(2), and vserver(2) (see also
528 unimplemented(2)). However, ftime(3), profil(3), and ulimit(3) exist
529 as library routines. The slot for phys(2) is in use since kernel
530 2.1.116 for umount(2); phys(2) will never be implemented. The
531 getpmsg(2) and putpmsg(2) calls are for kernels patched to support
532 STREAMS, and may never be in the standard kernel.
533 There was briefly set_zone_reclaim(2), added in Linux 2.6.13, and
535 removed in 2.6.16; this system call was never available to user space.
536
538 Roughly speaking, the code belonging to the system call with number
539 __NR_xxx defined in /usr/include/asm/unistd.h can be found in the Linux
540 kernel source in the routine sys_xxx(). (The dispatch table for i386
541 can be found in /usr/src/linux/arch/i386/kernel/entry.S.) There are
542 many exceptions, however, mostly because older system calls were super‐
543 seded by newer ones, and this has been treated somewhat unsystemati‐
544 cally. On platforms with proprietary operating-system emulation, such
545 as parisc, sparc, sparc64, and alpha, there are many additional system
546 calls; mips64 also contains a full set of 32-bit system calls.
547 Over time, changes to the interfaces of some system calls have been
549 necessary. One reason for such changes was the need to increase the
550 size of structures or scalar values passed to the system call. Because
551 of these changes, certain architectures (notably, longstanding 32-bit
552 architectures such as i386) now have various groups of related system
553 calls (e.g., truncate(2) and truncate64(2)) which perform similar
554 tasks, but which vary in details such as the size of their arguments.
555 (As noted earlier, applications are generally unaware of this: the
556 glibc wrapper functions do some work to ensure that the right system
557 call is invoked, and that ABI compatibility is preserved for old bina‐
558 ries.) Examples of systems calls that exist in multiple versions are
559 the following:
560 * By now there are three different versions of stat(2): sys_stat()
562 (slot __NR_oldstat), sys_newstat() (slot __NR_stat), and
563 sys_stat64() (slot __NR_stat64), with the last being the most cur‐
564 rent. A similar story applies for lstat(2) and fstat(2).
565 * Similarly, the defines __NR_oldolduname, __NR_olduname, and
567 __NR_uname refer to the routines sys_olduname(), sys_uname() and
568 sys_newuname().
569 * In Linux 2.0, a new version of vm86(2) appeared, with the old and
571 the new kernel routines being named sys_vm86old() and sys_vm86().
572 * In Linux 2.4, a new version of getrlimit(2) appeared, with the old
574 and the new kernel routines being named sys_old_getrlimit() (slot
575 __NR_getrlimit) and sys_getrlimit() (slot __NR_ugetrlimit).
576 * Linux 2.4 increased the size of user and group IDs from 16 to 32
578 bits. To support this change, a range of system calls were added
579 (e.g., chown32(2), getuid32(2), getgroups32(2), setresuid32(2)),
580 superseding earlier calls of the same name without the "32" suffix.
581 * Linux 2.4 added support for applications on 32-bit architectures to
583 access large files (i.e., files for which the sizes and file offsets
584 can't be represented in 32 bits.) To support this change, replace‐
585 ments were required for system calls that deal with file offsets and
586 sizes. Thus the following system calls were added: fcntl64(2), get‐
587 dents64(2), stat64(2), statfs64(2), truncate64(2), and their analogs
588 that work with file descriptors or symbolic links. These system
589 calls supersede the older system calls which, except in the case of
590 the "stat" calls, have the same name without the "64" suffix.
591 On newer platforms that only have 64-bit file access and 32-bit
593 UIDs/GIDs (e.g., alpha, ia64, s390x, x86-64), there is just a single
594 version of the UID/GID and file access system calls. On platforms
595 (typically, 32-bit platforms) where the *64 and *32 calls exist, the
596 other versions are obsolete.
597 * The rt_sig* calls were added in kernel 2.2 to support the addition
599 of real-time signals (see signal(7)). These system calls supersede
600 the older system calls of the same name without the "rt_" prefix.
601 * The select(2) and mmap(2) system calls use five or more arguments,
603 which caused problems in the way argument passing on the i386 used
604 to be set up. Thus, while other architectures have sys_select() and
605 sys_mmap() corresponding to __NR_select and __NR_mmap, on i386 one
606 finds old_select() and old_mmap() (routines that use a pointer to an
607 argument block) instead. These days passing five arguments is not a
608 problem any more, and there is a __NR__newselect that corresponds
609 directly to sys_select() and similarly __NR_mmap2.
610
612 intro(2), syscall(2), unimplemented(2), errno(3), libc(7), vdso(7)
613
615 This page is part of release 4.15 of the Linux man-pages project. A
616 description of the project, information about reporting bugs, and the
617 latest version of this page, can be found at
618 https://www.kernel.org/doc/man-pages/.
619Linux 2018-02-02 SYSCALLS(2)