The trap is used to capture the signals under Linux __linux

In Linux, the Trap command is used primarily to receive signals and act, signals are sent asynchronously to a program's event, by default, a program can be terminated, and the Trap command prototype is as follows:

Trap command Signal

Signal is the signal received, the command is received by the signal to take action. The following are two simple signals.

Signal

Description

INT (2)

Ctrl + C

QUIT (3)

Ctrl + \

The sample code is as follows

[Root@localhost shell]# cat-n trap.sh 
     1	#!/bin/bash
     2	trap ' echo ' sorry! I Habe Trapped Ctrl + C "SIGINT sigterm
     3 echo This are	a test program
     4	count=1 5 while	[$coun T-le]
     6 do
     7		echo "LOOP # $count" 8 sleep		5
     9		count=$[$count + 1]
    10< C23/>done echo This is the "	test program
[root@localhost shell]# 

Run-Time CTRL + C results as shown in figure:

[Root@localhost shell]#./trap.sh This are 
a test program
loop #1
loop #2
^csorry! I Habe Trapped Ctrl + C
loop #3
loop #4
^csorry! I Habe Trapped Ctrl + C
loop #5
loop #6 loop
#7
loop #8
^csorry! I Habe Trapped Ctrl + C loop #9 Loop #10 This is the "the"
test program
[root@localhost shell]# 

If you want to capture the exit of the shell script, just add the exit signal to the trap command, and the code is as follows:

[Root@localhost shell]# cat-n trap.sh 
     1	#!/bin/bash
     2	trap ' echo ' sorry! I Habe Trapped Ctrl + C "" SIGINT sigterm
     3	trap "echo Goodbye" EXIT
     4 echo This are	a test program
     5	count=1
     6 while	[$count-le]
     7 does
     8		echo "LOOP # $count" 9 Sleep		5< c35/>10 count=$[$count + 1] One by one the echo this is the "the"
    test program
[Root@loca Lhost shell]# 

The results of the operation are as follows:

[Root@localhost shell]#./trap.sh This are 
a test program
LOOP #1
^csorry! I Habe Trapped Ctrl + C
LOOP #2
^csorry! I Habe Trapped Ctrl + C
LOOP #3
^csorry! I Habe Trapped Ctrl + C
loop #4
loop #5
loop #6
^csorry! I Habe Trapped Ctrl + C
LOOP #7
^csorry! I Habe Trapped Ctrl + C
loop #8
loop #9 Loop #10 This was the end of the "
test program
Goodbye
[ Root@localhost shell]# 

You can also remove the capture in the shell, as follows:

[Root@localhost shell]# cat-n trap.sh 
     1	#!/bin/bash
     2	trap ' echo ' sorry! I Habe Trapped Ctrl + C "" SIGINT sigterm
     3	trap "echo Goodbye" EXIT
     4 echo This are	a test program
     5	count=1
     6 while	[$count-le]
     7 does
     8		echo "LOOP # $count" 9 Sleep		1< C38/>10		count=$[$count + 1] One by one the echo this is the "the"	test program	TR Ap-exit	echo "	I just remove EXIT trap"

The exit capture is removed before the program ends, and the goodbye is eventually not exported:

[Root@localhost shell]#./trap.sh This are 
a test program
loop #1
loop #2
loop #3
loop #4
Loop #5 C6/>loop #6
loop #7 loop
#8
loop #9 Loop #10 This is the "end of" the
test program
	I just remove EXIT trap 
[Root@localhost shell]#