syscalls - Linux system calls
Linux system calls.
The system call is the fundamental interface between an application and the
Linux kernel.
System calls are generally not invoked directly, but rather via wrapper
functions in glibc (or perhaps some other library). For details of direct
invocation of a system call, see
intro(2). Often, but not always, the
name of the wrapper function is the same as the name of the system call that
it invokes. For example, glibc contains a function
chdir() which
invokes the underlying "chdir" system call.
Often the glibc wrapper function is quite thin, doing little work other than
copying arguments to the right registers before invoking the system call, and
then setting
errno appropriately after the system call has returned.
(These are the same steps that are performed by
syscall(2), which can
be used to invoke system calls for which no wrapper function is provided.)
Note: system calls indicate a failure by returning a negative error number to
the caller on architectures without a separate error register/flag, as noted
in
syscall(2); when this happens, the wrapper function negates the
returned error number (to make it positive), copies it to
errno, and
returns -1 to the caller of the wrapper.
Sometimes, however, the wrapper function does some extra work before invoking
the system call. For example, nowadays there are (for reasons described below)
two related system calls,
truncate(2) and
truncate64(2), and the
glibc
truncate() wrapper function checks which of those system calls
are provided by the kernel and determines which should be employed.
Below is a list of the Linux system calls. In the list, the
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:
- *
- Where no kernel version is indicated, the system call appeared in kernel
1.0 or earlier.
- *
- Where a system call is marked "1.2" this means the system call
probably appeared in a 1.1.x kernel version, and first appeared in a
stable kernel with 1.2. (Development of the 1.2 kernel was initiated from
a branch of kernel 1.0.6 via the 1.1.x unstable kernel series.)
- *
- Where a system call is marked "2.0" this means the system call
probably appeared in a 1.3.x kernel version, and first appeared in a
stable kernel with 2.0. (Development of the 2.0 kernel was initiated from
a branch of kernel 1.2.x, somewhere around 1.2.10, via the 1.3.x unstable
kernel series.)
- *
- 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. (Development of the 2.2 kernel was initiated
from a branch of kernel 2.0.21 via the 2.1.x unstable kernel series.)
- *
- 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. (Development of the 2.4 kernel was initiated
from a branch of kernel 2.2.8 via the 2.3.x unstable kernel series.)
- *
- 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. (Development of kernel 2.6 was initiated from a
branch of kernel 2.4.15 via the 2.5.x unstable kernel series.)
- *
- Starting with kernel 2.6.0, the development model changed, and new system
calls may appear in each 2.6.x release. In this case, the exact version
number where the system call appeared is shown. This convention continues
with the 3.x kernel series, which followed on from kernel 2.6.39; and the
4.x kernel series, which followed on from kernel 3.19; and the 5.x kernel
series, which followed on from kernel 4.20.
- *
- In some cases, a system call was added to a stable kernel series after it
branched from the previous stable kernel series, and then backported into
the earlier stable kernel series. For example some system calls that
appeared in 2.6.x were also backported into a 2.4.x release after 2.4.15.
When this is so, the version where the system call appeared in both of the
major kernel series is listed.
