shell脚本入门

1.按日期建立文件
echo 'auto touch 3 files '
read -p "please enter your filename : " file

filename=${file:-"filename"}

date1=`date --date='2 days ago' +%Y%m%d`
date2=`date --date='1 days ago' +%Y%m%d`
date3=`date +%Y%m%d`
file1="$filename""$date1"
file2="$filename""$date2"
file3="$filename""$date3"

touch $file1
touch $file2
touch $file3

2.查看文件的权限
read -p 'enter a file name: ' file
test -z $file && echo 'you must input a filename'&&exit 0
test ! -e $file && echo 'the file not exist' && exit 0
test -f $file && filetype="regular file"
test -d $file && filetype="directory"
test -r $file && perm="readable"
test -w $file && perm="$perm writable"
test -x $file && perm="$perm excutable"

echo "the filename : $file is a $filetype"
echo "the permission of the file is : $perm"

3.if ... ; then elif else fi
if [ "$c" == "Y" ] || [ "$c" == "y" ]; then
echo "ok,continue"
exit 0
elif [ "$c" == "N" ] || [ "$c" == "n" ]; then
echo "interrupt"
exit 0
else
echo "I don't know your choice"
fi

4.use prameters of script
echo "The script name is : $0 "
[ -n "$1" ] && echo "the first param is : $1" || exit 0
[ -n "$2" ] && echo "the second param is : $2" || exit 0
[ -n "$3" ] && echo "the third param is : $3" || exit 0

5.case .. esac
case $1 in
"hello")
echo "Hello ,how are you ?"
;;
"")
echo "you must input parameters, ex > $0 someword"
;;
*)
echo "Use $0 {hello}"
;;
esac

6.检查网络服务
testing=`netstat -tuln | grep ":80 "`
if [ "$testing" != "" ]; then
echo "www is running "
fi

testing=`netstat -tuln | grep ":22 "`
if [ "$testing" != "" ]; then
echo "ssh is running"
fi

testing=`netstat -tuln | grep ":21 "`
if [ "$testing" != "" ]; then
echo "ftp is running"
fi

testing=`netstat -tuln | grep ":25 "`
if [ "$testing" != "" ]; then
echo "mail is running"
fi

7.计算时间
read -p "please input your demobilization date : " q
date_d=`echo $q|grep '[0-9]\{8\}'`
if [ "$date_d" == "" ]; then
echo "you input wrong format of date"
exit 0
fi

declare -i time=`date --date="$q" +%s`
declare -i now=`date +%s`
declare -i wait=$(($time-$now))
day=$(($wait/3600/24))
if [ "$day" -lt "0" ]; then
echo "your had been demobilization before " $((-1*$day)) " ago"
else
echo "you have $day days to leave"
fi

8.函数
function print(){
echo "YOur choice is $1"
}

echo 'this program will print your selection@!'

case $1 in
"one")
print $1
;;
"two")
print $1
;;
"three")
print $1
;;
*)
echo 'Usage (one|two|three)'
;;
esac

9.while循环
while [ "$y" != "yes" ] && [ "$y" != "YES" ]
do
read -p "Please input yes or YES to stop the program : " y
done

10.until
until [ "$y" == "yes" ] || [ "$y" == "YES" ]
do
read -p "Please input yes or YES to stop the program : " y
done

11.for循环
s=0
for (( i=1; i<=100; i++ ))
do
s=$(($s+$i))
done
echo "the result of 1+2+3+...+100 is ===> $s"

another for：
for animal in dog cat elephant
do
echo "there are $animal s.."
done

12.路径检测
read -p "please input a dir : " dir
if [ "$dir" == "" ] || [ ! -d "$dir" ]; then
echo "the $dir not exists in your system"
exit 1
fi

list=`ls $dir`

for file in $list
do
perm=""
test -r "$dir/$file" && perm="$perm readable"
test -w "$dir/$file" && perm="$perm writable"
test -x "$dir/$file" && perm="$perm executable"
echo "the permissions of the file $dir/$file is : $perm"
done

13.文件检测
name="/tmp/logical"
if [ ! -e "$name" ]; then
echo 'not exist'
touch "$name"
elif [ -d "$name" ]; then
echo 'dir'
rm -r "$name"
elif [ -f "$name" ]; then
echo 'file'
rm -r "$name"
touch "$name"
else
echo "It's neither a dir nor a file"
fi

14.文件分析
list=`cut -d ':' -f1 /etc/passwd`
i=0
for user in $list
do
i=$(($i+1))
echo "The $i account is $user"
done