• 条件判断

test expression

[ expression ]

• 条件表达式中常用的判断

1. 数值 -eq -ne -gt -lt -ge -le [equal not greater than less]
2. 字符串 =: != -z -n [长度zero nozero]
3. 文件 -e -r -w -x -s -d -f -c -b [exist read write execute size directory file char block]

• 语句结构

1. if [ $mark -le 80 ]
2. then
3. echo "Your Grade is Average."
4. elif [ $mark -gt 80 -a $mark -le 90 ]
5. echo "Your Grade is Good."
6. else
7. echo "Your Grade is Outstanding."
8. fi

2. case分支

3. 循环语句

• for循环语句结构

1. for val in vals
2. do
3. ...
4. done

• while循环语句结构

1. i=0
2. while [ $i -le 100 ]
3. do
4. ...
5. ((i=$i+1))
6. done