Start mysql service if not running
Here is the simple shell script check the MySQL service status, if MySQL service is not running then start MySQL service.
#!/bin/bash SERVICE='mysql' if ps ax | grep -v grep | grep $SERVICE > /dev/null then echo "$SERVICE service is running." else echo "$SERVICE is not running" service mysqld start fi
Let me describe about the command we use here. Specially why we are using grep -v grep.
grep -v :
When you want to display the lines which does not matches the given string/pattern, use the option -v as shown below
grep -v grep:
This option will exclude all “grep” command from running process list.
“grep -v grep” help here to exclude “grep mysql” from console. If mysql services is stopped and someone runs “ps ax | grep mysql” then command “ps ax | grep mysql” will fail here.
Example Output :
$ ps ax | grep mysql ------------------------ 3456 pts/1 S 0:00 /bin/sh /usr/bin/mysqld_safe --datadir=/var/lib/mysql --socket=/var/lib/mysql/mysql.sock --pid-file=/var/run/mysqld/mysqld.pid --basedir=/usr --user=mysql 5634 pts/1 Sl 0:01 /usr/libexec/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql --log-error=/var/log/mysqld.log --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/lib/mysql/mysql.sock 6433 pts/1 S+ 0:00 grep mysql $ ps ax | grep -v grep | grep mysql 4395 pts/1 S 0:00 /bin/sh /usr/bin/mysqld_safe --datadir=/var/lib/mysql --socket=/var/lib/mysql/mysql.sock --pid-file=/var/run/mysqld/mysqld.pid --basedir=/usr --user=mysql 4497 pts/1 Sl 0:01 /usr/libexec/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql --log-error=/var/log/mysqld.log --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/lib/mysql/mysql.sock
“>/dev/null” in ‘if’ statement
“if” doesn’t need output of the grep. It only require some lines matching the condition but not the output of the grep command. So I have redirected grep output to /dev/null.
https://github.com/roopendra/devops/tree/master/bash_scripting