The list of system calls that are available as at kernel 4.19 (or in a few cases
only on older kernels) is as follows:
| System call |
Kernel |
Notes |
|
|
|
|
|
|
| _llseek(2) |
1.2 |
|
| _newselect(2) |
2.0 |
|
| _sysctl(2) |
2.0 |
|
| accept(2) |
2.0 |
See notes on socketcall(2) |
| accept4(2) |
2.6.28 |
|
| access(2) |
1.0 |
|
| acct(2) |
1.0 |
|
| add_key(2) |
2.6.10 |
|
| adjtimex(2) |
1.0 |
|
| alarm(2) |
1.0 |
|
| alloc_hugepages(2) |
2.5.36 |
Removed in 2.5.44 |
| . |
|
|
| arc_gettls(2) |
3.9 |
ARC only |
| arc_settls(2) |
3.9 |
ARC only |
| . |
|
|
| arc_usr_cmpxchg(2) |
4.9 |
ARC only |
| . |
|
|
| arch_prctl(2) |
2.6 |
x86_64, x86 since 4.12 |
| . |
|
|
| atomic_barrier(2) |
2.6.34 |
m68k only |
| atomic_cmpxchg_32(2) |
2.6.34 |
m68k only |
| bdflush(2) |
1.2 |
Deprecated (does nothing) since 2.6 |
| bfin_spinlock(2) |
2.6.22 |
Blackfin only (port removed in Linux 4.17) |
| bind(2) |
2.0 |
See notes on socketcall(2) |
| bpf(2) |
3.18 |
|
| brk(2) |
1.0 |
|
| breakpoint(2) |
2.2 |
ARM OABI only, defined with __ARM_NR prefix |
| cacheflush(2) |
1.2 |
Not on x86 |
| capget(2) |
2.2 |
|
| capset(2) |
2.2 |
|
| chdir(2) |
1.0 |
|
| chmod(2) |
1.0 |
|
| chown(2) |
2.2 |
See chown(2) for version details |
| chown32(2) |
2.4 |
|
| chroot(2) |
1.0 |
|
| clock_adjtime(2) |
2.6.39 |
|
| clock_getres(2) |
2.6 |
|
| clock_gettime(2) |
2.6 |
|
| clock_nanosleep(2) |
2.6 |
|
| clock_settime(2) |
2.6 |
|
| clone2(2) |
2.4 |
IA-64 only |
| clone(2) |
1.0 |
|
| clone3(2) |
5.3 |
|
| close(2) |
1.0 |
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| cmpxchg_badaddr(2) |
2.6.36 |
Tile only (port removed in Linux 4.17) |
| connect(2) |
2.0 |
See notes on socketcall(2) |
| copy_file_range(2) |
4.5 |
|
| creat(2) |
1.0 |
|
| create_module(2) |
1.0 |
Removed in 2.6 |
| delete_module(2) |
1.0 |
|
| . |
|
|
| . |
|
|
| dma_memcpy(2) |
2.6.22 |
Blackfin only (port removed in Linux 4.17) |
| dup(2) |
1.0 |
|
| dup2(2) |
1.0 |
|
| dup3(2) |
2.6.27 |
|
| epoll_create(2) |
2.6 |
|
| epoll_create1(2) |
2.6.27 |
|
| epoll_ctl(2) |
2.6 |
|
| epoll_pwait(2) |
2.6.19 |
|
| epoll_wait(2) |
2.6 |
|
| eventfd(2) |
2.6.22 |
|
| eventfd2(2) |
2.6.27 |
|
| execv(2) |
2.0 |
SPARC/SPARC64 only, for compatibility with SunOS |
| execve(2) |
1.0 |
|
| execveat(2) |
3.19 |
|
| exit(2) |
1.0 |
|
| exit_group(2) |
2.6 |
|
| faccessat(2) |
2.6.16 |
|
| fadvise64(2) |
2.6 |
|
| . |
|
|
| fadvise64_64(2) |
2.6 |
|
| fallocate(2) |
2.6.23 |
|
| fanotify_init(2) |
2.6.37 |
|
| fanotify_mark(2) |
2.6.37 |
|
| . |
|
|
| . |
|
|
| fchdir(2) |
1.0 |
|
| fchmod(2) |
1.0 |
|
| fchmodat(2) |
2.6.16 |
|
| fchown(2) |
1.0 |
|
| fchown32(2) |
2.4 |
|
| fchownat(2) |
2.6.16 |
|
| fcntl(2) |
1.0 |
|
