Shell Programming and Scripting

Hey guys, thanks all for your replies!

Cool I'll give these a shot and post back...

EDIT:
What I'm doing is this,,, When I run the 'ps' command and I'm looking for a particular process that's running, sometimes there
are multiple instances running of this same process and say for instance 2 of the processes started a day or 2 ago, but that's
all they tell you is the date it started (i.e. the 'ps' command's "STIME"). So what I did was I run "ps -eo pid,etime,cmd" and I get the
elapsed time of the process.
The output of the elapsed column looks like "2-21:44:05", meaning it started 2 days, 21 hours, 44min, and 5 seconds ago. I then use
the time variables from this ETIME column in the output of 'ps' and calculate the other variables I need and feed them into Perl's timelocal
Function with ($sec, $min, $hour, $mday, $month, $year) in order to get a UNIX timestamp for a past date and time.


Thanks Again,
Matt

Hey All,
hopefully someone is still watching this thread, I just had one simple question...

I was just wondering what putting this --> $(...) in double quotes does...?

I searched through the "Bash Cookbook" I have, but I couldn't find any explanation on this...
Also, Googled like crazy but I wasn't able to find anything specifically on this..?

What is the difference between these 2 in the example below?

Code:

### What's the difference between this:
PIDS="$(ps auxww)"

### And this:
PIDS=$(ps auxww)

I tried testing both, and both outputs look the exact same...?
Anyone know the difference?


Thanks in Advance,
Matt

In that case, there doesn't appear to be one, since $( ) doesn't get split. Other things like variables or a literal string would get split without quotes however.

This is because of a feature the bourne shell has. You can set a variable for a single command:

Code:

HTTP_PROXY="localhost:3128" wget http://whatever.com/

The red is the variable, the blue is the command. wget is a command to download webpages, and checks the HTTP_PROXY variable for what proxy to use.

So if you do

Code:

STRING=a b

, it doesn't try to set the string to "a b", it sets STRING=a and tries to run the command b.

Hey Corona688, thanks for the reply.

Ah-ha.... Cool thanks for the explanation, that makes sense!


Thanks Again,
Matt