setting value of variable in text file

linux_ · 06-11-2012, 07:26 AM

I have a text file which has content like
var1=abcd
var2=efgh
.
.
.
var10=mnop

I want to set the values of these variables from script
With sed it could do it. But, is there any simpler way?

pan64 · 06-11-2012, 07:44 AM

what do you mean by simpler way?
the most simple way is to generate this file in the script.

pixellany · 06-11-2012, 10:52 AM

Code:

sed -r -i 's/var1=[[:alnum:]]+/var1=xyz/' filename

"wherever filename includes "var1=" and at least one letter or number, replace with "var1=xyx""

Seems pretty simple, but I won't promise that it is the absolute simplest....

David the H. · 06-11-2012, 03:07 PM

I think I'd make it even simpler, and just replace the entire line:

Code:

sed -i  '/^var1/c var1=xyz' infile.txt

theNbomr · 06-11-2012, 03:28 PM

Okay, I'm going to get all pedantic here, just to clarify the question.
The OP has a text file with content that looks like a bunch of assignments of values to variables. However, the 'variables' are not really variables until some script that can use that syntax executes it. So the real question is either how to craft a file with the specified content, or how to instantiate the assignments specified in the existing file. There really isn't enough information provided to unambiguously answer the question in either form.

If the OP wants to know how to create a file of the given format, he/she needs to tell us a bit about where the content is supposed to originate.
If the OP wants to instantiate the variables as they are defined in the file, we need to know in what language they are to exist. If we assume they are to become bash variables, then the easy way is to source the file:

Code:

. file.txt

After having done this, the variables will exist with the specified values in that shell. As they are not 'exported', child shells and other processes will not inherit them.

--- rod.

chrism01 · 06-11-2012, 06:47 PM

I think the OP is basically looking at a cfg/data file that can be automatically updated by a feeder script, before being used by another script/program ??
Something like

Code:

feeder.sh updates file.txt

prog reads file.txt and processes

feeder is in loop, repeat from top

Almost like ETL: read DB1 then store results; 2nd prog reads store and eg inserts into DB2

theNbomr · 06-11-2012, 07:40 PM

Reading between the lines, I would guess that's probably what the OP means. That's still a lot of uncertainty. Still, how are we to have any inkling where the variables and respective values are to come from. Surely the data must exist, somewhere, in some form. We need to know more about where and what it looks like.

--- rod.