2018-05-31 Linux Learning

20.10 for Loop

Syntax: for variable name in condition; Do ...; Done

Case 1
#!/bin/bash
Sum=0
For I inseq 1 100
Do
echo "$sum + $i"
sum=$[$sum + $i]
Echo $sum
Done
Echo $sum

Case 2
File list loop
#!/bin/bash
cd/etc/
For a in ls/etc/
Do
If [-D $a]
Then
LS $a
Fi
Done

Operation Process

Case 1

[Email protected] shell]# vim for1.sh
#!/bin/bash
Sum=0
For I inseq 1 100
Do
sum=$[$sum + $i]
Done
Echo $sum

[[email protected] shell]# sh for1.sh 5050

Case 2

[Email protected] shell]# vim for2.sh
#!/bin/bash
cd/etc/
For a in ls/etc/
Do
[-D $a] && ls $a
Done

20.11 While loop

syntax while condition; Do ...; Done
Case 1
#!/bin/bash
While:
Do
load= w|head-1|awk-f ' Load average: ' {print $} ' |cut-d. -f1
If [$load-GT 10]
Then
Top|mail-s "Load is High: $load" [email protected]
Fi
Sleep 30
Done

Case 2
#!/bin/bash
While:
Do
Read-p "Please input a number:" N
If [-Z "$n"]
Then
echo "You need input sth."
Continue
Fi
n1=echo $n|sed ‘s/[0-9]//g‘
If [-N "$n 1"]
Then
echo "You just only input numbers."
Continue
Fi
Break
Done
Echo $n

Operation Process

Case 1

[[email protected] shell]# uptime|awk -F ‘load average:‘ ‘{print $2}‘ 0.00, 0.01, 0.05[[email protected] shell]# uptime|awk -F ‘load average:‘ ‘{print $2}‘|cut -d . -f1 0[[email protected] shell]# uptime|awk -F ‘load average:‘ ‘{print $2}‘|cut -d . -f1|sed ‘s/ //‘0

[Email protected] shell]# vim while1.sh
#!/bin/bash
While True
Do
load= w|head-1|awk-f ' Load average: ' {print $} ' |cut-d. -f1
If [$load-GT 10]
Then
/usr/local/sbin/mail.py [email protected] "load High" "$load"
Fi
Sleep 30
Done

Case 2

[Email protected] shell]# vim while2.sh
#!/bin/bash
While:
Do
Read-p "Please input a number:" N
If [-Z "$n"]
Then
echo "You need input sth."
Continue
Fi
n1=echo $n|sed ‘s/[0-9]//g‘
If [-N "$n 1"]
Then
echo "You just only input numbers."
Continue
Fi
Break
Done
Echo $n

[[email protected] shell]# sh while2.sh Please input a number: sssyou just only input numbers.Please input a number: ....you just only input numbers.Please input a number: 00

20.13 break jump out of the loop

#!/bin/bash
For I inseq 1 5
Do
? ? Echo $i
? ? if [$i = = 3]
? ? Then
? ?? ??? Break
? ? Fi
? ? Echo $i
Done
Echo AAAAAAA

Operation Process

[Email protected] shell]# vim break.sh

#!/bin/bash
For I inseq 1 5
Do
Echo $i
If [$i-eq 3]
Then
Break
Fi
Echo $i
Done
Echo aaaaaa

[[email protected] shell]# sh break.sh 11223aaaaaa

20.14 continue ends this cycle

Ignore the code under continue and proceed to the next loop directly
#!/bin/bash
For I inseq 1 5
Do
? ? Echo $i
? ? if [$i = = 3]
? ? Then
? ?? ??? Continue
? ? Fi
? ? Echo $i
Done
Echo $i

Operation Process

[Email protected] shell]# vim continue.sh

#!/bin/bash
For I inseq 1 5
Do
Echo $i
If [$i-eq 3]
Then
Continue
Fi
Echo $i
Done
Echo aaaaaa

[[email protected] shell]# sh continue.sh 112234455aaaaaa

20.15 exit exits the entire script

[Email protected] shell]# vim exit.sh

#!/bin/bash
For I inseq 1 5
Do
Echo $i
If [$i-eq 3]
Then
Exit
Fi
Echo $i
Done
Echo aaaaaa

[[email protected] shell]# sh exit.sh 11223

2018-05-31 Linux Learning