第一个shell程序

Love The Way You Lie 2022-03-14 17:42 541阅读 0赞

第一次写shell程序，写了一些简单的代码，稍微介绍一下。

首先程序以\#!/bin/bash指定shell是Bourne Again Shell(shell的一种，若是\#!/bin/tcsh开头则说明指定的是TCshell)，紧接着第二行是一行注释，说明这个程序的功能等，当然可以不写，但是注释是一个良好的编程习惯。后面分别操作了字符串，变量运算，if，case，select，while，for和函数。

\#!/bin/bash

\#this is my first shell  
echo "============string============="  
str="this is my first shell"  
echo "$str"  
echo "==============var=============="  
a=1  
echo "the raw a=$a"  
let "a+=1"  
echo "ater let a=$a"  
a=$\[$a+1\]  
echo "ater \[\] a=$a"  
((a++))  
echo "ater ((++)) a=$a"  
a=$(($a+1))  
echo "ater ((+1)) a=$a"  
a=$(expr $a + 1)  
echo "ater expr a=$a"  
echo "==============if=============="  
echo "input b:"  
read b  
if \[ $b -eq 0 \]  
then  
echo "$b=0"  
elif \[ $b -lt 1 \]  
then  
echo "$b<0"  
else  
echo "$b>0"  
fi  
  
echo "==============case=============="  
echo "input d:"  
read d  
if \[ $d -gt 7 \]  
then  
d=$(($d%7))  
fi  
echo "d=$d"  
case $d in  
1)echo "$d is Monday";;  
2)echo "$d is Tuesday";;  
3)echo "$d is Wednesday";;  
4)echo "$d is Thursday";;  
5)echo "$d is Friday";;  
6)echo "$d is saturday";;  
7)echo "$d is sunday";;  
\*)echo "never come here";;  
esac  
  
echo "==============select=============="  
echo "What is your favourite OS?"  
select var in "Linux" "Windows" "Free BSD" "Other";do  
break;  
done  
echo "You have select $var"  
  
echo "===============while==============="  
echo "input m"  
read m  
\#将sum设置成整形  
typeset -i sum=0  
while \[ $m -gt 0 \]  
do  
sum+=$m  
((m--))  
done  
echo "after while sum=$sum"  
  
echo "================for================"  
sum=0  
for m in 1 2 3 4 5 6 7 8 9;  
do  
sum+=$m  
done  
echo "after for sum=$sum"  
  
echo "==============function=============="  
function show()  
\{  
echo "show function"  
\}  
$(show)  
学习网址：http://wiki.ubuntu.org.cn/Shell%E7%BC%96%E7%A8%8B%E5%9F%BA%E7%A1%80