数学思想方法-分布式计算-linux/unix技术基础(5)

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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http://blog.csdn.net/myhaspl/

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$