Start, stop and restart script for a MongoDB server

Question

I have created an start, stop, restart script for a unix-mongodb-server.

It would be nice if you could look over my code and give me some helpful hints on what I could change. I tested the script under my Mac and it works.

This is also available under my GitHub account and available under GitHub -> Mongo_Start_Stop.

VERSION=1.1.2
SCRIPTNAME=$(basename "0ドル")
MONGOHOME=
MONGOBIN=$MONGOHOME/bin
MONGOD=$MONGOBIN/mongod
MONGODBPATH=
MONGODBCONFIG=
if [ $# != 1 ]
then
 echo "Usage: $SCRIPTNAME [start|stop|restart]"
 exit
fi
pid() {
 ps -ef | awk '/[m]ongodb/ {print 2ドル}'
}
stopServer() {
 PID=$(pid)
 if [ ! -z "$PID" ]; 
 then
 echo "... stopping mongodb-server with pid: $PID"
 sudo kill $PID
 else
 echo "... mongodb-server is not running!"
 fi
}
startServer() {
 PID=$(pid)
 if [ ! -z "$PID" ];
 then
 echo "... mongodb-server already running with pid: $PID"
 else
 echo "... starting mongodb-server"
 sudo "$MONGOD" --dbpath "$MONGODBPATH" --config "$MONGODBCONFIG"
 fi
}
restartServer() {
 stopServer
 sleep 1s
 startServer 
}
case "1ドル" in
 start) startServer
 ;;
 stop) stopServer
 ;;
 restart) restartServer
 ;;
 *) echo "unknown command"
 exit
 ;;
esac

Answer 1

Bug

Can you spot the bug on this line?

 PID=$(ps -ef | grep "[m]ongodb" | awk {'print 2ドル'})

The awk script here should be {print 2ドル}, with the curly braces included, so that needs to be within the single-quotes:

 PID=$(ps -ef | grep "[m]ongodb" | awk '{print 2ドル}')

Quoting path variables

It's good to make it a habit to always double-quote path variables in command statements, to protect from globbing and word splitting. Instead of:

SCRIPTNAME=$(basename 0ドル)

Write like this:

SCRIPTNAME=$(basename "0ドル")

The same goes for this line:

 sudo $MONGOD --dbpath $MONGODBPATH --config $MONGODBCONFIG

Useless variable and echo

PID is not used anywhere else inside the script but here:

function isRunning {
 PID=$(ps -ef | grep "[m]ongodb" | awk '{print 2ドル}')
 echo $PID 
}

You could simplify as:

pid() {
 ps -ef | awk '/[m]ongodb/ {print 2ドル}'
}

I also renamed the function, because pid() reflects better its purpose.

User experience

Something's odd in this condition:

rc=$(isRunning)
echo "... stopping mongodb-server with pid: $rc" 
if [ ! -z "$rc" ]; then
sudo kill $rc
fi

If the process is not running $rc will be empty, and users may think the output is weird and the script is buggy. You might want to rearrange this part, for example if the server is not running, then say so.

Make the most of awk

Very often a grep ... | awk ... combo can be simplified, because awk can filter all by itself. Instead of:

PID=$(ps -ef | grep "[m]ongodb" | awk '{print 2ドル}')

You can write:

PID=$(ps -ef | awk '/[m]ongodb/ {print 2ドル}')

Style

This is fine:

function isRunning {
 # ...
}

But the recommended style for function declarations is like this:

isRunning() {
 # ...
}

Variable initialization

This is fine:

MONGOHOME=""
MONGOBIN="$MONGOHOME/bin"
MONGOD="$MONGOBIN/mongod"
MONGODBPATH=""
MONGODBCONFIG=""

But you could write simpler as:

MONGOHOME=
MONGOBIN=$MONGOHOME/bin
MONGOD=$MONGOBIN/mongod
MONGODBPATH=
MONGODBCONFIG=

Redundant semicolon

The semicolon at the end of exit; is redundant, I suggest to remove it:

if [ $# != 1 ]
then
 echo "Usage: $SCRIPTNAME [start|stop|restart]"
 exit;
fi

• Patrick85: Thank you very much. Your comments are very helpfull and i will regard them in future. I also update your comments im my github repository.
• Patrick85: i edited my post with the new code from your review. Did you have a nicer solution with the if-statement? Did you know why i need to use an "slepp 1s" after "stopServer" and then "startServer" ?