Home > Article > Operation and Maintenance > What signals does linux have?
Linux signals include: 1. SIGHUP, used to shut down the process immediately, then re-read the configuration file and then restart; 2. SIGINT, the program abort signal, used to terminate the foreground process; 3. SIGQUIT, the program exits Signal; 4. SIGFPE, issued when a fatal arithmetic operation error occurs; 5. SIGKILL, used to end the program immediately; 6. SIGALRM, clock timing signal; 7. SIGTERM, signal to terminate the process normally; 8. SIGCONT; 9. SIGSTOP etc.
#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.
What are signals in Linux
The management of processes mainly refers to the closing and restarting of processes. When we generally close or restart a software, we close or restart its program, rather than directly operating the process. For example, to restart the apache service, generally use the command "service httpd restart" to restart the apache program.
So, can apache be shut down or restarted by directly managing the process? The answer is yes, then you have to rely on the signal of the process (Signal). We need to give the process a number and tell the process what we want it to do.
Signals are very important in the Linux operating system. Signals can be generated from the keyboard, generated by software conditions, or generated by calling hardware exceptions. There are a total of 64 signals in Linux generated from system function calls. Linux users can view them through kill -l, as follows
1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL 5) SIGTRAP 6) SIGABRT 7) SIGBUS 8) SIGFPE 9) SIGKILL 10) SIGUSR1 11) SIGSEGV 12) SIGUSR2 13) SIGPIPE 14) SIGALRM 15) SIGTERM 16) SIGSTKFLT 17) SIGCHLD 18) SIGCONT 19) SIGSTOP 20) SIGTSTP 21) SIGTTIN 22) SIGTTOU 23) SIGURG 24) SIGXCPU 25) SIGXFSZ 26) SIGVTALRM 27) SIGPROF 28) SIGWINCH 29) SIGIO 30) SIGPWR 31) SIGSYS 34) SIGRTMIN 35) SIGRTMIN+1 36) SIGRTMIN+2 37) SIGRTMIN+3 38) SIGRTMIN+4 39) SIGRTMIN+5 40) SIGRTMIN+6 41) SIGRTMIN+7 42) SIGRTMIN+8 43) SIGRTMIN+9 44) SIGRTMIN+10 45) SIGRTMIN+11 46) SIGRTMIN+12 47) SIGRTMIN+13 48) SIGRTMIN+14 49) SIGRTMIN+15 50) SIGRTMAX-14 51) SIGRTMAX-13 52) SIGRTMAX-12 53) SIGRTMAX-11 54) SIGRTMAX-10 55) SIGRTMAX-9 56) SIGRTMAX-8 57) SIGRTMAX-7 58) SIGRTMAX-6 59) SIGRTMAX-5 60) SIGRTMAX-4 61) SIGRTMAX-3 62) SIGRTMAX-2 63) SIGRTMAX-1 64) SIGRTMAX
The first 32 types are called unreliable signals, which are generally used after the software does not support queuing. The 32 types of signals known as reliable are generally used in hardware to support queuing.
Common signals in linux
Signal name | Explanation | |
---|---|---|
SIGHUP | This signal causes the process to shut down immediately. Then re-read the configuration file and restart | |
SIGINT | Program termination signal, used to terminate the foreground process. Equivalent to outputting Ctrl C shortcut key | |
SIGQUIT | Program exit signal (same as Ctrl \) | |
SIGFPE | Emitted when a fatal arithmetic error occurs. Including not only floating point operation errors, but also all other arithmetic operation errors such as overflow and division by 0 | |
SIGKILL | is used immediately End the program. This signal cannot be blocked, processed or ignored. Generally used to forcefully terminate the process | |
SIGALRM | Clock timing signal, which calculates the actual time or clock time. The alarm function uses this signal | |
SIGTERM | The signal to terminate the process normally, the default signal of the kill command. If a problem has occurred in the process, then this signal cannot terminate the process normally. Only then will we try the SIGKILL signal, which is signal 9 | |
SIGCONT | This signal allows the suspended process to resume execution. This signal cannot be blocked | |
SIGSTOP | This signal can suspend the foreground process, which is equivalent to entering the Ctrl Z shortcut key. This signal cannot be blocked |
Function | |
---|---|
Kill foreground process |
|
Suspend foreground process |
|
Terminate input, or exit shell |
|
Suspend output |
|
Resume output |
|
Discard output |
|
Clear screen |
The above is the detailed content of What signals does linux have?. For more information, please follow other related articles on the PHP Chinese website!