通常利用shell脚本完成服务器的检测工作，不涉及大量运算。
cat hello.sh 输出： #!/bin/bash #Program: # This program shows "hello world!" in your screen. #History: #2020/06/07 dj First release PATH=/bin:/sbin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH echo -e "hello world! a n" exit 0 #! 用来声明这个脚本使用的shell版本。
注释包括：
chmod a+x hello.sh 给3者都加上x的权限，这3者指的是文件所有者、文件所属组、其他人 cat showname.sh 输出： #!bin/bash #Program: # User inputs his first name and last name. Program shows his full name. #History: #2020/06/08 dj First relese PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH read -p "Please input your first name:" firstname read -p "Please input your last name:" lastname echo -e "nYour full name is: ${firstname} ${lastname}" cat create_3_filename.sh 输出： #!/bin/bash #Program: # Program create three files,which named by user's input and date command. #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH # 1.get file name from user echo -e "I will use 'touch' command to create 3 files." read -p "Please input your file name:" fileuser # 2. filename=${fileuser:-"filename"} # 3.get file name from date 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}${date3} # 4.create file touch "${file1}" touch "${file2}" touch "${file3}" 需要注意，date1=$(date --date='2 days ago' +%Y%m%d)的'2 days ago'与%Y%m%d之间务必要有一个空格！
[dj@study bin]$ sh create_3_filename.sh I will use 'touch' command to create 3 files. Please input your file name:djTest [dj@study bin]$ ll 总用量 12 -rw-rw-r--. 1 dj dj 674 6月 8 11:13 create_3_filename.sh -rw-rw-r--. 1 dj dj 0 6月 8 11:10 djTest -rw-rw-r--. 1 dj dj 0 6月 8 11:13 djTest20200606 这里可以看到新建的三个文件 -rw-rw-r--. 1 dj dj 0 6月 8 11:13 djTest20200607 这里可以看到新建的三个文件 -rw-rw-r--. 1 dj dj 0 6月 8 11:13 djTest20200608 这里可以看到新建的三个文件 -rwxrwxr-x. 1 dj dj 224 6月 7 20:14 hello.sh -rw-rw-r--. 1 dj dj 370 6月 8 10:57 showname.sh cat multiplying.sh 输出： #!/bin/bash # Program: # User inputs 2 integer numbers;program will cross these two numbers. # History: # 2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH echo -e "You SHOULD input 2 numbers,I will multiplying them!n" read -p "first number:" firstnumber read -p "second number:" secondnumber total=$((${firstnumber}*${secondnumber})) declare -i total1=${firstnumber}*${secondnumber} echo -e "nThe result of ${firstnumber} x ${secondnumber} is ==> ${total}" echo -e "nThe result of ${firstnumber} x ${secondnumber} is ==> ${total1}" 命令执行情况：
[dj@study bin]$ sh multiplying.sh You SHOULD input 2 numbers,I will multiplying them! first number:10 second number:6 The result of 10 x 6 is ==> 60 The result of 10 x 6 is ==> 60 说明这两种计算方式都是可以的：
total=$((${firstnumber}*${secondnumber})) declare -i total1=${firstnumber}*${secondnumber} 推荐：
var=$((运算内容)) 通过bc命令协助，计算含有小数点的数。
echo "123.123*2.3"|bc 输出： 283.182 cat cal_pi.sh 输出： #!/bin/bash #Program: # User input a scale number to calculate pi number. #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH echo -e "This program will calculate pi value.n" echo -e "You should input a float number to calculate pi value.n" read -p "The scale number (10~10000) ? " checking num=${checking:-"10"} echo -e "Starting calculate pi value. Be paient." time echo "scale=${num};4*a(1)" | bc -lq 其中，4*a(1)是bc提供的一个计算Pi的函数。运行情况：
