Editing Signal (IPC) (section)

==Miscellaneous signals==
The following signals are not specified in the [[POSIX]] specification. They are, however, sometimes used on various systems.

; {{mono|{{vanchor|SIGEMT}}}}
: The SIGEMT signal is sent to a process when an '''em'''ulator '''t'''rap occurs. While an '''[[emulator]]''' usually means software that executes other programs, in this case it means a program executed a [[supervisor call]] instruction (EMT was the instruction for this purpose on the [[Digital Equipment Corporation|DEC]] [[PDP-11]] series of computers.)
; {{mono|{{vanchor|SIGINFO}}}}
: The SIGINFO signal is sent to a process when a status ('''info''') request is received from the controlling terminal.
; {{mono|{{vanchor|SIGPWR}}}}
: The SIGPWR signal is sent to a process when the system experiences a '''[[power failure]]'''.
; {{mono|{{vanchor|SIGLOST}}}}
: The SIGLOST signal is sent to a process when a file lock is '''lost'''.
; {{mono|{{vanchor|SIGSTKFLT}}}}
: The SIGSTKFLT signal is sent to a process when the coprocessor experiences a '''st'''ac'''k''' '''f'''au'''lt''' (i.e. popping when the stack is empty or pushing when it is full).<ref name="courier-mta.org">{{Cite web|url=https://manpages.courier-mta.org/htmlman7/signal.7.html|title=signal(7) — Linux manual pages|website=manpages.courier-mta.org|access-date=2018-11-22}}</ref> It is defined by, but not used on Linux, where a [[x87]] coprocessor stack fault will generate SIGFPE instead.<ref>{{cite web|url=https://stackoverflow.com/questions/9332864/linux-3-0-x86-64-when-is-sigstkflt-raised#comment51557777_9333099|title=Linux 3.0 x86_64: When is SIGSTKFLT raised?|website=Stack Overflow}}</ref>
; {{mono|{{vanchor|SIGUNUSED}}}}
: The SIGUNUSED signal is sent to a process when a system call with an '''unused''' system call number is made. It is synonymous with SIGSYS on most architectures.<ref name="courier-mta.org"/>
; {{mono|{{vanchor|SIGCLD}}}}
: The SIGCLD signal is synonymous with SIGCHLD.<ref name="courier-mta.org"/>