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Old 01-17-2008, 08:23 PM   #1
stlouis
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Another SED Syntax Question...


Hi everyone,

I have another sed question for everyone... I'm having a bit of troubles with something, and it's really becoming frustrating...

I'm trying to do the following:

I have a plain text table that has entries in the following format:


26:<IP_ADDRESS>
27:<IP_ADDRESS>

and so on....

The 26 and 27, etc... at the beginning are just User Numbers

Since users ip's are dynamic, they are always changing, so I needed a way to keep this table updated when the user log's on. So I'm writing a script that will be run from the user's .bash_profile at login, which will update this table.

There is a constant variable, lets say $myuser which returns the appropriate usernumber, eg. 26, 27, 28, etc....

I defined a variable called $myip which obtains the user's IP Address in the following way:

myip=`echo $SSH_CLIENT | awk '{print $1}'`

Now I was going to use sed to update the table, by searching for the constant variable, which is the usernumber, the replace the existing IP Address with the new one, if it is different. Even if it just updates the substitutes the IP, regardless if it changed or not, avoiding the additional check would be OK, as the system has a handful of users.

The problem is, I can't seem to figure out the proper syntax for doing this with sed.

eg.

26:192.168.2.100 updated to 26:192.168.2.101

With the two variables I'm calling $myip and $myuser and the : , I can't seem to figure out how to do this right...

Sorry if I put more detail than needed, I'm still in the process of learning SED, and didn't want to leave nothing out...

Jeff
 
Old 01-17-2008, 09:27 PM   #2
syg00
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Something likethis might work
Code:
sed -i -e "/$myuser/s/:.* /:$myip /" infile
uses $myuser to address the line you want. Presumes well-formed data - you could easily make the test more robust.
 
Old 01-17-2008, 09:31 PM   #3
angrybanana
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sed:
Code:
myip=192.168.0.69
myuser=9

sed -i "s/^\($myuser:\).*/\1$myip/" tablefile
remove the -i to test it.

Edit: doh, too late.

Last edited by angrybanana; 01-17-2008 at 09:32 PM.
 
Old 01-17-2008, 09:50 PM   #4
stlouis
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Original Poster
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Quote:
sed:

Code:
myip=192.168.0.69
myuser=9

sed -i "s/^\($myuser:\).*/\1$myip/" tablefileremove the -i to test it.

Edit: doh, too late.

Worked like a charm... I had a few examples similar to that, but wasn't using the brackets. Definitely didn't use the -i for testing... I only posted that way for purpose of completeness...
 
  


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