| fcntl64(2) |
2.4 |
|
| fdatasync(2) |
2.0 |
|
| fgetxattr(2) |
2.6; 2.4.18 |
|
| finit_module(2) |
3.8 |
|
| flistxattr(2) |
2.6; 2.4.18 |
|
| flock(2) |
2.0 |
|
| fork(2) |
1.0 |
|
| free_hugepages(2) |
2.5.36 |
Removed in 2.5.44 |
| fremovexattr(2) |
2.6; 2.4.18 |
|
| fsconfig(2) |
5.2 |
|
| fsetxattr(2) |
2.6; 2.4.18 |
|
| fsmount(2) |
5.2 |
|
| fsopen(2) |
5.2 |
|
| fspick(2) |
5.2 |
|
| fstat(2) |
1.0 |
|
| fstat64(2) |
2.4 |
|
| fstatat64(2) |
2.6.16 |
|
| fstatfs(2) |
1.0 |
|
| fstatfs64(2) |
2.6 |
|
| fsync(2) |
1.0 |
|
| ftruncate(2) |
1.0 |
|
| ftruncate64(2) |
2.4 |
|
| futex(2) |
2.6 |
|
| futimesat(2) |
2.6.16 |
|
| get_kernel_syms(2) |
1.0 |
Removed in 2.6 |
| get_mempolicy(2) |
2.6.6 |
|
| get_robust_list(2) |
2.6.17 |
|
| get_thread_area(2) |
2.6 |
|
| . |
|
|
| get_tls(2) |
4.15 |
ARM OABI only, has __ARM_NR prefix |
| getcpu(2) |
2.6.19 |
|
| getcwd(2) |
2.2 |
|
| getdents(2) |
2.0 |
|
| getdents64(2) |
2.4 |
|
| . |
|
|
| getdomainname(2) |
2.2 |
SPARC, SPARC64; available as osf_getdomainname(2) on Alpha since
Linux 2.0 |
| . |
|
|
| getdtablesize(2) |
2.0 |
SPARC (removed in 2.6.26), available on Alpha as
osf_getdtablesize(2) |
| getegid(2) |
1.0 |
|
| getegid32(2) |
2.4 |
|
| geteuid(2) |
1.0 |
|
| geteuid32(2) |
2.4 |
|
| getgid(2) |
1.0 |
|
| getgid32(2) |
2.4 |
|
| getgroups(2) |
1.0 |
|
| getgroups32(2) |
2.4 |
|
| . |
|
|
| gethostname(2) |
2.0 |
Alpha, was available on SPARC up to Linux 2.6.26 |
| getitimer(2) |
1.0 |
|
| getpeername(2) |
2.0 |
See notes on socketcall(2) |
| getpagesize(2) |
2.0 |
Not on x86 |
| getpgid(2) |
1.0 |
|
| getpgrp(2) |
1.0 |
|
| getpid(2) |
1.0 |
|
| getppid(2) |
1.0 |
|
| getpriority(2) |
1.0 |
|
| getrandom(2) |
3.17 |
|
| getresgid(2) |
2.2 |
|
| getresgid32(2) |
2.4 |
|
| getresuid(2) |
2.2 |
|
| getresuid32(2) |
2.4 |
|
| getrlimit(2) |
1.0 |
|
| getrusage(2) |
1.0 |
|
| getsid(2) |
2.0 |
|
| getsockname(2) |
2.0 |
See notes on socketcall(2) |
| getsockopt(2) |
2.0 |
See notes on socketcall(2) |
| gettid(2) |
2.4.11 |
|
| gettimeofday(2) |
1.0 |
|
| getuid(2) |
1.0 |
|
| getuid32(2) |
2.4 |
|
| getunwind(2) |
2.4.8 |
IA-64 only; deprecated |
| getxattr(2) |
2.6; 2.4.18 |
|
| getxgid(2) |
2.0 |
Alpha only; see NOTES |
| getxpid(2) |
2.0 |
Alpha only; see NOTES |
| getxuid(2) |
2.0 |
Alpha only; see NOTES |
| init_module(2) |
1.0 |
|
| inotify_add_watch(2) |
2.6.13 |
|
| inotify_init(2) |
2.6.13 |
|
| inotify_init1(2) |
2.6.27 |
|
| inotify_rm_watch(2) |
2.6.13 |
|
| io_cancel(2) |
2.6 |
|
| io_destroy(2) |
2.6 |
|
| io_getevents(2) |
2.6 |
|
| io_pgetevents(2) |
4.18 |
|
| io_setup(2) |
2.6 |
|
| io_submit(2) |
2.6 |
|
| io_uring_enter(2) |
5.1 |
|
| io_uring_register(2) |
5.1 |
|
| io_uring_setup(2) |
