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Sed, replace variables in file

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# 1  
Old 05-01-2013
Sed, replace variables in file
Hi Everyone,

I need some help with sed and I'm totally new to it.

I have a template file with variables in it. These variables start with a '$' sign and are exactly one character long (plus the '$' sign). For example: $a, $b, etc.
Each variable should be replaced with the contents of a specific file. As a last step double dollar signs should be replaced with single dollar signs.

Example:

Template file:
Code:
aaaa$abbbb$bcc$$cc

FileA:
Code:
1234

FileB:
Code:
456
789

The result should be:
Code:
aaaa1234bbbb456
789cc$cc

Any help would be appreciated.

Csarli
Last edited by Scrutinizer; 05-01-2013 at 07:34 AM.. Reason: code tags
# 2  
Old 05-01-2013
If you are totally new to sed, I'm not sure this is the best problem to start on. But it doesn't matter. Smilie Here is one way to do it:
Code:
$ cat test.sh
# : is chosen as a special character not otherwise in any of the files
fileA=`tr "\n" ":" < fileA | sed "s/:$//"`
fileB=`tr "\n" ":" < fileB | sed "s/:$//"`
sed -e "s/\$a/$fileA/g" -e "s/\$b/$fileB/g" -e 's/$\$/$/g' template | tr ":" "\n"

Code:
$ ./test.sh
aaaa1234bbbb456
789cc$cc

# 3  
Old 05-01-2013
Please use code tags as required by forum rules!

Assuming you are using bash; might not work on other, older shells. Although eval is deprecated now and then, it might help in this case, used with caution:
Code:
$ read -d"" a <file1
$ read -d"" b <file2
$ d=$(sed 's:\$\(.\):${\1}:g;s:{$}::' file)
$ eval echo $d
aaaa1234bbbb456
789cc

# 4  
Old 05-01-2013
Thank you very much for your help.

My problem is that all of my files are in HTML. So they are full of special characters. There must be a simpler solution than escaping all of them one by one. At least, I hope so Smilie

And I have to do this on openwrt, so I only have busybox.
Anyway, I don't insist on sed if there is a better solution.
# 5  
Old 05-01-2013
Second output line supposed to be 789cc$cc
This User Gave Thanks to hanson44 For This Post:
RudiC
# 6  
Old 05-01-2013
Thanks. Replace s:{$}::by s:${$}:\$:.
This User Gave Thanks to RudiC For This Post:
csarli2006
# 7  
Old 05-01-2013
Quote:
My problem is that all of my files are in HTML.
So they are full of special characters.
OK. There is the backtick ` which I would guess is not in your HTML files, as an alternative to : character.

Or, here is an alternative that uses \f formfeed for the special character, which should 100% not be in your HTML files. If it is in there for some reason, it can easily be removed with tr -d "\f" before running the rest of the script.
Code:
$ cat test.sh
# \f formfeed is chosen as special character not otherwise in any of the files
fileA=`tr "\n" "\f" < fileA | sed "s/\f$//"`
fileB=`tr "\n" "\f" < fileB | sed "s/\f$//"`
sed -e "s/\$a/$fileA/g" -e "s/\$b/$fileB/g" -e 's/$\$/$/g' template | tr "\f" "\n"

Code:
$ ./test.sh
aaaa1234bbbb456
789cc$cc

Quote:
There must be a simpler solution than escaping all of them one by one.
Maybe someone else can come up with a simpler solution. It will be interesting to see. In the meantime, what if you try this solution and the RudiC solution on your real files.
This User Gave Thanks to hanson44 For This Post:
csarli2006
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