Editing System call (section)

== Examples and tools ==
On [[Unix]], [[Unix-like]] and other [[POSIX]]-compliant operating systems, popular system calls are <code>[[open (system call)|open]]</code>, <code>[[read (system call)|read]]</code>, <code>[[write (system call)|write]]</code>, <code>[[close (system call)|close]]</code>, <code>[[wait (system call)|wait]]</code>, <code>[[exec (system call)|exec]]</code>, <code>[[fork (system call)|fork]]</code>, <code>[[exit (system call)|exit]]</code>, and <code>[[kill (system call)|kill]]</code>. Many modern operating systems have hundreds of system calls. For example, [[Linux kernel|Linux]] and [[OpenBSD]] each have over 300 different calls,<ref>{{cite web|url=http://man7.org/linux/man-pages/man2/syscalls.2.html|title=syscalls(2) - Linux manual page}}</ref><ref>{{cite web|url=http://bxr.su/OpenBSD/sys/kern/syscalls.c|website=BSD Cross Reference|author=OpenBSD|title=System call names (kern/syscalls.c)|date=2013-09-14}}</ref> [[NetBSD]] has close to 500,<ref>{{cite web|url=http://bxr.su/NetBSD/sys/kern/syscalls.c|website=BSD Cross Reference|author=NetBSD|title=System call names (kern/syscalls.c)|date=2013-10-17}}</ref> [[FreeBSD]] has over 500,<ref>{{cite web|url=http://fxr.watson.org/fxr/source/kern/syscalls.c|title=FreeBSD syscalls.c, the list of syscall names and IDs}}</ref> Windows has close to 2000, divided between win32k (graphical) and ntdll (core) system calls<ref>{{cite web|url=http://j00ru.vexillium.org/syscalls/win32k/32/|title=Windows WIN32K.SYS System Call Table (NT/2000/XP/2003/Vista/2008/7/8/10) |author=Mateusz "j00ru" Jurczyk | date=2017-11-05}}</ref> while [[Plan 9 from Bell Labs|Plan 9]] has 54.<ref>{{Cite web |title=sys.h |url=http://9p.io/sources/plan9/sys/src/libc/9syscall/sys.h |url-status=live |archive-url=https://web.archive.org/web/20230908211500/http://9p.io/sources/plan9/sys/src/libc/9syscall/sys.h |archive-date=Sep 8, 2023 |website=Plan 9 from Bell Labs |postscript=,}} the list of syscall names and IDs.</ref>

Tools such as [[strace]], [[ftrace]] and truss allow a process to execute from start and report all system calls the process invokes, or can attach to an already running process and intercept any system call made by the said process if the operation does not violate the permissions of the user. This special ability of the program is usually also implemented with system calls such as [[ptrace]] or system calls on files in [[procfs]].