5.1 |
|
| ioctl(2) |
1.0 |
|
| ioperm(2) |
1.0 |
|
| iopl(2) |
1.0 |
|
| ioprio_get(2) |
2.6.13 |
|
| ioprio_set(2) |
2.6.13 |
|
| ipc(2) |
1.0 |
|
| . |
|
|
| kcmp(2) |
3.5 |
|
| kern_features(2) |
3.7 |
SPARC64 only |
| . |
|
|
| . |
|
|
| kexec_file_load(2) |
3.17 |
|
| kexec_load(2) |
2.6.13 |
|
| . |
|
|
| . |
|
|
| keyctl(2) |
2.6.10 |
|
| kill(2) |
1.0 |
|
| lchown(2) |
1.0 |
See chown(2) for version details |
| lchown32(2) |
2.4 |
|
| lgetxattr(2) |
2.6; 2.4.18 |
|
| link(2) |
1.0 |
|
| linkat(2) |
2.6.16 |
|
| listen(2) |
2.0 |
See notes on socketcall(2) |
| listxattr(2) |
2.6; 2.4.18 |
|
| llistxattr(2) |
2.6; 2.4.18 |
|
| lookup_dcookie(2) |
2.6 |
|
| lremovexattr(2) |
2.6; 2.4.18 |
|
| lseek(2) |
1.0 |
|
| lsetxattr(2) |
2.6; 2.4.18 |
|
| lstat(2) |
1.0 |
|
| lstat64(2) |
2.4 |
|
| madvise(2) |
2.4 |
|
| mbind(2) |
2.6.6 |
|
| memory_ordering(2) |
2.2 |
SPARC64 only |
| . |
|
|
| . |
|
|
| metag_get_tls(2) |
3.9 |
Metag only (port removed in Linux 4.17) |
| metag_set_fpu_flags(2) |
3.9 |
Metag only (port removed in Linux 4.17) |
| metag_set_tls(2) |
3.9 |
Metag only (port removed in Linux 4.17) |
| metag_setglobalbit(2) |
3.9 |
Metag only (port removed in Linux 4.17) |
| membarrier(2) |
3.17 |
|
| memfd_create(2) |
3.17 |
|
| migrate_pages(2) |
2.6.16 |
|
| mincore(2) |
2.4 |
|
| mkdir(2) |
1.0 |
|
| mkdirat(2) |
2.6.16 |
|
| mknod(2) |
1.0 |
|
| mknodat(2) |
2.6.16 |
|
| mlock(2) |
2.0 |
|
| mlock2(2) |
4.4 |
|
| mlockall(2) |
2.0 |
|
| mmap(2) |
1.0 |
|
| mmap2(2) |
2.4 |
|
| modify_ldt(2) |
1.0 |
|
| mount(2) |
1.0 |
|
| move_mount(2) |
5.2 |
|
| move_pages(2) |
2.6.18 |
|
| mprotect(2) |
1.0 |
|
| mq_getsetattr(2) |
2.6.6 |
|
| . |
|
|
| mq_notify(2) |
2.6.6 |
|
| mq_open(2) |
2.6.6 |
|
| mq_timedreceive(2) |
2.6.6 |
|
| mq_timedsend(2) |
2.6.6 |
|
| mq_unlink(2) |
2.6.6 |
|
| mremap(2) |
2.0 |
|
| msgctl(2) |
2.0 |
See notes on ipc(2) |
| msgget(2) |
2.0 |
See notes on ipc(2) |
| msgrcv(2) |
2.0 |
See notes on ipc(2) |
| msgsnd(2) |
2.0 |
See notes on ipc(2) |
| msync(2) |
2.0 |
|
| . |
|
|
| . |
|
|
| munlock(2) |
2.0 |
|
| munlockall(2) |
2.0 |
|
| munmap(2) |
1.0 |
|
| name_to_handle_at(2) |
2.6.39 |
|
| nanosleep(2) |
2.0 |
|
| . |
|
|
| newfstatat(2) |
2.6.16 |
See stat(2) |
| nfsservctl(2) |
2.2 |
Removed in 3.1 |
| nice(2) |
1.0 |
|
| old_adjtimex(2) |
2.0 |
Alpha only; see NOTES |
| old_getrlimit(2) |
2.4 |
Old variant of getrlimit(2) that used a different value for
RLIM_INFINITY |
| oldfstat(2) |
1.0 |
|
| oldlstat(2) |
1.0 |
|
| oldolduname(2) |
1.0 |
|
| oldstat(2) |
1.0 |
|
| oldumount(2) |
2.4.116 |
Name of the old umount(2) syscall on Alpha |
| olduname(2) |
1.0 |
|
| open(2) |
1.0 |
|
| open_by_handle_at(2) |
2.6.39 |
