Replace string in a file w/ a variable value

tret · December 8, 2008, 3:11pm

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

tret · December 8, 2008, 5:19pm

Found this on another forum in case anyone is interested, seems straight forward enough.

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/' &gt; 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.

tret · December 8, 2008, 6:05pm

Ok so the following works...... almost

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

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

Ikon · December 8, 2008, 6:09pm

SEARCH="REPLACETHISTEXT"
REPLACE="Hello"

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

tret · December 8, 2008, 6:17pm

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

squrcles · December 8, 2008, 6:38pm

perl -p -i -e 's/original text string/replacementstring/g' file