!/bin/bash

Author: zhangdongling

Copyright(C)

Script follows here:

echo "What is your name?"
read PERSON
echo "Hello ,$PERSON"


variableName="zhangdl"
name=dong
echo "variableName,$variableName"
echo "name,$name"


echo "1."$0 #当前脚本的文件名
echo "2."$1 #传递给脚本或函数的参数
echo "3."$# #传递给脚本或函数的参数个数。
echo "4."$* #传递给脚本或函数的所有参数。
echo "5."$@ #传递给脚本或函数的所有参数。被双引号(" ")包含时,与 $* 稍有不同,下面将会讲到。
echo "6."$? #上个命令的退出状态,或函数的返回值。大部分命令执行成功会返回0,失败返回1
echo "7."$$ #当前 Shell 进程 ID。
echo "8."$@""
echo "9."$*""
echo -e "pid is $$ n"
echo "pid is $$ n"


DATE=date
echo -e "DATE is $DATE n"
USERS=who | wc -l
echo -e "Logged in user are $USERS n"
UP=date;uptime
echo -e "Uptime is $UP n"


val=expr 2 + 2
echo "Total value:$val"


a=10
b=20
val=expr $a + $b
echo "a + b :$val"

val=expr $a - $b
echo "a - b :$val"

val=expr $a \* $b
echo "a * b :$val"

val=expr $a / $b
echo "a / b :$val"

val=expr $a % $b
echo "a % b :$val"

if [ $a == $b ]
then

echo " a is equal to b"

fi

if [ $a != $b ]
then

echo "a is not equal to b"

fi


a=10
b=20
if [ $a -eq $b ]
then

echo "$a -eq $b : a is equal to b"

else

echo "$a -eq $b : a is not equal to b"

fi

if [ $a -ne $b ]
then

echo "$a -ne $b : a is not equal to b"

else

echo "$a -ne $b : a is equal to b"

fi

if [ $a -gt $b ]
then

echo "$a -gt $b : a is less than b"

else

echo "$a -gt $b : a is not less than b"

fi

if [ $a -lt $b ]
then

echo "$a -lt $b :a  is less than b"

else

echo "$a -lt $b : a is not less than b"

fi

if [ $a -ge $b ]
then

echo "$a -ge $b : a is  greater or equal to b"

else

echo  "$a -ge $b : a  is not greater or equal to b "

fi

if [ $a -le $b ]
then

echo "$a -le  $b : a is less or equal to b"

else

echo "$a -le $b : a is not less or equal to b"

fi


file="/xxxx.sh"

if [ -r $file ]
then

echo "File has read access"

else

echo "File does not have read access"

fi

if [ -w $file ]
then

echo "File has write permission"

else

echo "File does not have write permission"

fi

if [ -x $file ]
then

echo "File has execute permission"

else

echo "File does not have execute permission"

fi

if [ -f $file ]
then

echo "File is an ordinary file"

else

echo "This is sepcial file"

fi

if [ -d $file ]
then

echo "File is a directory"

else

echo "This is not a direactory"

fi

if [ -s $file ]
then

echo "File size is zero"

else

echo "File size is not zero"

fi

if [ -e $file ]
then

echo "File exists"

else

echo "File does not exist"

fi

val=(a b c d e)
echo ${val[*]}
echo ${val[@]}
len=${#val[*]}
echo $len

for item in a b c d e
do

echo $item

done


function Hello(){

echo "Hello world"

}
Hello
echo $?


printf "Hello.shell n"
printf "%d,%sn" 1 zhangdl


str="abcd"
echo ${#str} # 字符串长度

str="alibaba is a great company"
echo ${str:1:4} # 提取字符串(数字表示字符串中字符对应下标)

string="alibaba is a great company"
val=expr length $string
echo $val