|
| open_tree(2) |
5.2 |
|
| openat(2) |
2.6.16 |
|
| openat2(2) |
5.6 |
|
| . |
|
|
| or1k_atomic(2) |
3.1 |
OpenRISC 1000 only |
| pause(2) |
1.0 |
|
| pciconfig_iobase(2) |
2.2.15; 2.4 |
Not on x86 |
| . |
|
|
| pciconfig_read(2) |
2.0.26; 2.2 |
Not on x86 |
| . |
|
|
| pciconfig_write(2) |
2.0.26; 2.2 |
Not on x86 |
| . |
|
|
| perf_event_open(2) |
2.6.31 |
Was perf_counter_open() in 2.6.31; renamed in 2.6.32 |
| personality(2) |
1.2 |
|
| perfctr(2) |
2.2 |
SPARC only; removed in 2.6.34 |
| . |
|
|
| perfmonctl(2) |
2.4 |
IA-64 only |
| pidfd_getfd(2) |
5.6 |
|
| pidfd_send_signal(2) |
5.1 |
|
| pidfd_open(2) |
5.3 |
|
| pipe(2) |
1.0 |
|
| pipe2(2) |
2.6.27 |
|
| pivot_root(2) |
2.4 |
|
| pkey_alloc(2) |
4.8 |
|
| pkey_free(2) |
4.8 |
|
| pkey_mprotect(2) |
4.8 |
|
| poll(2) |
2.0.36; 2.2 |
|
| ppoll(2) |
2.6.16 |
|
| prctl(2) |
2.2 |
|
| pread(2) |
|
Used for pread64(2) on AVR32 (port removed in Linux 4.12) and
Blackfin (port removed in Linux 4.17) |
| pread64(2) |
|
Added as "pread" in 2.2; renamed "pread64" in
2.6 |
| preadv(2) |
2.6.30 |
|
| preadv2(2) |
4.6 |
|
| prlimit64(2) |
2.6.36 |
|
| process_vm_readv(2) |
3.2 |
|
| process_vm_writev(2) |
3.2 |
|
| pselect6(2) |
2.6.16 |
|
| . |
|
|
| ptrace(2) |
1.0 |
|
| pwrite(2) |
|
Used for pwrite64(2) on AVR32 (port removed in Linux 4.12) and
Blackfin (port removed in Linux 4.17) |
| pwrite64(2) |
|
Added as "pwrite" in 2.2; renamed "pwrite64" in
2.6 |
| pwritev(2) |
2.6.30 |
|
| pwritev2(2) |
4.6 |
|
| query_module(2) |
2.2 |
Removed in 2.6 |
| quotactl(2) |
1.0 |
|
| read(2) |
1.0 |
|
| readahead(2) |
2.4.13 |
|
| readdir(2) |
1.0 |
|
| . |
|
|
| readlink(2) |
1.0 |
|
| readlinkat(2) |
2.6.16 |
|
| readv(2) |
2.0 |
|
| reboot(2) |
1.0 |
|
| recv(2) |
2.0 |
See notes on socketcall(2) |
| recvfrom(2) |
2.0 |
See notes on socketcall(2) |
| recvmsg(2) |
2.0 |
See notes on socketcall(2) |
| recvmmsg(2) |
2.6.33 |
|
| remap_file_pages(2) |
2.6 |
Deprecated since 3.16 |
| removexattr(2) |
2.6; 2.4.18 |
|
| rename(2) |
1.0 |
|
| renameat(2) |
2.6.16 |
|
| renameat2(2) |
3.15 |
|
| request_key(2) |
2.6.10 |
|
| restart_syscall(2) |
2.6 |
|
| . |
|
|
| riscv_flush_icache(2) |
4.15 |
RISC-V only |
| rmdir(2) |
1.0 |
|
| rseq(2) |
4.18 |
|
| rt_sigaction(2) |
2.2 |
|
| rt_sigpending(2) |
2.2 |
|
| rt_sigprocmask(2) |
2.2 |
|
| rt_sigqueueinfo(2) |
2.2 |
|
| rt_sigreturn(2) |
2.2 |
|
| rt_sigsuspend(2) |
2.2 |
|
| rt_sigtimedwait(2) |
2.2 |
|
| rt_tgsigqueueinfo(2) |
2.6.31 |
|
| rtas(2) |
2.6.2 |
PowerPC/PowerPC64 only |
| s390_runtime_instr(2) |
3.7 |
s390 only |
| s390_pci_mmio_read(2) |
3.19 |
s390 only |
| s390_pci_mmio_write(2) |
3.19 |
s390 only |
| s390_sthyi(2) |
4.15 |
s390 only |
| s390_guarded_storage(2) |