[dj@study bin]$ sh cal_pi.sh This program will calculate pi value. You should input a float number to calculate pi value. The scale number (10~10000) ? 10 Starting calculate pi value. Be paient. 3.1415926532 real 0m0.004s user 0m0.002s sys 0m0.002s 利用直接执行的方式执行脚本，绝对路径、相对路径、${PATH}内、利用bash、利用sh，该脚本都会使用一个新的bash环境来执行脚本内的命令。是在子进程中执行的。 执行完毕后，所有数据被删除，父进程中读取不到。
利用source来执行脚本，在父进程中执行。 执行完毕后，数据都保留在父进程中。因此，为了让更新后的~/.bashrc生效，需要使用source ~/.bashrc，而不能用bash ~/.bashrc。
$? && ||
test用来检测系统上某些文件或是相关属性。
test -e /dj 检查这个文件或目录是否存在，执行后不会显示任何信息 搭配 $? 或 && 或 || 来展现结果：
test -e /dj && echo "exist" || echo "Not exist" 如果文件存在，继续执行&&右边的，否则，忽略&&直接执行||右边的 关于test的参数，书本第396页有个巨大的表格，可以参考。
常用如下：
| 测试的参数 | 意义 |
|---|---|
| -e | 看文件是否存在 |
| -f | 看文件是否存在且为文件 |
| -d | 看文件是否存在且为目录 |
cat file_perm.sh 输出： #!/bin/bash #Program: # User input a filename,program will check the following: # 1)exist? 2)file/directory? 3)file permissions #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/.bashrc export PATH # 1. 检查用户输入的内容是否为空 echo -e "Please input a filename,I will check the filename's type and permission.nn" read -p "Input a filename:" filename test -z ${filename} && echo "You MUST input a filename." && exit 0 # 2. 判断文件是否存在，不存在就退出 test ! -e ${filename} && echo "The filename '${filename}' DO NOT EXIST" && exit 0 # 3. 判断是文件还是目录；判断权限 test -f ${filename} && filetype="regular file" test -d ${filename} && filetype="directory" test -r ${filename} && perm="readable" test -w ${filename} && perm="${perm} writable" test -x ${filename} && perm="${perm} executable" # 4. 输出判断结果 echo "The filename: ${filename} is a ${filetype}" echo "And the permissions for you are:${perm}" 执行结果：
[dj@study bin]$ sh file_perm.sh Please input a filename,I will check the filename's type and permission. Input a filename:/home/dj The filename: /home/dj is a directory And the permissions for you are:readable writable executable 判断变量${HOME}是否为空： [ -z "${HOME}" ];echo $? 尤其注意，中括号[右侧有一个空格，中括号]左侧也有一个空格，否则报错 输出： 1 cat ans_yn.sh 输出： #!/bin/bash #Program: # This program shows the user's choice #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH read -p "Please input (Y/N):" yn [ "${yn}" == "Y" -o "${yn}" == "y" ] && echo "OK,continue" && exit 0 [ "${yn}" == "N" -o "${yn}" == "n" ] && echo "Oh,interrupt!" && exit 0 echo "I donot know what your choice is" && exit 0 执行结果：
[dj@study bin]$ sh ans_yn.sh Please input (Y/N): I donot know what your choice is [dj@study bin]$ sh ans_yn.sh Please input (Y/N):y OK,continue [dj@study bin]$ sh ans_yn.sh Please input (Y/N):N Oh,interrupt! /path/to/scriptname opt1 opt2 opt3 $0 $1 $2 $3 | 特殊变量 | 意义 |
|---|---|
| $# | 后接的参数个数，此处未3 |
| $@ | “$1” “$2” “$3”，每个变量是独立的 |
| $* | “$1c$2c$3”，c为分隔字符，默认为空格 |
cat show_paras.sh 输出： #!/bin/bash #Program: # Program shows the script name,parameters... #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH echo "The script name is ===> ${0}" echo "Total parameter number is ===> $#" [ "$#" -lt 2 ] && echo "The number of parameters is less than 2. Stop here." && exit 0 echo "Your whole parameters is ===> '$@'" echo "The 1st parameter ===> ${1}" echo "The 2nd parameter ===> ${2}" 执行情况：
