Recording learning shell (. 6) while nesting and until and while

while the five kinds of conditions

1. mathematical comparison

1 read -p "Num :" num1
2 while [ $num1 -gt 0 ]
3   do
4       echo 'greater'
5       sleep 1
6 
7 done

2. string comparison

1 read -p "enter the password:" pw
2 while [ $pw != password ]
3   do
4       read -p "enter the password:" pw
5 
6 done
7 echo 'welcome'

3. detect whether a file exists

1 while [ ! -e /tmp/testfolder  ]
2   do
3       echo '/tmp/testfolder not exist'
4       sleep 1
5 done

4. Analyzing the plurality of conditions

 1 read -p "money:" money
 2 read -p "car:" car
 3 read -p "house:" house
 4 
 5 while [ $money -lt 100000 ] || [ $car -lt 1 ] || [ $house -lt 1 ]
 6   do
 7         echo 'no way!'
 8         read -p "money:" money
 9         read -p "car:" car
10         read -p "house:" house
11 done
12 echo 'Ok!'

 5. Analyzing Assignment

1 read -p "char:" ch
2 
3 while [ $ch != 'q' ]
4   do
5         echo "char is : $ch"
6         read -p "char:" ch
7 done
8 echo 'you just press q'

 6. The wording is similar for

1 i=1
2 while [ $i -lt 10 ]
3   do
4       echo $i
5       i=$((i+1))
6 done

7.while also continue using the break when the need to pay attention to the order of accumulation

. 1 I = . 1 
2  the while [$ I -LT- 10 ]
 . 3    do 
. 4        echo $ I
 . 5        I = $ ((I + . 1 ))
 . 6        IF [$ I -eq . 5 ]; the then
 . 7           Continue 
. 8        Fi
 . 9        #i = $ ( (I + . 1 )) when the first accumulation continue, when the accumulated BREAK
 10 DONE

 8. The multiplication table

. 1 n-= . 1 
2  the while [-LT-n-$ 10 ]
 . 3  do 
. 4        for ((m = . 1 ; m <= $ n; m ++ )) # where m <= $ n written if m <pattern 10 will output very different
 . 5           do 
. 6           echo -n -e " $ $ n-MX = $ ((n-m *)) \ T " 
. 7        DONE
 . 8        echo
 . 9        n-= $ ((n-+ . 1 ))
 10 DONE

 If the above for double while that is replaced while nesting

 1 n=1
 2 while [ $n -lt 10 ]
 3 do
 4       #for (( m=1;m<=$n;m++ ))
 5       # do
 6       m=1
 7       while [ $m -lt $n ];do
 8 
 9          echo -n -e "$m x $n = $((n*m))\t"
10 
11       m=$(($m+1))
12       done
13       echo
14       n=$((n+1))
15 done

 9. Read the contents of the passwd

1 while read i;do
2   echo $i
3 done < /etc/passwd

 

10. Read the contents of the passwd fifth column shows only the first row in the third column

1 IFS=$":"
2 while read f1 f2 f3 f4 f5 f6 f7;do
3     echo "$f1 $f3 $f5"
4 
5 done < /etc/passwd

 11.until 

　The difference is that until and while the condition is false until it is executed

   Print 10-20

1 i=10
2 until [ $i -gt 20 ];do
3   echo $i
4   i=$((i+1))
5 done