line replace using a variable in sed

[Glenn Jones]

Hi guys,


I'm trying to replace a line in a file which I've stored to a vriable (I this case I shall call it var1) with another variable (var2). The majority of the script has been written using awk and sed in the c-shell.

Ideally I would like to modify the original file and I've attempted to do this using the following sed command

sed -i 's/"$var1"/"$var2"/' $file

However when I try this nothing changes in the output file $file.

I have tried the command on the command line where I put $var1 and $var2 in explicitly. This does work so the problem is getting the script to read $var1 and $var2.

If anyone could help it will be much appreciated. I'm using gsed version 4.1.4 if thats any help

Thanks

[Dill]

Try enclosing the entire expression with quotation marks, like so:


sed -i "s/$VAR_1/VAR_2/g" $FILE

Cheers,
Dill

[Glenn Jones]

Try enclosing the entire expression with quotation marks, like so:


sed -i "s/$VAR_1/VAR_2/g" $FILE

Cheers,
Dill

Thanks Dill.

I've just given that command a go, but it gives me the following error:



gsed: -e expression #1, char 27: unknown option to `s'

and deletes $VAR_1 form $FILE

[Dill]

Hmm... the sed FAQ (Section 4.3) had another suggestion:

For longer shell scripts, it is sometimes useful to begin with single quote marks ('), close them upon encountering the variable, enclose the variable name in double quotes ("), and resume with single quotes, closing them at the end of the sed script...


sed -i 's/'"$HELLO"'/'"$WORLD"'/g'

See Section 4 of the FAQ (http://sed.sourceforge.net/sedfaq4.html) for more info.

Hope this helps... and I'm sorry that my first suggestion deleted your variable!

Cheers,
Dill

[ghostdog74]

forget that quoting hell...


var1="hello"
var2="world"
awk -v var1="$var1" -v var2="$var2" '{
gsub(var1,var2)
print
}' file > temp
mv temp file

[Glenn Jones]

Unofrtunatley the sed commands don't seem to work however I do it. I have converted the script into bash to no avail. Not sure what the problem is but I get the following error


gsed: -e expression #1, char 27: unknown option to `s'

where the sed command is


gsed -i 's/'"$event"'/'"$dataPath"'/g' $file1

If anyone else has had this problem I'd be very interested in hearing if and how you overcame this.

I'm now going to give the awk commands a go

Cheers

[uljanow]

eval sed -i 's/$var1/$var2/' $file

[ghostdog74]

eval sed -i 's/$var1/$var2/' $file

why the eval? there's no need to.

[Dan675]

I was having the same problem, looks like mine was due to the fact that the variable I was trying to replace it with was a file path so there was extra forward slashes messing with the sed command.


sed "s/./$workingDirectory/"

I used a different delimiter


sed "s,.,$workingDirectory,"

And it worked, perhaps you where trying to do something similar.