Usage of the Linux shell break, continue, exit, return

Break, continue, exit, return are generally used to control the direction of the loop

Start with a script description

For ((i=1;i<5;i++))

Do

If [$i-eq 3]

Then

# break

# continue

# exit

Fi

Echo $i

Done

Echo OK

Results of the output

Result of break

1

2

Ok

Results of continue

1

2

4

Ok

Result of exit

1

2

This can explain

Break N/A indicates the number of layers that jump out of the loop, and if n is omitted to jump out of the loop

Continue n-n means to return to the nth level to continue the loop, if omitting n means jumping out of the loop, ignoring the remainder of the loop, and entering the next loop of the loop

Exit N: Exit the current shell program and return to N,n can also omit

Return: returned value of function

Example: Temporarily configure multiple IP addresses for the server and can revoke all IP configurations at any time

IP address: 10.0.0.1-10.10.0.0.16, where 10.0.0.10 cannot be configured

#ifconfig eth0:1 10.10.0.1 netmask 255.255.0.0 up

A simple implementation

For ((i=1;i<=16;i++))

Do

If [$i-eq 10]

Then

Continue

Fi

Ifconfig eth0: $i 10.0.0. $i netmask 255.255.0.0 down

Done

Or

Case "$" in

Start

For ((i=1;i<=16;i++))

Do

If [$i-eq 10]

Then

Continue

Fi

Ifconfig eth0: $i 10.0.0. $i netmask 255.255.0.0 "$"

Done

;;

Stop

For ((i=1;i<=16;i++))

Do

If [$i-eq 10]

Then

Continue

Fi

Ifconfig eth0: $i 10.0.0. $i netmask 255.255.0.0 "$"

Done

;;

*)

echo "usage:$0 [Start|stop]"

Esac

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