4.12 |
s390 only |
| sched_get_affinity(2) |
2.6 |
Name of sched_getaffinity(2) on SPARC and SPARC64 |
| sched_get_priority_max(2) |
2.0 |
|
| sched_get_priority_min(2) |
2.0 |
|
| sched_getaffinity(2) |
2.6 |
|
| sched_getattr(2) |
3.14 |
|
| sched_getparam(2) |
2.0 |
|
| sched_getscheduler(2) |
2.0 |
|
| sched_rr_get_interval(2) |
2.0 |
|
| sched_set_affinity(2) |
2.6 |
Name of sched_setaffinity(2) on SPARC and SPARC64 |
| sched_setaffinity(2) |
2.6 |
|
| sched_setattr(2) |
3.14 |
|
| sched_setparam(2) |
2.0 |
|
| sched_setscheduler(2) |
2.0 |
|
| sched_yield(2) |
2.0 |
|
| seccomp(2) |
3.17 |
|
| select(2) |
1.0 |
|
| semctl(2) |
2.0 |
See notes on ipc(2) |
| semget(2) |
2.0 |
See notes on ipc(2) |
| semop(2) |
2.0 |
See notes on ipc(2) |
| semtimedop(2) |
2.6; 2.4.22 |
|
| send(2) |
2.0 |
See notes on socketcall(2) |
| sendfile(2) |
2.2 |
|
| sendfile64(2) |
2.6; 2.4.19 |
|
| sendmmsg(2) |
3.0 |
|
| sendmsg(2) |
2.0 |
See notes on socketcall(2) |
| sendto(2) |
2.0 |
See notes on socketcall(2) |
| set_mempolicy(2) |
2.6.6 |
|
| set_robust_list(2) |
2.6.17 |
|
| set_thread_area(2) |
2.6 |
|
| set_tid_address(2) |
2.6 |
|
| set_tls(2) |
2.6.11 |
ARM OABI/EABI only (constant has __ARM_NR prefix) |
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| setdomainname(2) |
1.0 |
|
| setfsgid(2) |
1.2 |
|
| setfsgid32(2) |
2.4 |
|
| setfsuid(2) |
1.2 |
|
| setfsuid32(2) |
2.4 |
|
| setgid(2) |
1.0 |
|
| setgid32(2) |
2.4 |
|
| setgroups(2) |
1.0 |
|
| setgroups32(2) |
2.4 |
|
| . |
|
|
| sethae(2) |
2.0 |
Alpha only; see NOTES |
| sethostname(2) |
1.0 |
|
| setitimer(2) |
1.0 |
|
| setns(2) |
3.0 |
|
| setpgid(2) |
1.0 |
|
| setpgrp(2) |
2.0 |
Alternative name for setpgid(2) on Alpha |
| setpriority(2) |
1.0 |
|
| setregid(2) |
1.0 |
|
| setregid32(2) |
2.4 |
|
| setresgid(2) |
2.2 |
|
| setresgid32(2) |
2.4 |
|
| setresuid(2) |
2.2 |
|
| setresuid32(2) |
2.4 |
|
| setreuid(2) |
1.0 |
|
| setreuid32(2) |
2.4 |
|
| setrlimit(2) |
1.0 |
|
| setsid(2) |
1.0 |
|
| setsockopt(2) |
2.0 |
See notes on socketcall(2) |
| settimeofday(2) |
1.0 |
|
| setuid(2) |
1.0 |
|
| setuid32(2) |
2.4 |
|
| setup(2) |
1.0 |
Removed in 2.2 |
| setxattr(2) |
2.6; 2.4.18 |
|
| sgetmask(2) |
1.0 |
|
| shmat(2) |
2.0 |
See notes on ipc(2) |
| shmctl(2) |
2.0 |
See notes on ipc(2) |
| shmdt(2) |
2.0 |
See notes on ipc(2) |
| shmget(2) |
2.0 |
See notes on ipc(2) |
| shutdown(2) |
2.0 |
See notes on socketcall(2) |
| sigaction(2) |
1.0 |
|
| sigaltstack(2) |
2.2 |
|
| signal(2) |
1.0 |
|
| signalfd(2) |
2.6.22 |
|
| signalfd4(2) |
2.6.27 |
|
| sigpending(2) |
1.0 |
|
| sigprocmask(2) |
1.0 |
|
| sigreturn(2) |
1.0 |
|
| sigsuspend(2) |
1.0 |
|
| socket(2) |
2.0 |