sh show_paras.sh theone thetwo thethree The script name is ===> show_paras.sh Total parameter number is ===> 3 Your whole parameters is ===> 'theone thetwo thethree' The 1st parameter ===> theone The 2nd parameter ===> thetwo cat shift_paras.sh #!/bin/bash #Program: # Program shows the effect of shift function. #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH echo "Total parameter number is ==> $#" echo "Your whole parameter is ==> '$@'" shift echo "Total parameter number is ==> $#" echo "Your whole parameter is ==> '$@'" shift 3 echo "Total parameter number is ==> $#" echo "Your whole parameter is ==> '$@'" 执行情况：
[dj@study bin]$ sh shift_paras.sh theone thetwo thethree thefour thefive thesix Total parameter number is ==> 6 Your whole parameter is ==> 'theone thetwo thethree thefour thefive thesix' Total parameter number is ==> 5 Your whole parameter is ==> 'thetwo thethree thefour thefive thesix' Total parameter number is ==> 2 Your whole parameter is ==> 'thefive thesix' if then
简单的版本：
if [条件判断式]; then 条件判断式成立时，进行的命令工作内容； fi cat ans_yn-2.sh 输出： #!/bin/bash #Program: # This program shows the user's choice #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH read -p "Please input (Y/N):" yn if [ "${yn}" == "Y" ] || [ "${yn}" == "y" ]; then echo "OK,continue" exit 0 fi if [ "${yn}" == "N" ] || [ "${yn}" == "n" ]; then echo "Oh,interrupt!" exit 0 fi echo "I donot know what your choice is" && exit 0 复杂的版本：
if [条件判断式]; then 条件判断式成立时，进行的命令工作内容； else 条件判断式不成立时，进行的命令工作内容； fi 更复杂的版本：
if [条件判断式1]; then 条件判断式1成立时，进行的命令工作内容； elif [条件判断式2]; then 条件判断式2成立时，进行的命令工作内容； else 条件判断式1和2都不成立时，进行的命令工作内容； fi cat ans_yn-3.sh #!/bin/bash #Program: # This program shows the user's choice #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH read -p "Please input (Y/N):" yn if [ "${yn}" == "Y" ] || [ "${yn}" == "y" ]; then echo "OK,continue" exit 0 elif [ "${yn}" == "N" ] || [ "${yn}" == "n" ]; then echo "Oh,interrupt!" exit 0 else echo "I donot know what your choice is" && exit 0 fi cat hello-2.sh 输出： #!/bin/bash #Program: # This program check $1 is equal to "hello" #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH if [ "${1}" == "hello" ];then echo "Hello,how are you?" elif [ "${1}" == "" ];then echo "You MUST input parameters,ex> { ${0} someword }" else echo "The only parameter is 'hello',ex> {${0} hello}" fi 命令netstat，可以查询到目前主机开启的网络服务端口。
每个端口都有其特定的网络服务，常见的端口与相关网络服务：
| 端口 | 服务 |
|---|---|
| 80 | WWW |
| 22 | ssh |
| 21 | ftp |
| 25 | |
| 111 | RPC（远程过程调用） |
| 631 | CUPS（打印服务功能） |
netstat -tuln 输出： Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN tcp6 0 0 ::1:631 :::* LISTEN tcp6 0 0 ::1:25 :::* LISTEN tcp6 0 0 :::111 :::* LISTEN tcp6 0 0 :::22 :::* LISTEN udp 0 0 0.0.0.0:908 0.0.0.0:* udp 0 0 0.0.0.0:44545 0.0.0.0:* udp 0 0 192.168.122.1:53 0.0.0.0:* udp 0 0 0.0.0.0:67 0.0.0.0:* udp 0 0 0.0.0.0:111 0.0.0.0:* udp 0 0 0.0.0.0:5353 0.0.0.0:* udp6 0 0 :::908 :::* udp6 0 0 :::111 :::* cat netstat.sh 输出： #!/bin/bash #Program: # Using netstat and grep to detect WWW,SSH,FTP and Mail service. #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH # 1. echo "Now,I will detect your linux server's services!" echo -e "The www,ftp,ssh,mail(smtp) will be detect!n" # 2. testfile=/dev/shm/netstat_checking.txt netstat -tuln > ${testfile} testing=$(grep ":80" ${testfile}) if [ "${testing}" != "" ];then echo "WWW is running in your system." fi testing=$(grep ":22" ${testfile}) if [ "${testing}"!="" ];then echo "SSH is running in your system." fi testing=$(grep ":21" ${testfile}) if [ "${testing}"!="" ];then echo "FTP is running in your system." fi testing=$(grep ":25" ${testfile}) if [ "${testing}"!="" ];then echo "MAIL is running in your system." fi 注意：if [ "${testing}" != "" ];then中if与[之间有个空格，不能缺少。
