【Shell】Shell程式設計之for迴圈命令
阿新 • • 發佈：2019-01-08
bash shell提供了for命令，用於建立通過一系列值重複的迴圈，for命令的格式為：
for var in list
do
commands
done[[email protected] bash_stu]# cat test1.sh
#!/bin/bash
#basic for command
for var in China Japan USA UK Canada
do
echo The next contry is $var
done
[ [[email protected] bash_stu]# cat test1.sh
#!/bin/bash
#basic for command
for var in China Japan USA UK Canada
do
echo The next contry is $var
done
echo The last value for contry is $var
var=Alen
echo The last value is $var
[ [[email protected] bash_stu]# cat test2.sh
#!/bin/bash
#basic for command
for var in Welcome to New York It's my baby's dog -- New York為一個整體
do
echo The word is $var
done
[[email protected] bash_stu]# . test2.sh
The word is Welcome
The word is to
The word is New
The word is York
The word is Its my babys
The word is dog
[[email protected] bash_stu]# - 使用轉義字元（\）；
- 使用雙引號定義使用單引號的值。
[[email protected] bash_stu]# cat test2.sh
#!/bin/bash
#basic for command
for var in Welcome to "New York" It\'s my "baby's" dog --分別使用雙引號和轉義解決
do
echo The word is $var
done
[[email protected] bash_stu]# . test2.sh
The word is Welcome
The word is to
The word is New York
The word is It's
The word is my
The word is baby's
The word is dog
[[email protected] bash_stu]# [[email protected] bash_stu]# cat test2.sh
#!/bin/bash
#basic for command
list="Welcome to learn shell"
list=$list" Alen" --將一個變數增加到一個已存在的變數中
for var in $list
do
echo The word is $var
done
[[email protected] bash_stu]# . test2.sh
The word is Welcome
The word is to
The word is learn
The word is shell
The word is Alen
[[email protected] bash_stu]# [[email protected] bash_stu]# cat test2.sh
#!/bin/bash
#basic for command
f="country.txt"
for var in `cat $f`
do
echo The word is $var
done
[[email protected] bash_stu]# cat country.txt
China
Japan
USA
UK
[[email protected] bash_stu]# . test2.sh
The word is China
The word is Japan
The word is USA
The word is UK
[[email protected] bash_stu]# [[email protected] bash_stu]# cat test2.sh
#!/bin/bash
#basic for command
f="country.txt"
IFS=$'\n' --重新定義欄位分隔符，忽略空格和製表符
for var in `cat $f`
do
echo The word is $var
done
[[email protected] bash_stu]# . test2.sh
The word is China Beijing
The word is Japan
The word is USA New York
The word is UK
[[email protected] bash_stu]# [[email protected] bash_stu]# cat test2.sh
#!/bin/bash
#basic for command
for var in /root/bash_stu/*
do
if [ -d $var ]
then
echo "$var is a directory"
elif [ -f $var ]
then
echo "$var is a file"
fi
done
[[email protected] bash_stu]# . test2.sh
/root/bash_stu/country.txt is a file
/root/bash_stu/test1.sh is a file
/root/bash_stu/test2.sh is a file
/root/bash_stu/tt is a directory
[[email protected] bash_stu]# [[email protected] bash_stu]# cat test2.sh
#!/bin/bash
v=1;
for((i=1;i<5;i++))
do
echo $v + $i = $(($v+$i))
done
[[email protected] bash_stu]# . test2.sh
1 + 1 = 2
1 + 2 = 3
1 + 3 = 4
1 + 4 = 5
[[email protected] bash_stu]# [[email protected] bash_stu]# cat test2.sh
#!/bin/bash
for((i=1,j=5;i<5;i++,j--))
do
echo $i + $j = $(($i+$j))
done
[[email protected] bash_stu]# . test2.sh
1 + 5 = 6
2 + 4 = 6
3 + 3 = 6
4 + 2 = 6
[[email protected] bash_stu]# [[email protected] bash_stu]# cat test2.sh
#!/bin/bash
for ((i=1;i<=100;i++))
do
if [ $(($i%3)) -eq 0 ]
then
echo "$i"
fi
done
[[email protected] bash_stu]# . test2.sh
3
6
9
12
15
18
21
24
27
--------------------省略---------------------[[email protected] bash_stu]# cat test2.sh
#!/bin/bash
for((i=1;i<=9;i++))
do
for((j=1;j<=i;j++))
do
echo -n "$i*$j=$(($i*$j)) "
done
echo ""
done
[[email protected] bash_stu]# . test2.sh
1*1=1
2*1=2 2*2=4
3*1=3 3*2=6 3*3=9
4*1=4 4*2=8 4*3=12 4*4=16
5*1=5 5*2=10 5*3=15 5*4=20 5*5=25
6*1=6 6*2=12 6*3=18 6*4=24 6*5=30 6*6=36
7*1=7 7*2=14 7*3=21 7*4=28 7*5=35 7*6=42 7*7=49
8*1=8 8*2=16 8*3=24 8*4=32 8*5=40 8*6=48 8*7=56 8*8=64
9*1=9 9*2=18 9*3=27 9*4=36 9*5=45 9*6=54 9*7=63 9*8=72 9*9=81
[[email protected] bash_stu]# [[email protected] bash_stu]# cat test2.sh
#!/bin/bash
for((i=1;i<=9;i++))
do
for((j=1;j<=i;j++))
do
echo -n "$i*$j=$(($i*$j)) "
done
echo ""
done > mu.txt
[[email protected] bash_stu]# . test2.sh
[[email protected] bash_stu]# cat mu.txt
1*1=1
2*1=2 2*2=4
3*1=3 3*2=6 3*3=9
4*1=4 4*2=8 4*3=12 4*4=16
5*1=5 5*2=10 5*3=15 5*4=20 5*5=25
6*1=6 6*2=12 6*3=18 6*4=24 6*5=30 6*6=36
7*1=7 7*2=14 7*3=21 7*4=28 7*5=35 7*6=42 7*7=49
8*1=8 8*2=16 8*3=24 8*4=32 8*5=40 8*6=48 8*7=56 8*8=64
9*1=9 9*2=18 9*3=27 9*4=36 9*5=45 9*6=54 9*7=63 9*8=72 9*9=81
[[email protected] bash_stu]#