四、流程控制¶
一、if语句¶
1.1 单分支¶
if condition
then
command1
command2
...
commandN
fi
eg:
if [ `ps -ef |grep /usr/sbin/sshd|grep -v grep|wc -l` -eq 1 ];then echo "sshd server exist";fi
二、for循环¶
for var in item1 item2 ... itemN
do
command1
command2
...
commandN
done
eg1:
for i in /*;
do
echo -e " \c";
find $i |wc -l|sort -nr;
done
eg2:
#!/bin/bash
for i in {1..3};
do
echo $i
done
eg3:
#!/bin/bash
for i in "$@"; { # $@是将位置参数作为单个来处理
echo $i
}
默认 for 循环的取值列表是以空白符分隔，也就是第一章讲系统变量里的$IFS:
#!/bin/bash
OLD_IFS=$IFS
IFS=":"
for i in $(head -1 /etc/passwd); do
echo $i
done
#!/bin/bash
for ip in 192.168.1.{1..254}; do
if ping -c 1 $ip >/dev/null; then
echo "$ip OK."
else
echo "$ip NO!"
fi
done
读取文件,判断url可用性
#!/bin/bash
#function:check url
filename=urllist.txt
for url in $(cat $filename)
do
status=`curl -I $url -s|awk '/HTTP/{print $2}'`
if [ $status == "200" ];then
echo "Url:$url is ok!status is $status"
else
echo "Url:$url is error!status is $status"
fi
done
三、while语句¶
格式：
while 条件表达式:do
command
done
eg1:
#!/bin/bash
N=0
while [ $N -lt 5 ]; do
let N++
echo $N
done
条件表达式为 true，将会产生死循环,利用此可以将脚本一直放在后台进行执行 eg2:
#!/bin/bash
IP=10.75.128.8
dir="/DATA/oracle/netdir/"
if [ ! -d ${dir} ];then
mkdir -p ${dir}
fi
echo 1 > ${dir}ping.lock
while true
do
Time=`date +%F`
TIME="${Time} 23:59"
if [ "${data}" == "${TIME}" ];then
mkdir ${dir}${Time} && mv ${dir}ping2.log ${dir}${Time}-ping2.log
mv ${dir}${Time}-ping2.log ${dir}${Time}
fi
find ${dir} -mtime +7 -name "*-ping2.log" -exec rm -rf {} \;
find ${dir} -mtime +7 -type d -exec rm -rf {} \;
data=`date +%F' '%H:%M`
data1=`date +%F' '%H:%M:%S`
echo "------------${data1}---------------">>${dir}ping2.log
ping -c 10 ${IP} >>${dir}ping2.log
if [ $? -eq 1 ];then
STAT=`cat ${dir}ping.lock`
if [ ${STAT} -eq 1 ];then
/usr/bin/python /DATA/oracle/netdir/GFweixin.py xuel GLP-VPN "GLP from PDC(172.16.6.1
50) ping 金融云(10.75.128.8)中断，请检查深信服VPN！ \n TIME:${data1}" echo 0 > ${dir}ping.lock
else
continue
fi
else
STAT=`cat ${dir}ping.lock`
if [ ${STAT} -eq 0 ];then
/usr/bin/python /DATA/oracle/netdir/GFweixin.py xuel GLP-VPN "GLP from PDC(172.16.6.1
50) ping 金融云(10.75.128.8)恢复！ \n TIME:${data1}" echo 1 > ${dir}ping.lock
else
continue
fi
fi
done
文件处理
eg3:
#!/bin/bash
#function:check url
filename=urllist.txt
cat $filename | while read url;do
status=`curl -I $url -s|awk '/HTTP/{print $2}'`
if [ $status == "200" ];then
echo "Url:$url is ok!status is $status"
else
echo "Url:$url is error!status is $status"
fi
done
或
#!/bin/bash
#function:check url
filename=urllist.txt
while read url;
do
status=`curl -I $url -s|awk '/HTTP/{print $2}'`
if [ $status == "200" ];then
echo "Url:$url is ok!status is ${status}"
else
echo "Url:$url is error!status is ${status}"
fi
done <$filename
四、break 和 continue 语句¶
break跳出循环
#!/bin/bash
N=0
while true; do
let N++
if [ $N -eq 5 ]; then
break
fi
echo $N
done
continue
#!/bin/bash
N=0
while [ $N -lt 5 ]; do
let N++
if [ $N -eq 3 ]; then
continue
fi
echo $N
done