Question

probably simple question for someone who knows, but I’m having a hard time retrieving some variable values from a file. My file is something like:

variable1 12
variable2 43
variable3 897

and I want to get the value of variable2, 43.

I tried some commands with sed but with no luck:

sed -n 's/variable2 //;s/variable3//' myFile

Answer 1

With only sed:

$ sed -n 's/^variable2 //p' file
43

Your problem is you are using -n to suppress the output of sed so you need the p flag so sed prints the lines where the substitution took place.

As this just pattern matching I would go with only grep for this:

$ cat file
variable1 12
variable2 43
variable3 897

$ grep -Po '(?<=^variable2 )\d+' file
43

Or even just awk:

$ awk '$1=="variable2"/{print $2}' file
43