shell循环示例,shell示例 for循环将放弃当

shell循环示例,shell示例 for循环将放弃当

for循环示例

for循环语法：

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for VARIABLE in 1 2 3 4 5 .. N

2

do

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command1

4

command2

5

commandN

6

done

01

#!/bin/bash

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03

foriin1 2 3 4 5

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05

do

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echo"Welcome $i times"

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09

done

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bash version 3.0+版本

#!/bin/bash

for i in {1..5}

do

echo "Welcome $i times"

done

bash version 4版本

#!/bin/bash

echo "Bash version ${BASH_VERSION}..."

for i in {0..10..2}

do

echo "Welcome $i times"

done

含有“seq”命令的语法示例

#!/bin/bash

for i in $(seq 1 2 20)

do

echo "Welcome $i times"

done

for循环的三个表达式

语法如下：

for (( EXP1; EXP2; EXP3 ))

do

command1

command2

command3

done

示例如下：

#!/bin/bash

for(( c=1; c<=5; c++ ))

do

echo"Welcome $c times..."

done

效果：

Welcome 1 times

Welcome 2 times

Welcome 3 times

Welcome 4 times

Welcome 5 times

for的无限循环

#!/bin/bash

for (( ; ; ))

do

echo "infinite loops [ hit CTRL+C to stop]"

done

break条件语句

for I in 1 2 3 4 5

do

statements1 #Executed for all values of ''I'', up to a disaster-condition if any.

statements2

if (disaster-condition)

then

break #Abandon the loop.

fi

statements3 #While good and, no disaster-condition.

done

下面的shell脚本将通过在/ etc目录中存储的所有文件。 for循环将放弃当/ etc / resolv.conf的文件中找到。

#!/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

continue条件语句

for I in 1 2 3 4 5

do

statements1 #Executed for all values of ''I'', up to a disaster-condition if any.

statements2

if (condition)

then

continue #Go to next iteration of I in the loop and skip statements3

fi

statements3

done

利用这个脚本在命令行中指定的所有文件名的备份。如果。bak文件存在，它会跳过cp命令。

#!/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