(各语法逻辑通用)
1、if语句
结构:
if condition
then
statements
else
statements
fi
2、elif语句(类似c语言中,else if)
二者样例:
#!/bin/sh
echo -n "Is it morning? 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
结果:
Is it morning? Please answer yes or no yes
Good morning
3、if中判断条件注意:
其使用变量时,应该用“”标记。以免出现不合法问题。导致出现 ?:unary operator expected错误
4、for循环
结构:
for variable in values
do
statements
done
样例
#!/bin/sh
for foo in "bar fud 43"
do
echo $foo
done
exit 0
结果:
bar fud 43
5、while语句
结构:
while condition do
statements
done
6、until语句(do…while)
结构:
until condition
do
statements
done
样例:
#!/bin/sh
until who ? grep "$1" > /dev/null
do
sleep 60
done
# now ring
echo -e '\a'
echo *****$1 has just logged in*****
exit 0
结果;
case1 case1~ first for hanshu if tiaojian try_var until useofbianliang has just logged in*****
7、case语句:
结构:
case variable in
pattern [ ? pattern ] ... ) statement;;
pattern [ ? pattern ]... ) statement;;
....
esac
样例:
#!/bin/sh
echo "Is it morning? Please answer yes or no"
read timeofday
case "$timeofday" in
yes) echo "Good morning";;
no ) echo "Good afternoon";;
y ) echo "Good Mornig";;
n ) echo "Good Afternoong";;
* ) echo "Sorry, answer not recognized";;
esac
exit 0
结果:
Is it morning? Please answer yes or no
yes
Good morning
8、其他:与或(&& ||)