Section 2 of the manual describes the Linux system calls. A system call is an entry point into the Linux kernel. Usually, system calls are not invoked directly: instead, most system calls have corresponding C library wrapper functions which perform the steps required (e.g., trapping to kernel mode) in order to invoke the system call. Thus, making a system call looks the same as invoking a normal library function.

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setsid
create session and set process group ID
setsockopt
getsockopt, setsockopt - get and set options on sockets
setsockopt
getsockopt , setsockopt — get and set options on sockets
settimeofday
gettimeofday, settimeofday - get / set time
settimeofday
gettimeofday , settimeofday — get/set date and time
setuid
set user identity
setuid
setuid , seteuid , setgid , setegid — set user and group ID
setuid32
setuid - set user identity
setup
setup devices and filesystems, mount root filesystem
setxattr
setxattr, lsetxattr, fsetxattr - set an extended attribute value
sgetmask
sgetmask, ssetmask - manipulation of signal mask (obsolete)
shm_open
shm_open , shm_unlink — shared memory object operations
shm_unlink
shm_open , shm_unlink — shared memory object operations
shmat
shmat, shmdt - System V shared memory operations
shmat
shmat , shmdt — attach or detach shared memory
shmctl
System V shared memory control
shmctl
shared memory control
shmdt
shmat, shmdt - System V shared memory operations
shmdt
shmat , shmdt — attach or detach shared memory
shmget
allocates a System V shared memory segment
shmget
obtain a shared memory identifier
shmop
shmat, shmdt - System V shared memory operations
shutdown
shut down part of a full-duplex connection
shutdown
disable sends and/or receives on a socket
sigaction
sigaction, rt_sigaction - examine and change a signal action
sigaction
software signal facilities
sigaltstack
set and/or get signal stack context
sigaltstack
set and/or get signal stack context
sigblock
sigsetmask , sigblock — manipulate current signal mask
sighold
sighold , sigignore , sigpause , sigrelse , sigset — legacy interface for signal management
sigignore
sighold , sigignore , sigpause , sigrelse , sigset — legacy interface for signal management
sigmask
sigsetmask , sigblock — manipulate current signal mask
signal
ANSI C signal handling
signalfd
create a file descriptor for accepting signals
signalfd4
signalfd - create a file descriptor for accepting signals
sigpause
sighold , sigignore , sigpause , sigrelse , sigset — legacy interface for signal management
sigpending
sigpending, rt_sigpending - examine pending signals
sigpending
get pending signals
sigprocmask
sigprocmask, rt_sigprocmask - examine and change blocked signals
sigprocmask
manipulate current signal mask
sigqueue
queue a signal to a process (REALTIME)
sigrelse
sighold , sigignore , sigpause , sigrelse , sigset — legacy interface for signal management
sigreturn
sigreturn, rt_sigreturn - return from signal handler and cleanup stack frame
sigreturn
return from signal
sigset
sighold , sigignore , sigpause , sigrelse , sigset — legacy interface for signal management
sigsetmask
sigsetmask , sigblock — manipulate current signal mask
sigstack
set and/or get signal stack context
sigsuspend
sigsuspend, rt_sigsuspend - wait for a signal
sigsuspend
atomically release blocked signals and wait for interrupt
sigtimedwait
sigwaitinfo, sigtimedwait, rt_sigtimedwait - synchronously wait for queued signals
sigtimedwait
sigtimedwait , sigwaitinfo — wait for queued signals (REALTIME)
sigvec
software signal facilities
sigwait
select a set of signals
sigwaitinfo
sigwaitinfo, sigtimedwait, rt_sigtimedwait - synchronously wait for queued signals
sigwaitinfo
sigtimedwait , sigwaitinfo — wait for queued signals (REALTIME)
socket
create an endpoint for communication
socket
create an endpoint for communication
socketcall
socket system calls
socketpair
create a pair of connected sockets
socketpair
create a pair of connected sockets
space
piecewise polynomial finite element space (rheolef-7.2)
splice
splice data to/from a pipe
spu_create
create a new spu context
spu_run
execute an SPU context
ssetmask
sgetmask, ssetmask - manipulation of signal mask (obsolete)
stat
stat, fstat, lstat, fstatat - get file status
stat
stat , lstat , fstat , fstatat — get file status
stat64
stat, fstat, lstat, fstatat - get file status
statfs
statfs, fstatfs - get filesystem statistics
statfs
get file system statistics
statfs64
statfs, fstatfs - get filesystem statistics
statx
get file status (extended)
stime
set time
stty
afs_syscall, break, fattach, fdetach, ftime, getmsg, getpmsg, gtty, isastream, lock, madvise1, mpx, prof, profil, putmsg, putpmsg, security, stty, tuxcall, ulimit, vserver - unimplemented system calls
subpage_prot
define a subpage protection for an address range
swapoff
swapon, swapoff - start/stop swapping to file/device
swapoff
swapon , swapoff — control devices for interleaved paging/swapping
swapon
swapon, swapoff - start/stop swapping to file/device
swapon
swapon , swapoff — control devices for interleaved paging/swapping
symlink
symlink, symlinkat - make a new name for a file
symlink
symlink , symlinkat — make symbolic link to a file
symlinkat
symlink, symlinkat - make a new name for a file
symlinkat
symlink , symlinkat — make symbolic link to a file
sync
sync, syncfs - commit filesystem caches to disk
sync
schedule file system updates
sync_file_range
sync a file segment with disk
sync_file_range2
sync_file_range - sync a file segment with disk
syncfs
sync, syncfs - commit filesystem caches to disk
sysarch
architecture-dependent system call
syscall
indirect system call
syscall
syscall , __syscall — indirect system call
syscalls
Linux system calls
sysctl
read/write system parameters
sysfs
get filesystem type information
sysinfo
return system information
syslog
syslog, klogctl - read and/or clear kernel message ring buffer; set console_loglevel
tee
duplicating pipe content
tensor
d-dimensional physical tensor (rheolef-7.2)
tensor3
d-dimensional physical third-order tensor (rheolef-7.2)
tensor4
d-dimensional physical fourth-order tensor (rheolef-7.2)