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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test
test-function in variational formulation (rheolef-7.2)
tgkill
tkill, tgkill - send a signal to a thread
thr_exit
terminate current thread
thr_kill
send signal to thread
thr_kill2
thr_kill — send signal to thread
thr_new
create new thread of execution
thr_self
return thread identifier for the calling thread
thr_set_name
set user-visible thread name
thr_suspend
suspend the calling thread
thr_wake
wake up the suspended thread
time
get time in seconds
timer_create
create a POSIX per-process timer
timer_create
create a per-process timer (REALTIME)
timer_delete
delete a POSIX per-process timer
timer_delete
delete a per-process timer (REALTIME)
timer_getoverrun
get overrun count for a POSIX per-process timer
timer_getoverrun
timer_getoverrun , timer_gettime , timer_settime — per-process timers (REALTIME)
timer_gettime
timer_settime, timer_gettime - arm/disarm and fetch state of POSIX per-process timer
timer_gettime
timer_getoverrun , timer_gettime , timer_settime — per-process timers (REALTIME)
timer_settime
timer_settime, timer_gettime - arm/disarm and fetch state of POSIX per-process timer
timer_settime
timer_getoverrun , timer_gettime , timer_settime — per-process timers (REALTIME)
timerfd_create
timerfd_create, timerfd_settime, timerfd_gettime - timers that notify via file descriptors
timerfd_gettime
timerfd_create, timerfd_settime, timerfd_gettime - timers that notify via file descriptors
timerfd_settime
timerfd_create, timerfd_settime, timerfd_gettime - timers that notify via file descriptors
times
get process times
tkill
tkill, tgkill - send a signal to a thread
tomcat10-instance-create
creates a Tomcat 10 instance
truncate
truncate, ftruncate - truncate a file to a specified length
truncate
truncate , ftruncate — truncate or extend a file to a specified length
truncate64
truncate, ftruncate - truncate a file to a specified length
tuxcall
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
ugetrlimit
getrlimit, setrlimit, prlimit - get/set resource limits
umask
set file mode creation mask
umask
set file creation mode mask
umount
umount, umount2 - unmount filesystem
umount2
umount, umount2 - unmount filesystem
uname
get name and information about current kernel
undelete
attempt to recover a deleted file
unimplemented
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
unlink
unlink, unlinkat - delete a name and possibly the file it refers to
unlink
unlink , unlinkat — remove directory entry
unlinkat
unlink, unlinkat - delete a name and possibly the file it refers to
unlinkat
unlink , unlinkat — remove directory entry
unmount
mount , nmount , unmount — mount or dismount a file system
unshare
disassociate parts of the process execution context
uselib
load shared library
userfaultfd
create a file descriptor for handling page faults in user space
ustat
get filesystem statistics
utime
utime, utimes - change file last access and modification times
utimensat
utimensat, futimens - change file timestamps with nanosecond precision
utimensat
futimens , utimensat — set file access and modification times
utimes
utime, utimes - change file last access and modification times
utimes
utimes , lutimes , futimes , futimesat — set file access and modification times
utrace
insert user record in ktrace log
uuidgen
generate universally unique identifiers
vfork
create a child process and block parent
vfork
create a new process without copying the address space
vhangup
virtually hangup the current terminal
vm86
vm86old, vm86 - enter virtual 8086 mode
vm86old
vm86old, vm86 - enter virtual 8086 mode
vmsplice
splice user pages to/from a pipe
vserver
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
wait
wait, waitpid, waitid - wait for process to change state
wait
wait , waitid , waitpid , wait3 , wait4 , wait6 — wait for processes to change status
wait3
wait3, wait4 - wait for process to change state, BSD style
wait3
wait , waitid , waitpid , wait3 , wait4 , wait6 — wait for processes to change status
wait4
wait3, wait4 - wait for process to change state, BSD style
wait4
wait , waitid , waitpid , wait3 , wait4 , wait6 — wait for processes to change status
wait6
wait , waitid , waitpid , wait3 , wait4 , wait6 — wait for processes to change status
waitid
wait, waitpid, waitid - wait for process to change state
waitid
wait , waitid , waitpid , wait3 , wait4 , wait6 — wait for processes to change status
waitpid
wait, waitpid, waitid - wait for process to change state
waitpid
wait , waitid , waitpid , wait3 , wait4 , wait6 — wait for processes to change status
write
write to a file descriptor
write
write , writev , pwrite , pwritev — write output
writev
readv, writev, preadv, pwritev, preadv2, pwritev2 - read or write data into multiple buffers
writev
write , writev , pwrite , pwritev — write output
xsi_sigpause
sighold , sigignore , sigpause , sigrelse , sigset — legacy interface for signal management