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Replace string in a file w/ a variable value

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# 1  
Old 12-08-2008
Replace string in a file w/ a variable value
I am trying to replace the default home page for several mac user accounts, I wrote a script that will hunt the files down and replace them with a pre-configured set. The problem I am having is that the download destination path for the browser is hard coded into a .plist (text config file) file along with the homepage. The issue is that if I replace this file with a pre-configured version the homepage is changed successfully but the download location is then wrong and the browser won't be able to download anything.

the download path originally is something like /Users/rob/Desktop
the altered one is something like /Users/sample/Desktop

Because the /Users/sample/Desktop doesn't match the user I am replacing files for, there is a problem.

So I would like to set the location in the pre-configured file to something like /Users/[PATTERN//PATTERN]/Desktop and have the script open the text file, look for the pattern and replace it with the value of a variable called $USER_NAME which I already have holding the proper user name earlier in the script.

How can I have the script look inside the .plist file, find the pattern and replace it with a variable value?

Thanks,
Rob
# 2  
Old 12-08-2008
Found this on another forum in case anyone is interested, seems straight forward enough.

Quote:
The 'sed' utility is what you want. It can search and replace text using regular expressions. You should be able to 'cat' the resin.conf file into sed, do the replacement, and redirect the output back to resin.conf, something like this:

Code:
cat resin.conf | sed -e 's/ABC/XYZ/' > resin.conf
where ABC is a regular expression matching what you want to find, and XYZ is what you want to replace it with. There's a sed micro-primer in the advanced bash guide that may help you figure out how to insert a variable name into a sed expression.
# 3  
Old 12-08-2008
Ok so the following works...... almost

Code:
cat sample.txt | sed -e 's/abc/xyz/' >> result.txt

The only problem is, I want to use variables instead of abc and xyz

so something like

Code:
SEARCH="REPLACETHISTEXT"
REPLACE="Hello"

cat sample.txt | sed -e 's/$SEARCH/$REPLACE/' >> result.txt

When I try this, nothing happens, are the variables not available due to the pipe? Is there a way around this?

Thanks,
Rob
# 4  
Old 12-08-2008
Code:
SEARCH="REPLACETHISTEXT"
REPLACE="Hello"

cat sample.txt | sed -e "s/$SEARCH/$REPLACE/" >> result.txt

# 5  
Old 12-08-2008
Quote:
Originally Posted by Ikon
Code:
SEARCH="REPLACETHISTEXT"
REPLACE="Hello"

cat sample.txt | sed -e "s/$SEARCH/$REPLACE/" >> result.txt

I actually JUST tried this as a guess and it worked. Can you tell me what difference there is between the single quotes and double quotes that fixes this?

Thanks,
Rob
# 6  
Old 12-08-2008
perl -p -i -e 's/original text string/replacementstring/g' file
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