trap

Syntax

trap [COMMANDS] [SIGNALS ...]

When Bash receives a signal for which a trap has been set while waiting for a command to complete,
the trap will not be executed until the command completes.

Signals can be sent to your programs using the kill command or keyboard shortcuts(ie. Ctrl+C).

When Bash is waiting for an asynchronous command via the wait built-in,
the reception of a signal for which a trap has been set will cause the wait built-in to return immediately with an exit status greater than 128

 * The return status of the trap command itself is zero unless an invalid signal specification is encountered.

SIGNALS

• EXIT                 # 所有的 exit. ie. exit 0 | exit 1 ...
• SIGHUP            # 1, Hangup
• SIGINT             # 2, Ctrl+C
• SIGTERM          # 15
• SIGKILL            # 9. Can not be caught
• SIGTSTP           # Ctrl+Z
• DEBUG
• SIGUSR1          # "user"-defined signal => you can use however you like

Example

1) Run Script when press "Ctrl+C"

#!/bin/bash

function cleanup(){
    echo 'Press "Ctrl+C"'
}

trap cleanup SIGINT

ping 8.8.8.8
# OUTPUT 'Press "Ctrl+C"'
ping 8.8.4.4

2) script exit

#!/bin/bash

[email protected]

function mail2admin(){
        echo "Exit Code: $?"
        echo "Send mail to: $ADMIN"
}

trap mail2admin EXIT

exit 1