条件判断式语句

文件类型判断

整数之间的比较

文件权限

字符串判断

多重条件判断

# 两种判断格式
# test -e /root/install.log
# [-e /root/install.log] //推荐[-d /root] && echo "yes" || echo "no"
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单分支if语句

#!/bin/bash

# 判断登陆的用户是否是root
test=$(env | grep "USER" | cut -d "=" -f 2)if [ "$test" == root ]thenecho "Current user is root"
fi
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#!/bin/bash

# 判断分区使用率
rate=$(df -h | grep "/dev/vda1" | awk '{print $5}' | cut -d "%" -f 1)if [ $rate -ge 1 ]thenecho "Warming /dev/vda1 is full !!"
fi复制代码

双分支if语句

#!/bin/bash

read -t 30 -p "Please input a dir: " dirif [ -d "$dir" ]thenecho "yes"elseecho "no"
fi
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#!/bin/bash

#检测apache的运行状态(脚本名字坚决不能包含httpd，否则脚本会失效)
test=$(ps aux | grep httpd | grep -v grep)if [ -n "$test" ]thenecho "$(date) httpd is ok!" >> /tmp/autostart-acc.logelse/etc/rc.d/init.d/httpd start &> /dev/nullecho "$(date) httpd restart httpd!!" >> /tmp/autostart-acc.log
fi
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多分支if语句

#!/bin/bash

read -p "Please input a filename : " fileif [ -z "$file" ]thenecho "Error, please input a filename "exit 1
elif [ ! -e "$file" ]thenecho "Your input is not a file! "exit 2
elif [ -f "$file" ]thenecho "$file is a regulare file!"
elif [ -d "$file" ]then echo "$file is a directory!"
elseecho "$file is an other file!"
fi
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多分支case语句

#!/bin/bash

read -t 30 -p "Please input yes/no : " chocase "$cho" in"yes")echo "yes";;"no")echo "no";;"*")echo "Please input right content";;
esac
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for循环

#!/bin/bash

# 批量解压文件
cd /root/test/
ls *.tar.gz > ls.log
ls *.tgz >> ls.logfor i in $( cat ls.log )dotar -zxf $i & > /dev/nulldonerm -rf ls.log
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#!/bin/bash

s=0
for (( i=1;i<=100;i=i+1 ))dos=$(( $s+$i ))done
echo $s
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#!/bin/bash

# 批量添加指定数量的用户read -p "Please input user name : " -t 30 name
read -p "Please input number of users : " -t 30 num
read -p "Please input user pass : " -t 30 passif [ ! -z "$name" -a ! -z "$num" -a ! -z "$pass" ]theny=$(echo $num | sed 's/[0-9]//g')if [ -z "$y" ]thenfor (( i=1;i<=$num;i=i+1 ))do/usr/sbin/useradd $name$i &> /dev/nullecho $pass | /usr/bin/passwd --stdin $name$i &> /dev/nulldonefi
fi
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#!/bin/bash

#批量删除for i in $( cat /etc/passwd | grep /bin/bash | grep -v root | cut -d ":" -f 1 )douserdel -r $idone
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while循环和until循环

#!/bin/bash

i=1
s=0while [ $i -le 100 ]dos=$(( $s+$i ))i=$(( $i+1))doneecho "This sum is : $s"
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#!/bin/bash

i=1
s=0util [ $i -ge 100 ]dos=$(( $s+$i ))i=$(( $i+1))doneecho "This sum is : $s"
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