LinuxQuestions.org - Extract a substring from a line in a faill

- Programming (https://www.linuxquestions.org/questions/programming-9/)

- - Extract a substring from a line in a faill (https://www.linuxquestions.org/questions/programming-9/extract-a-substring-from-a-line-in-a-faill-775138/)

Extract a substring from a line in a faill

I'm new to linux and bash, and all the awesome utilities linux has, so I'm struggling with the syntax here.

Basically, I have a configuration file that's roughly:

<?php

$var = 'dsfsdf'; //sdfsdf
define('KEY', 'ftyurghj');

//etc.

?>

My goal is to extract the values of $var and 'KEY'

The issues I'm having are A) I'm having a heck of a time escaping some characters like "="

I've done something like this:

sed -ne '/^\$var/p' file.php

And gotten the right line back, but when I go further and try

sed -ne '/^\$var \= /p' file.php

It starts complaining. I would ideally want it to match any whitespace so it could read:

$var ________ = __________ 'blah';

without choking.

and B) I don't know how to capture matches using grep or sed or whatever I need to use

sed -ne '/^\$var \= \'([.*])\'\;/p' file.php

So let's pretend that regex worked (even though it actually just chokes). I want the contents of the parens.

How should I approach this?

just the shell

Code:

while read -r line

do

    case "$line" in

        *\$var*)

            line=${line%%;*}

            val=${line##*=}

            ;;

        *define*)

            line=${line#*\'}

            key=${line%%\'*}

            ;;

    esac

    [ ! -z "$val" -a ! -z "$key" ] && echo "$val: $key" && exit

done <"file"

Code:

sed -n "/<\?php/,/^?>/{ /$var *= */s/\$var *= *'\([^']*\)'.*/\1/p 

                                                                  }" testfile

Escaping the single quote is potentially the trickiest part. I did it here by putting the sed line inside double quotes. The dollar sign also needs to be escaped in the LHS so it is taken literally. You can insert a second line inside the brackets to match define line.

Thanks for the help!

I'm trying to figure out what's going on using my crude knowledge of sed.

The bracket is on a new line, is that necessary?

When I try to use what you wrote, with new line, something strange happens. I paste it in, and without pressing enter, it seems to execute, and it lists all the files in the current directory in 2 columns with a ">" at the end. It repeats that list maybe 2 dozen times (all in less than a second). Don't know what that's about

When I remove the tabs and new line, I just don't get a match, so I execute, get nothing back, and am back at the prompt.

From what I can gather though, you're saying:

use sed, without printing the normal output. We're looking between <?php and ?> for a string matching "/$var *= */s/\$var *= *'$[^']*$'.*/", and we'll grab the first reference we get, and print it.

The pattern is confusing though.

/$var *= */s/\$var *= *'$[^']*$'.*/

Doesn't the $ need to be escaped? What about the =? I get the zero ro more spaces, and I get the reference matching zero or more characters that aren't ', but why does it try to match ".*" after that?

The "/<\?php/,/^?>/" at the beginning defines a range of lines. The brackets "{}" then enclose the sed commands to run when inside that range.

Yes, I should have escaped the "$" but it worked when I tested it and was to lazy to go back and escape it.

I put the closing bracket on another line to emphasize that you could add another line for the line with "define".