shell命令行参数

-bash-4.2$ cat test1.sh

#!/bin/sh

echo "$0  "

echo "$1  "

echo "$2  "

-bash-4.2$ ./test1.sh a b c

./test1.sh  

a  

b  

-bash-4.2$ 

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显示全部命令行參数

-bash-4.2$ cat test1.sh

#!/bin/sh

until [ -z "$1" ]

do

   echo "$1  "

   shift

done

-bash-4.2$ ./test1.sh a b c d e f

a  

b  

c  

d  

e  

f 

-bash-4.2$ cat test1.sh

#!/bin/sh

index=1

for myarg in $*

do

   echo "NO#$index=$myarg"

   let "index+=1"

done

-bash-4.2$ ./test1.sh a b c d e f

NO#1=a

NO#2=b

NO#3=c

NO#4=d

NO#5=e

NO#6=f

-bash-4.2$ 

条件表达式

-bash-4.2$ cat test1.sh

#!/bin/sh

a=1

b=2

if [ $a -gt $b ]

then

   echo "GT"

else

   echo "LT"

fi

-bash-4.2$ ./test1.sh

LT

-bash-4.2$ 

-bash-4.2$ cat test1.sh

#!/bin/sh

a=2

b=2

if [ $a -gt $b ]

then

   echo "GT"

elif [ $a -eq $b ]

then

   echo "eq"

else

   echo "LT"

fi

-bash-4.2$ ./test1.sh

eq

-bash-4.2$ 

-bash-4.2$ cat test1.sh

#!/bin/sh

echo "====================="

echo "1.a"

echo "2.b"

echo "3.c"

read  mychoice

case $mychoice in

     1 ) echo "a";;

     2 ) echo "b";;

     3 ) echo "c";;

esac

exit 0

-bash-4.2$ ./test1.sh

=====================

1.a

2.b

3.c

2

b

-bash-4.2$ 

循环

-bash-4.2$ cat test1.sh

#!/bin/sh

for filename in `ls`

do

    echo $filename

done

-bash-4.2$ ./test1.sh

1

abc

abd

error.log

hadoop-2.4.1

hadoop-2.4.1-src.tar.gz

hadoop-2.4.1.tar.gz

hello

mydoclist

显示全部偶数

:和true都表示为真的意思

-bash-4.2$ cat test1.sh

#!/bin/sh

a=0

while :

do

  let "a=$a + 1"

   if[ $a -gt 20 ]

  then

     break

   fi

   if[ $(($a%2)) -eq  1 ]

  then

     continue

   fi

  echo $a

done  

-bash-4.2$ ./test1.sh

2

4

6

8

10

12

14

16

18

20

-bash-4.2$