Shell Programming and Scripting

You can do it entirely in the shell, using no external commands:

Code:

read -r line < "$FILE"

var=${line#*$}
var=${var#*{}
var=${var%%[!a-zA-Z_0-9]*}

echo "$var"

Or you can use sed.

Code:

sed 's/[^$]*${*\([a-zA-Z_0-9]*\)}*.*/\1/' "$FILE"

Or you can use awk:

Code:

awk -F '$' '{
  gsub( /[{}]/,"", $2 )
  gsub( /[^a-zA-Z_0-9].*/,"", $2)
  print $2 }
' "$FILE"

These scripts all find the first variable in the line if there is more than one.

Hmmm...I'm not great at explaining but here goes...

Think of \1, \2, \3, ..., \n as "place-holders". This is where results from your searching are placed.

In sed, you can assign a result to a "place holder" by using \(<regexp>\). If you have 3 \(<regexp>\) then you'll have 3 "place-holders" that is if they have a result...



So the \1 means:

\1 - result of this \([A-Za-z0-9]\{1,\}\).


Aaaarrrrggghhhh!!! I just can't explain it enough, man . Check the ff. and I hope they give a more detailed explanation:


http://www.grymoire.com/Unix/Sed.html#uh-4

Regular-Expressions.info - Regex Tutorial, Examples and Reference - Regexp Patterns