What do these two lines mean?

runnerpaul · 08-12-2008, 10:04 AM

Hey,

Anybody know what these two lines mean

Code:

serverName=`grep $i $confFile|sed 's/^[   ]*\([^=  ]*\)[=    ].*$/\1/g'`
   pid=`ps -efa | grep $serverName|grep -v 'grep '|sed 's/^[^0-9]*\([0-9]*\)[^0-9].*$/\1/'`

Cheers
Paul

burschik · 08-12-2008, 10:19 AM

The first line searches for pattern $i in $confFile and extracts the left hand side of an assignment. The second line searches for a process with a command line (or possibly user name) matching $serverName and extracts the PID. Both lines are examples of pretty bad shell programming.

runnerpaul · 08-13-2008, 08:21 AM

Cheers. I had forgot about this one. Can you tell me what its about?

motoScript=`echo $i|sed 's/^[ ]*$[^= ]*$[= ].*$/\1/g'`

How would I write those lines better?

burschik · 08-13-2008, 08:33 AM

That is basically the same as the first line of your first example. It extracts the left hand of an assignment from a string, which happens to be assigned to the variable "i".

Using grep and then sed in a pipeline is wasteful, since sed can do everything grep can (and then some). The flag "g" in the first line is also unnecessary, since there can only be one replacement as the entire line is replaced. The second line could be replaced by a suitable use of "pgrep".

runnerpaul · 08-14-2008, 06:21 AM

Cheers. Got another one for you. What does the wc -1 mean here?

Code:

cscrpt=`ps -efa |grep $SCRIPTNAME |grep -v 'grep ' |wc -l`

Nylex · 08-14-2008, 06:39 AM

"wc -l" counts the number of lines. You should probably read man pages..

burschik · 08-14-2008, 06:42 AM

"wc -l" counts the lines of output. The statement returns the number of instances of the script named "$SCRIPTNAME" that are running. Again, you could also say something like

Code:

pgrep $SCRIPTNAME | wc -l

runnerpaul · 08-14-2008, 07:57 AM

Instead of returning the number of instances running how could you return the name of the instances running?

burschik · 08-14-2008, 08:47 AM

You already know the name. It is assigned to SCRIPTNAME.

keefaz · 08-14-2008, 08:51 AM

Is it ok ?

Code:

ps -eao comm=