执行情况：
[dj@study bin]$ sh netstat.sh Now,I will detect your linux server's services! The www,ftp,ssh,mail(smtp) will be detect! SSH is running in your system. FTP is running in your system. MAIL is running in your system. case $变量名称 in "第一个变量内容") 程序段 ;; "第二个变量内容") 程序段 ;; *) 程序段 ;; esac *表示其他所有情况。
function fname(){ 程序段 } cat show123.sh 输出： #!/bin/bash #Program: # Use function to repeat information. #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH function printit(){ echo -n "Your choice is " } echo "This program will print your selection!" case ${1} in "one") printit;echo ${1} | tr 'a-z' 'A-Z' ;; "two") printit;echo ${1} | tr 'a-z' 'A-Z' ;; "three") printit;echo ${1} | tr 'a-z' 'A-Z' ;; *) echo "Usage ${0} {one|two|three}" ;; esac 函数function内部也有$0 $1 $2...这种变量，容易与shell脚本的$0 $1 $2...搞混.
while [ condition ] do 程序段落 done until [ condition ] do 程序段落 done 使用while：
cat yes_to_stop.sh 输出： #!/bin/bash #Program: # Repeat question until user input correct answer. #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH while [ "${yn}" != "yes" -a "${yn}" != "YES" ] do read -p "Please input yes/YES to stop this program: " yn done echo "OK! you input the correct answer." 使用until：
cat yes_to_stop-2.sh 输出： #!/bin/bash #Program: # Repeat question until user input correct answer. #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH while [ "${yn}" == "yes" -a "${yn}" == "YES" ] 只需要修改这里为==即可 do read -p "Please input yes/YES to stop this program: " yn done echo "OK! you input the correct answer." cat cal_1_100.sh 输出： #!/bin/bash #Program: # Use loop to calculate "1+2+3+4+5+...+100" result. #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH s=0 i=0 while [ "${i}" != "100" ] do i=$(($i + 1)) s=$(($s+$i)) done echo "The result of '1+2+3+...+100' is ==> $s" 执行情况：
sh cal_1_100.sh 输出： The result of '1+2+3+...+100' is ==> 5050 cat cal_1_100.sh 输出： #!/bin/bash #Program: # User input n,I will use loop to calculate "1+2+3+4+5+...+n" result. #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH read -p "Please input n:" n s=0 i=0 while [ "${i}" != "${n}" ] do i=$(($i + 1)) s=$(($s+$i)) done echo "The result of '1+2+3+...+ '${n} is ==> $s" 执行情况：
sh cal_1_100.sh Please input n:10 The result of '1+2+3+...+ '10 is ==> 55 前面while和until都是必须要符合某个条件，而for是已知要进行几次循环。
for var in con1 con2 con3... do 程序段 done 通过管道命令的cut识别出单纯的账号名称，以id分别检查用户的标识符与特殊参数。
cat userid.sh 输出： #!/bin/bash #Program: # Use id,finger command to check system account's information. #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH users=$(cut -d ':' -f1 /etc/passwd) for username in ${users} do id ${username} done sh userid.sh 输出： uid=0(root) gid=0(root) 组=0(root) uid=1(bin) gid=1(bin) 组=1(bin) uid=2(daemon) gid=2(daemon) 组=2(daemon) uid=3(adm) gid=4(adm) 组=4(adm) ... uid=38(ntp) gid=38(ntp) 组=38(ntp) uid=72(tcpdump) gid=72(tcpdump) 组=72(tcpdump) uid=1000(dj) gid=1000(dj) 组=1000(dj),10(wheel) cat pingip.sh 输出： #!/bin/bash #Program: # Use ping command to check the network's PC state. #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH network="192.168.1" for sitenu in $(seq 1 100) do ping -c 1 -w 1 ${network}.${sitenu} &> /dev/null && result=0 || result=1 if [ "${result}" == 0 ];then echo "Server ${network}.${sitenu} is UP." else echo "Server ${network}.${sitenu} is DOWN." fi done 此处， $(seq 1 100)可以用{1..100}替换。类似的，连续输出a-g的字符，echo {a..g}。
