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Old 02-28-2006, 05:06 AM   #1
furquan
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SED - replace / insert


Hi every one

I am trying to write a script to change variables in a file and also insert additional info in the file.

I am able to do this via the command line using "sed" one by one. But when i try to put all the commands in script i get errors.

Can any one assit.

The code so far is :-

Quote:
#! /bin/bash
sed 's/ali/dubey/' -a sed -e '/user2=santosh/r append.txt' -a sed 's/192.168.9.89/120.78.56.34/' sms.conf
If i type these commands one by on on the command prompt they work fine.

This is for replace :-
Quote:
sed 's/ali/dubey/'sms.conf
This is for the Insert in a location :-
Quote:
sed -e '/user2=santosh/r append.txt' sms.conf
This is again replace :-
Quote:
sed 's/192.168.9.89/120.78.56.34/' sms.conf
but once i club it together in a script it does not work accordingly.

Any assistance ???

Thanks
 
Old 02-28-2006, 05:53 AM   #2
bigearsbilly
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do in a proper sed script maybe?

Code:
#!/usr/bin/sed -f

s/this/that/
s/THIS/THAT/g
etc etc...
 
Old 02-28-2006, 06:23 AM   #3
jschiwal
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You need the '-e' option for every sed command including the first one. Also there isn't an '-a' option in my sed.

For long sed programs, it's best to create a sed script. Especially if you need to use branching, which you will if a pattern can stretch across two or more lines.
 
Old 02-28-2006, 06:28 AM   #4
furquan
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Thanks for the input biily,

but if you could explaing this part a bit more, would be greatful :-

Quote:
#!/usr/bin/sed -f

s/this/that/
s/THIS/THAT/g
Thanks
 
Old 02-28-2006, 06:32 AM   #5
furquan
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Hi jschiwal,

I used "-a" for "and". Could you tell me why do we need -e for every sed statement ?

Also could you tell me more about sed scripts.

Thanks
 
Old 03-01-2006, 06:58 PM   #6
jschiwal
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fixed typo

I think that you are mixing in the syntax for the find command. The -e option allows you to enter more than one sed command. For example, suppose that you want to change every occurance of the word 'furquan' to 'Furquan' in a document, and also remove all blank lines.
sed -i -e 's/furquan/Furquan/g' -e '/^$/d' document

This is the same as having a sed scripts "changes.sed" with the contents:
s/furquan/Furquan/g
/^$/d

You would call this script like: sed -f changes.sed document

For some types of editing with sed, you have to use branches, and so you will need a sed script. Using a single
sed command with -e is best for simple changes.

I'll give you an example. Suppose that you use k3b to back up files in /home/username/Documents/ and you want to get rid of them. If you unzip the .k3b file you saved there will be a "mimetype" file and a "maindata.xml" file.
Examining the contents, you notice that the full pathname for each file is included in this document, but that the lines look like:
<url>/home/username/Documents/aDocument.pdf</url>
So you would like to A) remove all lines that don't match this pattern and B) remove the <url> and </url> part. So only 2 sed commands are necessary and you can put them in the same sed command and pipe the output to xargs.

sed -e '/^<url>/!d' -e 's/^<url>\(.*\)<\/url>/\1/' maindata.xml | tr '\n' '\000' | xargs -0 rm

The first command deletes all lines that don't start with '<url>'. The second command removes the <url> and </url> tags. The <url> and <\/url> parts in the search command serve as anchors, while the \(.*\) is a wild card that saves the contents in the middle. The \1 recalls the pattern found in the replace section of the sed substitute 's' command. The tr command replaces new-lines with null characters to make it easier to handle filenames that contain spaces.

The -e option is also used by the grep command. Suppose that you use the "locate" command but several screens are displayed. You can remove lines by piping the output through "grep":
locate pattern | grep -v -e pattern1 -e pattern2 -e pattern3

This way, you can press the up arrow, and keep adding patterns until you have the response pruned to how you want it.

Last edited by jschiwal; 03-04-2006 at 12:45 AM.
 
  


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