Bash Signal Processing

Bash processing signal

Send Signal

Kill

Format: kill[-s Sigspec |-n signum |-sigspec] [PID | jobspec] ...

You can send a process with a process number of PID, or you can send a process with the job number Jobspec

Sigspec can be either a signal number or a signal name, and the signal name can be no sig

The KILL command sends the SIGTERM signal by default, and the process that receives the sigterm signal ends the run

Terminal, CTRL + C sends int signal to foreground process, process exits, exit status is 130, add 128 for signal number

Processing signal

Establishing a signal callback function

Trapcmd signal1 signal2 Signal3 ...

CMD can be a sequence of commands or a function's name, or it can be empty, which will perform the default behavior

Signals of interest to shell script programming

Signal	Corresponding ID	Behavior	Meaning
SIGHUP	1	Term	hangupdetected on controlling terminal
SIGINT	2	Term	Interruptfrom keyboard
Sigquit	3	Core	Quitfrom keyboard
SIGKILL	9	Term	Killsignal
Sigalrm	14	Term	Timersignal
SIGTERM	15	Term	Terminationsignal

The shell script has a false signal 0, which is generated at exit and can be used to define a function for this signal to perform certain actions at the end of the script

Define the operation for the same signal multiple times, whichever is the last

Ignore signal

Use an empty string or colon in the trap to line.

Trap ' 2//Note the existence of quotation marks

Set timer

In fact, set up a daemon in the background to send sigalarm signals to the process after a certain event of sleep.

Way: Sleep$time && kill-s $$ &

This command generates a sleep process from the bash subprocess after the bash subprocess.

Notice the sequence of killing process when unregistering the timer, kill the parent process rashly, can't find the child process OH

This article is from the "No Front" blog, please be sure to keep this source http://qianyang.blog.51cto.com/7130735/1620558

Bash Signal Processing