最近在看 Linux 程序设计，准备写成一个系列。把每天学到的记录下来。 以实际的例子为主。
一、条件语句
if 语句
语法
#用法 1 if condition1 then statement elif condition2 then statement fi #用法 2 if condition1； then statement elif condition2; then statement else statement fi
例子
- case1:
#!/bin/sh echo "Is it moring? Please answer yes or no" read timeofday if [ "$timeofday" = "yes" ]; then echo "Good morning" elif [ "$timeofday" = "no" ]; then echo "Good afternoon" else echo "sorry, $timeofday not recognized. Enter yes or no" exit 1 fi exit 0
case 语句
- case1:
echo "Is it morning? Please input yes or no?" read timeofday case $timeofday in yes) echo "Good morning";; #双分号 no) echo "Good afternoon";; y) echo "Good morning";; n) echo "Good afternoon";; *) echo "Sorry, answer not recognized";; esac
- case2: 合并匹配模式
echo "Is it morning? Please input yes or no?" read timeofday case $timeofday in yes | y | Yes | YES) echo "Good morning";; #双分号 n* | N*) echo "Good afternoon";; *) echo "Sorry, answer not recognized";; esac
- case3: 多条语句
read timeofday case $timeofday in yes | y | Yes | YES) echo "Good morning" echo "Up bright and early in the morning" ;; #双分号 [nN]*) echo "Good afternoon" ;; *) echo "Sorry, answer not recognized" exit 1 ;; esac exit 0
二、循环语句
for 语句
- case1: 固定字符串的for循环
for file in bar fud 43; do echo $file done
- case2: 使用通配符的for循环
for file in $(ls f*.sh); do echo $file done
输出:
bar fud 43
- case3: 以 test1.txt test2.txt ...运行 a.out
for ((i=0; i<200; i++)); do #必须有两个括号 ./a.out < test$i.txt done
+case4: 将当前目录下的所有的.txt改名为 .gif
for file in *.gif do mv $file ${file%%gif}txt //${file%%gif}表示从尾部开始删除与gif匹配的最长部分 done
while 语句
- case1: 密码输入程序
echo "Enter Password" read trythis while [ "$trythis" != "secret" ]; do echo "Sorry, try again" read trythis done echo "Congrats, password correct"
until 语句
与while 相反，当条件不满足时一直运行，直到条件为真
- case1:
read trythis until [ $trythis = "secret" ]; do echo "Sorry, try again" read trythis done
二、其他
And 和 Or
statement && statement statement || statement
语句块
statement && {
statement1
statement2
statement3
...
}
时间： 2024-11-03 03:42:22