SIGKILL
From Wikipedia, the free encyclopedia
| Description: | Kill signal |
|---|---|
| Default action: | Abnormal termination of the process |
| SA_SIGINFO macros | |
| None | |
On POSIX-compliant platforms, SIGKILL is the signal sent to computer programs to cause them to terminate immediately. The symbolic constant for SIGKILL is defined in the header file signal.h. Symbolic signal names are used because signal numbers can vary across platforms, however on the vast majority of systems, SIGKILL is signal #9.
[edit] Etymology
SIG is a common prefix for signal names. KILL is computer jargon for the action of making a process terminate immediately.
[edit] Usage
When sent to a program, SIGKILL causes it to terminate immediately. Contrary to SIGTERM and SIGINT, this signal cannot be caught or ignored, and the receiving process cannot perform any clean-up upon receiving this signal.
- Zombie processes cannot be killed since they are already dead and waiting for their parent processes to reap them.
- Processes that are in the blocked state will not die until they wake up again.
- The init process is special: It does not get signals that it does not want to handle, and thus it can ignore SIGKILL.
- Because SIGKILL gives the process no opportunity to do cleanup operations on terminating, in most system shutdown procedures an attempt is first made to terminate processes using SIGTERM, before resorting to SIGKILL.
| POSIX Signals |
| SIGABRT | SIGALRM | SIGFPE | SIGHUP | SIGILL | SIGINT | SIGKILL | SIGPIPE | SIGQUIT | SIGSEGV | SIGTERM | SIGUSR1 | SIGUSR2 | SIGCHLD | SIGCONT | SIGSTOP | SIGTSTP | SIGTTIN | SIGTTOU | SIGBUS | SIGPOLL | SIGPROF | SIGSYS | SIGTRAP | SIGURG | SIGVTALRM | SIGXCPU | SIGXFSZ | Realtime Signals are user definable—SIGRTMIN+n through SIGRTMAX. |
| Common non-POSIX signals and synonyms |
| SIGIOT | SIGEMT | SIGSTKFLT | SIGIO | SIGCLD | SIGINFO | SIGPWR (SIGINFO) | SIGLOST | SIGWINCH | SIGUNUSED |
