for循環
for 變量名 in 列表
do
命令 1
命令 2
done
當變量值在列表里，for循環即執行一次所有命令，使用變量名訪問列表中取值。命令可為任何有效的shell命令和語句。變量名為任何單詞。in列表用法是可選的，如果不用它， for循環使用命令行的位置參數。in列表可以包含替換、字符串和文件名，下面看一些例子。
- /home/l/g/tomotoboy/for >cat fortest
- #!/bin/sh
- #for_i
- for loop in 1 2 3 4 5 6
- do
- echo $loop
- done
-
- #forlist
- for loop in "orange red blue grey"
- do
- echo $loop
- done
-
- #forls
- for loop in `ls`
- do
- echo $loop
- done
-
-
- #forparam
- for params
- do
- echo "you supplied $params as command line option"
- echo $params
- done
-
- for params in "$@"
- do
- echo "you supplied $params as command line option"
- echo $params
- done
-
- #forcommand
- for loop
- do
- find `pwd` -name $loop -print
- done
-
-
- /home/l/g/tomotoboy/for >fortest fortest
- 1
- 2
- 3
- 4
- 5
- 6
- orange red blue grey
- fortest
- you supplied fortest as command line option
- fortest
- you supplied fortest as command line option
- fortest
/home/l/g/tomotoboy/for >cat fortest
#!/bin/sh
#for_i
for loop in 1 2 3 4 5 6
do
echo $loop
done
#forlist
for loop in "orange red blue grey"
do
echo $loop
done
#forls
for loop in `ls`
do
echo $loop
done
#forparam
for params
do
echo "you supplied $params as command line option"
echo $params
done
for params in "$@"
do
echo "you supplied $params as command line option"
echo $params
done
#forcommand
for loop
do
find `pwd` -name $loop -print
done
/home/l/g/tomotoboy/for >fortest fortest
1
2
3
4
5
6
orange red blue grey
fortest
you supplied fortest as command line option
fortest
you supplied fortest as command line option
fortest
使用for循環連接服務器
因為for循環可以處理列表中的取值，現設變量為網絡服務器名稱，并使用for循環連接每一服務器。
- #!/bin/sh
- #forping
- HOSTS="sina.com cqu.edu.cn baidu.com"
- for loop in $HOSTS
- do
- ping -c 2 $loop
- done
#!/bin/sh
#forping
HOSTS="sina.com cqu.edu.cn baidu.com"
for loop in $HOSTS
do
ping -c 2 $loop
done
多文件轉換
匹配所有以.sed結尾文件并將其轉換為大寫。這里使用了 l s和cat命令。l s用于查詢出相關文件，cat用于將之管道輸出至trr命令。目標文件擴展名為.UC，注意在for循環中使用l s命令時反引號的用法。
- #!/bin/sh
- #forstr
- for files in `ls *.sed`
- do
- cat $files |tr "[a-z]" "[A-Z]" >$files.UC
- done
-
- /home/l/g/tomotoboy >cat change.sed
- #!/bin/sed -f
- #change.sed
- /tomotoboy/ c\
- I love China,Ilove Wanzhi.
- /home/l/g/tomotoboy >ls *.UC
- append.sed.UC change.sed.UC
- /home/l/g/tomotoboy >cat change.sed.UC
- #!/BIN/SED -F
- #CHANGE.SED
- /TOMOTOBOY/ C\
- I LOVE CHINA,ILOVE WANZHI.
#!/bin/sh
#forstr
for files in `ls *.sed`
do
cat $files |tr "[a-z]" "[A-Z]" >$files.UC
done
/home/l/g/tomotoboy >cat change.sed
#!/bin/sed -f
#change.sed
/tomotoboy/ c\
I love China,Ilove Wanzhi.
/home/l/g/tomotoboy >ls *.UC
append.sed.UC change.sed.UC
/home/l/g/tomotoboy >cat change.sed.UC
#!/BIN/SED -F
#CHANGE.SED
/TOMOTOBOY/ C\
I LOVE CHINA,ILOVE WANZHI.
多sed刪除操作
下面的例子中，sed用于刪除所有空文件，并將輸出導至以 . HOLD.為擴展名的新文件，mv將這些文件移至初始文件中。
- #!/bin/sh
- #forsed
- for files in `ls *.sed`
- do
- sed -e "/^$/d" $files > $files.HOLD
- mv $files.HOLD $files
- done
#!/bin/sh
#forsed
for files in `ls *.sed`
do
sed -e "/^$/d" $files > $files.HOLD
mv $files.HOLD $files
done
循環計數
前面討論expr時指出，循環時如果要加入計數，使用此命令。下面使用 l s在for循環中列出文件及其數目。
- /home/l/g/tomotoboy >cat forcount
- #!/bin/sh
- #forcount
- count=0
- for files in *
- do
- count=`expr $count + 1`
- done
- echo "There are $count files in `pwd` we need to process"
/home/l/g/tomotoboy >cat forcount
#!/bin/sh
#forcount
count=0
for files in *
do
count=`expr $count + 1`
done
echo "There are $count files in `pwd` we need to process"