Shell Signal capture Command trap

Trap command

tarpThe command is used to perform the action after the specified signal is received, usually in order to complete the cleanup when the shell script is interrupted. For example:
When the script is pressed at execution time CTRL+c , "program exit ..." is displayed and exits ( CTRL+c the signal is SIGINT)

#!/bin/bashtrap "ehco ‘program exit...‘; exit 2" SIGINT....

Signal

Common signals

signal name	signal number
sigint	2
sigquit	3
sigfpe	8	In the event of fatal arithmetic Is emitted when an operation is wrong. This includes not only floating-point arithmetic errors, but also all other arithmetic errors such as overflow and divisor 0.
sigkill	9
sigalrm	14	clock timing signal , the actual time or clock time is calculated. The alarm function uses this signal. SIGTERM

Capture Signal

• Command syntax for trap:

  shell trap command signal
  This command can be a Linux command, or a user-defined function. signalis the signal name or number of signals, you can specify multiple signals, separated by a space.

• trapCommon use in the shell

  • Execute command before script exits

  When the script is pressed at execution time CTRL+c , "program exit ..." is displayed and exits ( CTRL+c the signal is SIGINT)

  trap "ehco ‘program exit...‘; exit 2" SIGINT

  • Ignore signal

  Example: Ignoring SIGINT SIGQUIT SIGFPE such signals while the script is running

  trap ‘‘ 2 3 8

Shell Signal capture Command trap