分享一个shell脚本的坑：grep匹配+wc取值 在脚本执行后的结果与手动执行结果不一致

打算在跳板机上写一个shell脚本，批量检查远程服务器上的main进程是否在健康运行中。

先找出其中一台远程机器，查看main进程运行情况

[root@two002 tmp]# ps -ef|grep main
root     23448 23422  0 11:40 pts/0    00:00:00 grep --color=auto main

[root@two002 tmp]# ps -ef|grep main|grep -v grep|wc -l
0

shell检查脚本如下

[root@two002 tmp]# cat /tmp/main_check.sh
#!/bin/bash
NUM=$(ps -ef|grep main|grep -v grep|wc -l)
if [ $NUM -eq 0 ];then
echo "It's not good! main is stoped!"
else
echo "Don't worry! main is running!"
fi

执行脚本

[root@two002 tmp]# sh -x /tmp/main_check.sh
++ grep main
++ grep -v grep
++ wc -l
++ ps -ef
+ NUM=2
+ '[' 2 -eq 0 ']'
+ echo 'Don'\''t worry! main is running!'
Don't worry! main is running!

[root@two002 tmp]# sh /tmp/main_check.sh
Don't worry! main is running!

如上执行结果，发现脚本执行过程中，看到赋予NUM参数的结果值是2！但是手动执行ps -ef|grep main|grep -v grep|wc -l的结果明明是0！！
这是由于grep匹配的问题，需要grep进行精准匹配，即"grep -w"。这就需要将main_check.sh脚本内容修改如下：

[root@two002 tmp]# cat /tmp/main_check.sh
#!/bin/bash
NUM=$(ps -ef|grep -w main|grep -v grep|wc -l)
if [ $NUM -eq 0 ];then
echo "Oh!My God! It's broken! main is stoped!"
else
echo "Don't worry! main is running!"
fi

再次执行检查脚本，就OK了

[root@two002 tmp]# sh -x /tmp/main_check.sh
++ grep -w main
++ grep -v grep
++ wc -l
++ ps -ef
+ NUM=0
+ '[' 0 -eq 0 ']'
+ echo 'Oh!My God! It'\''s broken! main is stoped!'
Oh!My God! It's broken! main is stoped!

[root@two002 tmp]# sh /tmp/main_check.sh
Oh!My God! It's broken! main is stoped!

故在跳板机上，批量检查远程服务器的main进程运行状态的脚本为：

[root@tiaoban ~]# cat /usr/bin/main_check
#!/bin/bash
NUM=$(ps -ef|grep -w main|grep -v grep|wc -l)
if [ $NUM -eq 0 ];then
echo "Oh!My God! It's broken! main is stoped!"
else
echo "Don't worry! main is running!"
fi

[root@tiaoban ~]# cat /opt/script/main_check.sh
#!/bin/bash

for i in $(cat /opt/ip.list)
do
/usr/bin/rsync -e "ssh -p22" -avpgolr /usr/bin/main_check $i:/usr/bin/ > /dev/null 2>&1
ssh -p22 root@$i "echo $i;sh /usr/bin/main_check"
done