See notes on socketcall(2) |
| socketcall(2) |
1.0 |
|
| . |
|
|
| socketpair(2) |
2.0 |
See notes on socketcall(2) |
| . |
|
|
| spill(2) |
2.6.13 |
Xtensa only |
| splice(2) |
2.6.17 |
|
| spu_create(2) |
2.6.16 |
PowerPC/PowerPC64 only |
| spu_run(2) |
2.6.16 |
PowerPC/PowerPC64 only |
| sram_alloc(2) |
2.6.22 |
Blackfin (port removed in Linux 4.17) |
| sram_free(2) |
2.6.22 |
Blackfin (port removed in Linux 4.17) |
| ssetmask(2) |
1.0 |
|
| stat(2) |
1.0 |
|
| stat64(2) |
2.4 |
|
| statfs(2) |
1.0 |
|
| statfs64(2) |
2.6 |
|
| statx(2) |
4.11 |
|
| stime(2) |
1.0 |
|
| subpage_prot(2) |
2.6.25 |
PowerPC/PowerPC64 only |
| swapcontext(2) |
2.6.3 |
PowerPC/PowerPC64 only |
| . |
|
|
| switch_endian(2) |
4.1 |
PowerPC64 only |
| swapcontext(2) |
2.6.3 |
PowerPC only |
| swapoff(2) |
1.0 |
|
| swapon(2) |
1.0 |
|
| symlink(2) |
1.0 |
|
| symlinkat(2) |
2.6.16 |
|
| sync(2) |
1.0 |
|
| sync_file_range(2) |
2.6.17 |
|
| sync_file_range2(2) |
2.6.22 |
|
| . |
|
|
| . |
|
|
| . |
|
|
| syncfs(2) |
2.6.39 |
|
| sys_debug_setcontext(2) |
2.6.11 |
PowerPC only |
| syscall(2) |
1.0 |
Still available on ARM OABI and MIPS O32 ABI |
| sysfs(2) |
1.2 |
|
| sysinfo(2) |
1.0 |
|
| syslog(2) |
1.0 |
|
| . |
|
|
| sysmips(2) |
2.6.0 |
MIPS only |
| tee(2) |
2.6.17 |
|
| tgkill(2) |
2.6 |
|
| time(2) |
1.0 |
|
| timer_create(2) |
2.6 |
|
| timer_delete(2) |
2.6 |
|
| timer_getoverrun(2) |
2.6 |
|
| timer_gettime(2) |
2.6 |
|
| timer_settime(2) |
2.6 |
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| . |
|
|
| timerfd_create(2) |
2.6.25 |
|
| timerfd_gettime(2) |
2.6.25 |
|
| timerfd_settime(2) |
2.6.25 |
|
| times(2) |
1.0 |
|
| tkill(2) |
2.6; 2.4.22 |
|
| truncate(2) |
1.0 |
|
| truncate64(2) |
2.4 |
|
| ugetrlimit(2) |
2.4 |
|
| umask(2) |
1.0 |
|
| umount(2) |
1.0 |
|
| . |
|
|
| umount2(2) |
2.2 |
|
| . |
|
|
| uname(2) |
1.0 |
|
| unlink(2) |
1.0 |
|
| unlinkat(2) |
2.6.16 |
|
| unshare(2) |
2.6.16 |
|
| uselib(2) |
1.0 |
|
| ustat(2) |
1.0 |
|
| userfaultfd(2) |
4.3 |
|
| usr26(2) |
2.4.8.1 |
ARM OABI only |
| usr32(2) |
2.4.8.1 |
ARM OABI only |
| utime(2) |
1.0 |
|
| utimensat(2) |
2.6.22 |
|
| utimes(2) |
2.2 |
|
| utrap_install(2) |
2.2 |
SPARC64 only |
| . |
|
|
| . |
|
|
| vfork(2) |
2.2 |
|
| vhangup(2) |
1.0 |
|
| vm86old(2) |
1.0 |
Was "vm86"; renamed in 2.0.28/2.2 |
| vm86(2) |
2.0.28; 2.2 |
|
| vmsplice(2) |
2.6.17 |
|
| wait4(2) |
1.0 |
|
| waitid(2) |
2.6.10 |
|
| waitpid(2) |
1.0 |
|
| write(2) |
1.0 |
|
| writev(2) |
2.0 |
|
| . |
|
|
| xtensa(2) |
2.6.13 |
Xtensa only |
On many platforms, including x86-32, socket calls are all multiplexed (via glibc
wrapper functions) through
socketcall(2) and similarly System V
IPC calls are multiplexed through
ipc(2).
