轻度Linux服务器维护人员常用的Shell脚本命令

# 仅打包，不压缩
tar -cvf /usr/local/test.tar /usr/local/test
# 解包
tar –xvf test.tar

# 打包后，用bzip2压缩
tar -jcvf /usr/local/test.tar.bz2 /usr/local/test
# 解压bzip2包
tar -jxvf /usr/local/test.tar.bz2

# 打包后，用gzip压缩
tar -zcvf /usr/local/test.tar.gz /usr/local/test
# 解压gzip包
tar -zxvf /usr/local/test.tar.gz

# 列出所有服务
chkconfig --list
# 增加httpd服务
chkconfig --add httpd
# 删除httpd服务
chkconfig --del httpd

# 列出系统中所有安装java程序的路径，并选择默认程序
update-alternatives --config java

# ./testing -a -b test1 -d
# Found the -a option
# Found the -b option. with parameter value test1
# -d is not an option
# extracting command line options and values

while [ -n "$1" ]
do
    case "$1" in
    -a) echo "Found the -a option";;
    -b) param="$2"
        echo "Found the -b option, with parameter value $param"
        shirt 2;;
    -c) echo "Found the -c option";;
    --) shift
        break;
    *) echo "$1 is not an option";;
    esac
    shift
done

count=1
for param in "$@"
do
    echo "Parameter #$count: $param"
    count=$[ $count + 1 ]
done

# 文件或路径不存在的返回码是2
ls -al badfile 2> testfile
cat testfile
# ls: cannot access badfile: No such file or directory

ls -al test test2 test3 badtest 2> testfile 1> testfile2
cat testfile
# ls: cannot access test: No such file or directory
# ls: cannot access badtest: No such file or directory
cat testfile2
# -rw-rw-r--.   1 rich rich 158 2010-10-16 11:32 test2
# -rw-rw-r--.   1 rich rich   0 2010-10-16 11:33 test3

date | tee testfile
# Sun Oct 17 18:56:21 EDT 2010

# smenu1
PS3="Enter option: "
select option in "Display disk space" "Display logged on users" "Display memory usage" "Exit program"
do
    case $option in
    "Exit program")
        break ;;
    "Display disk space")
        df -k ;;
    "Display logged on users")
        who ;;
    "Display memory usage")
        cat /proc/meminfo ;;
    *)
        clear
        echo "Sorry, wrong selection" ;;
    esac
done
clear
# ./smenu1
# 1) Display disk space       3) Display memory usage
# 2) Display logged on users  4) Exit program
# Enter option: 

# 2个变量相除，结果为4位小数
var1=100
var2=45
var3=`echo "scale=4; $var1 / $var2" | bc`
echo The answer for this is $var3
# The answer for this is 2.2222

# 数组遍历
array_name=(value0 value1 value2 value3 value4)
for value in ${array_name[@]}; do
    echo value
done

## 常用ss命令
ss -l #显示本地打开的所有端口
ss -pl #显示每个进程具体打开的socket
ss -t -a #显示所有tcp socket
ss -u -a #显示所有的UDP Socekt
ss -o state established '( dport = :smtp or sport = :smtp )' #显示所有已建立的SMTP连接
ss -o state established '( dport = :http or sport = :http )' #显示所有已建立的HTTP连接
ss -x src /tmp/.X11-unix/* #找出所有连接X服务器的进程
ss -s #列出当前socket详细信息

if command1
then
    commands
elif command2
then
    more commands
else
    more commands
fi
# or
if command1; then
    commands
elif command2; then
    more commands
else
    more commands
fi

case variable in
pattern1 | pattern2)
    commands1;;
pattern3)
    commands2;;
*)
    default commands;;
esac

for var in list
do
    commands
done
# or
for var in list; do
    commands
done
# or
for (( variable assignment ; condition ; iteration process )); do
    commands
done

while test command
do
    commands
done
# or
while test command; do
    commands
done
# or 读取文件
while read line; do
    echo "$line"
done

until test command
do
    commands
done
# or
until test command; do
    commands
done

function name {
    commands
}
# or
name() {
    commands
}

function db1 {
    read -p "Enter a value: " value
    echo $[ $value * 2 ]
}
result=`db1`
echo "The new value is $result"