cat dir_perm.sh 输出： #!/bin/bash #Program: # User input dir name,I find the permission of files. #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH # 1. read -p "Please input a directory: " dir if [ "${dir}" == "" -o ! -d "${dir}" ];then echo "The ${dir} is NOT exist in your system." exit 1 fi # 2. filelist=$(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 ${perm}" done 执行情况：
sh dir_perm.sh 输出： Please input a directory: /home/dj The file /home/dj/a2's permission is readable writable executable The file /home/dj/bin's permission is readable writable executable The file /home/dj/catfile's permission is readable writable The file /home/dj/homefile's permission is readable writable The file /home/dj/last.list's permission is readable writable The file /home/dj/list_error's permission is readable writable The file /home/dj/list_right's permission is readable writable The file /home/dj/regular_express.txt's permission is readable writable The file /home/dj/公共's permission is readable writable executable The file /home/dj/模板's permission is readable writable executable The file /home/dj/视频's permission is readable writable executable The file /home/dj/图片's permission is readable writable executable The file /home/dj/文档's permission is readable writable executable The file /home/dj/下载's permission is readable writable executable The file /home/dj/音乐's permission is readable writable executable The file /home/dj/桌面's permission is readable writable executable for (( 初始值;限制值;赋值运算 )) do 程序段 done cat cal_1_100-2.sh 输出： #!/bin/bash #Program: # Try to calculate 1+2+3+...+${your_input} #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH read -p "Please input a number, I will count for 1+2+3+...+your_input:" nu s=0 for (( i=1;i<=${nu};i=i+1 )) do s=$((${s}+${i})) done echo "The result of '1+2+3+...+${nu}' is ==> ${s}" 执行情况：
sh cal_1_100-2.sh 输出： Please input a number, I will count for 1+2+3+...+your_input:10 The result of '1+2+3+...+10' is ==> 55 这里面的逻辑有些理不顺，后续继续学习。
cat what_to_eat.sh 输出： #!/bin/bash #Program: # Try do tell you what you may eat. #History: #2020/06/08 dj First release PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin export PATH eat[1]="maidangdanghanbao1" eat[2]="maidangdanghanbao2" eat[3]="maidangdanghanbao3" eat[4]="maidangdanghanbao4" eat[5]="maidangdanghanbao5" eat[6]="maidangdanghanbao6" eatnum=6 eated=0 while [ "${eated}" -lt 3 ];do check=$(( ${RANDOM} * ${eatnum} / 32767 + 1)) mycheck=0 if [ "${eated}" -ge 1 ];then for i in $(seq 1 ${eated}) do if [ ${eatedcon[$i]} == $check ];then mycheck=1 fi done fi if [ ${mycheck} == 0 ];then echo "you may eat ${eat[${check}]}" eated=$(( ${eated} + 1 )) eatedcon[${eated}]=${check} fi done 运行情况：
sh what_to_eat.sh you may eat maidangdanghanbao1 you may eat maidangdanghanbao4 you may eat maidangdanghanbao5 sh [-nvx] scripts.sh -n 不要执行脚本，仅检查语法问题 -v 在执行脚本前，现将脚本文件内容输出到屏幕上 -x 将使用到的脚本内容显示到屏幕上（相当有用） sh -x scripts.sh 进行程序的debug
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