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Help with xargs

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# 8  
Old 03-17-2013
Try this:

Code:
set -- a b c
echo $1
echo $2
echo $3
echo "$*"
IFS="|"
echo "$*"

and you'll see what I'm doing.
# 9  
Old 03-18-2013
That was really helpful for me to understand what is going on here. So, I see what's happening but I'm still not sure of the purpose of the IFS command is. I see what it is doing, setting the delimiter to |. But what purpose does that serve for the remainder of the script? Somehow it must have an effect when running the last line.
Code:
netstat -nlp | egrep "($*)/"

# 10  
Old 03-18-2013
It's not a command, it's a special variable which determines what value(s) the shell splits and joins strings upon. Setting it to | allows me to join $1 $2 $3 ... together like "A|B|C" so I can grep for more than one thing at once -- that being the syntax egrep uses for multiple search strings. plain grep doesn't have that.

egrep also lets you group things with (). So It searches for (PID1|PID2|PID3)/, so PID1/, or PID2/, or PID3/. That way it won't accidentally match a number elsewhere in netstat, it will just look for them in the PID field where they belong.
This User Gave Thanks to Corona688 For This Post:
axiopisty
# 11  
Old 03-18-2013
Nice! Thank you for your help. Here is my final solution. If you have any suggestions please let me know. I didn't end up using awk the way you suggested because I couldn't get it to work.

Code:
$ cat portsfor 
#!/bin/bash
set -- `ps aux | grep $1 | grep -v grep | grep -v $0 | awk '{print $2}'`
IFS="|"
sudo netstat -nlp | grep -E "($*)/"
$ ./portsfor catalina
[sudo] password for axiopisty: 
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      11389/java      
tcp6       0      0 :::8009                 :::*                    LISTEN      11389/java      
tcp6       0      0 :::8080                 :::*                    LISTEN      11389/java      
tcp6       0      0 127.0.0.1:8005          :::*                    LISTEN      11389/java      
$

Last edited by axiopisty; 03-18-2013 at 01:53 PM.. Reason: changed text
# 12  
Old 03-18-2013
pgrep $1 ought to spit out PIDs (and only PIDs, no filtering needed) matching catalina without matching itself or the script. Use it directly, ps not needed.
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