shell脚本

shell脚本的三种调试方法：

-n 读一遍脚本中的命令但不执行，用来检查脚本中的语法错误
-v 一边执行脚本，一边将执行过的脚本命令打印到标准输出端
-x 提供跟踪执行信息，将执行的每一条命令和结果一次打印出来，这应该就像C语言的gdb一样有用吧，有助于检查错误
使用这些选项有三种方法
1.在命令行提供参数：$sh -x script.sh
2.脚本开头提供参数：#!/bin/sh -x
3.在脚本中用set命令启用or禁用参数：其中set -x表启用，set +x表禁用

另：在写脚本的时候，需特别注意添加空格或换行或分号
eg   text命令：  $[ 5 -lt 10 ]左方括号后须有空格，右方括号前也须有空格
        shell脚本中函数定义： foo() {后须有空格或换行

        shell脚本中，若同一行内写有两条命令须加分号

1 交互式获取内容设置到shell变量

#!/bin/bash

read -p "Please input your first name: " firstname #提示用户输入
read -p "Please input your last name: " lastname #提示用户输入
echo -e "
Your full name is: $firstname $lastname, congratulation!"

输出

asn@asn-vm:~/Desktop/scripts$ ./sh02.sh
Please input your first name: asn
Please input your last name: judy

Your full name is: asn judy, congratulation!

2 循环

1) 打印系统中所有用户的信息

#!/bin/bash
# Program
# Use id, finger command to check system account's information.

users=$(cut -d ':' -f1 /etc/passwd)    #获取帐号名称
for username in $users
do
    id $username
    finger $username
done

输出：

asn@asn-vm:~/Desktop/scripts$ ./shell-user.sh

uid=0(root) gid=0(root) groups=0(root)
Login: root                       Name: root
Directory: /root                        Shell: /bin/bash
Never logged in.
No mail.
No Plan.

uid=1(daemon) gid=1(daemon) groups=1(daemon)
Login: daemon                     Name: daemon
Directory: /usr/sbin                    Shell: /usr/sbin/nologin
Never logged in.
No mail.
No Plan.


uid=1000(asn) gid=1000(asn) groups=1000(asn),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),108(lpadmin),124(sambashare),125(docker)
Login: asn                        Name: asnjudy@163.com
Directory: /home/asn                    Shell: /bin/bash
On since Fri Jul 10 19:25 (CST) on :0 from :0 (messages off)
On since Sat Jul 11 01:16 (CST) on pts/1 from :0
    3 seconds idle
Last login Fri Jul 10 21:15 (CST) on pts/25 from 192.168.204.1
No mail.
No Plan.


uid=116(sshd) gid=65534(nogroup) groups=65534(nogroup)
Login: sshd                       Name: 
Directory: /var/run/sshd                Shell: /usr/sbin/nologin
Never logged in.
No mail.
No Plan.

2）输入一个目录，查看该目录内文件的权限

#!/bin/bash

read -p "Please input a directory:" dir

if [ "$dir" == "" -o ! -d "$dir" ]; then
    echo "The $dir is NOT a existing  directory in your system."
    exit 1
fi

#开始测试文件
filelist=$(ls $dir)
for filename in $filelist
do
    perm=""
    test -r "$dir/$filename" && perm="$perm readable"
    test -w "$dir/$filename" && perm="$perm writable"
    test -x "$dir/$filename" && perm="$perm executable"
    echo "The file $dir/$filename's permission is $perm"
done

输出：

asn@asn-vm:~/Desktop/scripts$ chmod +x shell-dir.sh 
asn@asn-vm:~/Desktop/scripts$ ./shell-dir.sh
Please input a directory:/home/asn/Desktop
The file /home/asn/Desktop/alauda-CLI's permission is  readable writable executable
The file /home/asn/Desktop/c_test's permission is  readable writable executable
The file /home/asn/Desktop/scripts's permission is  readable writable executable
The file /home/asn/Desktop/shell-if.sh~'s permission is  readable writable executable
The file /home/asn/Desktop/test.cpp's permission is  readable writable

3 函数

#!/bin/bash

printit() {
    echo "Your choice is $1"
}

echo "This program will print your selection!"
case $1 in
    "one")
        printit hello-1
        ;;
    "two")
        printit hell0-2
        ;;
    "three")
        printit hello-3
        ;;
    *)
        echo "Usage $0 {one|two|three}"
        ;;
esac

输出：

asn@asn-vm:~/Desktop/scripts$ sh shell-fun.sh one
This program will print your selection!
Your choice is hello-1

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC/+pXV5xK8TEbHpxGrjIYsKdmEEeyaSjrPPNYSKmbysxNTnWxu4pCxkW+bPMl7S0aPQcx/sQkonQ0HohIVCUG0SUXdV2JsOWmYQT29/Pi97V+rKmtFAl8O+JC7T2NBbB5I4PvDMDjMGt9bN6Jt7HcYN1IH2qXBwyi1l+5iy4bY8H1kslWbNcXalooSSYEgO1YbPilvJuoAG5WSB27v77GwEsWs4uNeSjmbTf7qe5PfhH0+8YtJd6gNMYWzeWJLWRdYfUP4YwhIT5Um2cyqhggtbWX9aghRXGd8wJnfudCGRz765Itob24+L8t190T3yAgjFUnoAm2Vd5kgHMUq5HYd asn@asn-vm