Circular statements and judgment statement examples in shell

#!/bin/bash

for file in $(ls /tmp/test/mytest |grep sh)   //For in format is the basic format of shell for, root js for in similar
do
 echo $file
done

for ((i=0;i<10;i++))            //Note that it is double brackets, and it is easy to make mistakes due to the influence of other languages.
do
 echo -n $i
done

echo \    //Output line break

for i in 0 1 2 3 4 5 6 7 8 9
do
 echo -n $i
done

echo \

for i in "0 1 2 3 4 5 6 7 8 9"     //There is a difference above this root. This loop only loops once, and it is just a variable in the double quotes
do
 echo -n $i
done

exit 0

#!/bin/bash
i=0
while ((i<10))
do
 echo $i
 ((i += 1))
done

i=0
while [ $i -lt 10 ]  //Note the spaces on the two sides inside the brackets
do
 echo $i
let "i+=1"   //Add 1
done
exit 0

#!/bin/bash

END_CONDITION=end
until [ "$var1" = "$END_CONDITION" ]  //The variables set by the read variables are equal when the variables are set, otherwise the loop will be looped forever
do
 echo "Input variable #1 "
 echo "($END_CONDITION to exit)"
 read var1
 echo "variable #1 = $var1"
 echo
done  
exit 0

#!/bin/bash

echo "Input a number #1 "
read num
echo "variable #1 = $num"

if [ $num -lt 60 ]    //Note the - in front of lt, it is easy to forget
then
 echo "you are not pass"
elif [ $num -lt 70 ] && [ $num -ge 60 ]  //Judgement of multiple conditions
then
 echo "pass"
elif [[ $num -lt 85 && $num -ge 70 ]] //If put together, be careful to be bracketed in both squares and do not write it as [ $num -lt 85 && $num -ge 70 ]
then
 echo "good"
elif (( $num <= 100 )) && (( $num >= 85 )) //For people with language foundation, this writing makes people feel very comfortable. Don’t forget that it is double brackets
then
 echo "very good"
else
 echo "num is wrong"
fi

exit 0

#!/bin/sh
case $1 in
 start)
 echo "start ok"
;;      //Be careful, be careful of the double semicolon
 stop)
 echo "stop  ok"
 ;;
 restart)
 echo "restart ok"
 ;;
 *)
 echo "no param"
 ;;
esac     //Be careful to close the tag
exit 0

[root@krlcgcms01 forif]# sh stop
stop  ok