Home | 简体中文 | 繁体中文 | 杂文 | 打赏(Donations) | ITEYE 博客 | OSChina 博客 | Facebook | Linkedin | 知乎专栏 | Search | Email

1.5. Loops for, while and until

1.5.1. for

		
#!/bin/bash
for i in 1 2 3 4 5
do
   echo "Welcome $i times"
done

for i in $( ls ); do
    echo item: $i
done

for i in `seq 1 10`;
do
    echo $i
done

for i in {1..5}
do
   echo "Welcome $i times"
done

for (( c=1; c<=5; c++ ))
do
	echo "Welcome $c times..."
done

for ((i=1; $i<=9;i++)); do echo $i; done
		
		
for i in {0..10..2}
do
    echo "Welcome $i times"
done

for i in $(seq 1 2 20)
do
   echo "Welcome $i times"
done
		

单行实例

for ip in {1..10};do echo $ip; done

for i in `seq 1 10`;do echo $i;done

for ip in {81..92}; do ssh root@172.16.3.$ip date; done

for n in  {23..32} {49,50} {81..92}; do mkdir /tmp/$n; echo $n; done
		
		
for keyword in bash cmd ls
do
	echo $keyword
done 

string="aaa bbb ccc ddd" && for word in $string; do echo "$word"; done

	
files=( "/etc/passwd" "/etc/group" "/etc/hosts" )
for file in "${files[@]}"
do
    echo $file
done
		
		

infinite loops

		
#!/bin/bash
for (( ; ; ))
do
   echo "infinite loops [ hit CTRL+C to stop]"
done


		
		

find file

#!/bin/bash
for file in /etc/*
do
	if [ "${file}" == "/etc/resolv.conf" ]
	then
		countNameservers=$(grep -c nameserver /etc/resolv.conf)
		echo "Total  ${countNameservers} nameservers defined in ${file}"
		break
	fi
done
		

backup file

#!/bin/bash
FILES="$@"
for f in $FILES
do
        # if .bak backup file exists, read next file
	if [ -f ${f}.bak ]
	then
		echo "Skiping $f file..."
		continue  # read next file and skip cp command
	fi
        # we are hear means no backup file exists, just use cp command to copy file
	/bin/cp $f $f.bak
done
		
for n in  {23..32} {49,50} {81..92}; do mkdir /tmp/$n; echo $n; done
		

1.5.2. while

		
#!/bin/bash
COUNTER=0
while [  $COUNTER -lt 10 ]; do
    echo The counter is $COUNTER
    let COUNTER=COUNTER+1
done
		
		
		
while read name age
do
	echo $name $age
done << EOF
neo 30
jam 31
john 29
EOF


while read name age
do
	[[ $age -gt 30 ]] && echo $name
done << EOF
neo 30
jam 31
john 29
EOF
		
		
		
$ cat mount.sh
#!/bin/sh
while read LINE
do

	s=`echo $LINE|awk '{print $1}'`
	d=`echo $LINE|awk '{print $2}'`

	umount -f $d
	mount -t nfs4 $s $d

done < mount.conf

$ cat mount.conf
172.16.0.1:/	/www/logs/1
172.16.0.2:/	/www/logs/2
172.16.0.3:/	/www/logs/3
172.16.0.4:/	/www/logs/4
172.16.0.5:/	/www/logs/5
		
		

读一行

		
while IFS='' read -r line || [[ -n "$line" ]]; do
	echo "Text read from file: $line"
done < "$1"
		
		
		

1.5.3. until

		
#!/bin/bash
COUNTER=20
until [  $COUNTER -lt 10 ]; do
    echo COUNTER $COUNTER
    let COUNTER-=1
done