Although slots are reserved for them in the system call table, the following
system calls are not implemented in the standard kernel:
afs_syscall(2),
break(2),
ftime(2),
getpmsg(2),
gtty(2),
idle(2),
lock(2),
madvise1(2),
mpx(2),
phys(2),
prof(2),
profil(2),
putpmsg(2),
security(2),
stty(2),
tuxcall(2),
ulimit(2), and
vserver(2) (see also
unimplemented(2)).
However,
ftime(3),
profil(3), and
ulimit(3) exist as
library routines. The slot for
phys(2) is in use since kernel 2.1.116
for
umount(2);
phys(2) will never be implemented. The
getpmsg(2) and
putpmsg(2) calls are for kernels patched to
support STREAMS, and may never be in the standard kernel.
There was briefly
set_zone_reclaim(2), added in Linux 2.6.13, and removed
in 2.6.16; this system call was never available to user space.
Roughly speaking, the code belonging to the system call with number __NR_xxx
defined in
/usr/include/asm/unistd.h can be found in the Linux kernel
source in the routine
sys_xxx(). 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
operating-system emulation, such as 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, certain
architectures (notably, longstanding 32-bit architectures such as i386) now
have various groups of related system calls (e.g.,
truncate(2) and
truncate64(2)) which perform similar tasks, but which vary in details
such as the size of their arguments. (As noted earlier, applications are
generally unaware of this: the glibc wrapper functions do some work to ensure
that the right system call is invoked, and that ABI compatibility is preserved
for old binaries.) Examples of systems calls that exist in multiple versions
are the following:
- *
- By now there are three different versions of stat(2):
sys_stat() (slot __NR_oldstat), sys_newstat() (slot
__NR_stat), and sys_stat64() (slot __NR_stat64), with
the last being the most current. A similar story applies for
lstat(2) and fstat(2).
- *
- Similarly, the defines __NR_oldolduname, __NR_olduname, and
__NR_uname refer to the routines sys_olduname(),
sys_uname() and sys_newuname().
- *
- In Linux 2.0, a new version of vm86(2) appeared, with the old and
the new kernel routines being named sys_vm86old() and
sys_vm86().
- *
- In Linux 2.4, a new version of getrlimit(2) appeared, with the old
and the new kernel routines being named sys_old_getrlimit() (slot
__NR_getrlimit) and sys_getrlimit() (slot
__NR_ugetrlimit).
- *
- Linux 2.4 increased the size of user and group IDs from 16 to 32 bits. To
support this change, a range of system calls were added (e.g.,
chown32(2), getuid32(2), getgroups32(2),
setresuid32(2)), superseding earlier calls of the same name without
the "32" suffix.
- *
- 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: fcntl64(2),
getdents64(2), stat64(2), statfs64(2),
truncate64(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.
- On newer platforms that only have 64-bit file access and 32-bit UIDs/GIDs
(e.g., alpha, ia64, s390x, x86-64), there is just a single version of the
UID/GID and file access system calls. On platforms (typically, 32-bit
platforms) where the *64 and *32 calls exist, the other versions are
obsolete.
- *
- The rt_sig* calls were added in kernel 2.2 to support the addition
of real-time signals (see signal(7)). These system calls supersede
the older system calls of the same name without the "rt_"
prefix.
- *
- The select(2) and mmap(2) system calls use five or more
arguments, which caused problems in the way argument passing on the i386
used to be set up. Thus, while other architectures have
sys_select() and sys_mmap() corresponding to
__NR_select and __NR_mmap, on i386 one finds
old_select() and old_mmap() (routines that use a pointer to
an argument block) instead. These days passing five arguments is not a
problem any more, and there is a __NR__newselect that corresponds
directly to sys_select() and similarly __NR_mmap2. s390x is
the only 64-bit architecture that has old_mmap().
- *
- getxgid(2) returns a pair of GID and effective GID via registers
r0 and r20; it is provided instead of getgid(2) and
getegid(2).
- *
- getxpid(2) returns a pair of PID and parent PID via registers
r0 and r20; it is provided instead of getpid(2) and
getppid(2).
- *
- old_adjtimex(2) is a variant of adjtimex(2) that uses
struct timeval32, for compatibility with OSF/1.
- *
- getxuid(2) returns a pair of GID and effective GID via registers
r0 and r20; it is provided instead of getuid(2) and
geteuid(2).
- *
- sethae(2) is used for configuring the Host Address Extension
register on low-cost Alphas in order to access address space beyond first
27 bits.
intro(2),
syscall(2),
unimplemented(2),
errno(3),
libc(7),
vdso(7)