Question

Here’s a problem I ran into recently. I have attributes strings of the form

'x=1 and y=abc and z=c4g and ...' 

Some attributes have numeric values, some have alpha values, some have mixed, some have dates, etc.

Every string is supposed to have ‘x=someval and y=anotherval‘ at the beginning, but some don’t. I have three things I need to do.

1. Validate the strings to be certain that they have x and y.
2. Actually parse the values for x and y.
3. Get the rest of the string.

Given the example at the top, this would result in the following variables:

$x = 1; $y = 'abc'; $remainder = 'z=c4g and ...' 

My question is: Is there a (reasonably) simple way to parse these and validate with a single regular expression? i.e.:

if ($str =~ /someexpression/) {     $x = $1;     $y = $2;     $remainder = $3; } 

Note that the string may consist of only x and y attributes. This is a valid string.

I’ll post my solution as an answer, but it doesn’t meet my single-regex preference.

Answer 1

I’m not the best at regular expressions, but this seems pretty close to what you’re looking for:

/x=(.+) and y=([^ ]+)( and (.*))?/ 

Except you use $1, $2, and $4. In use:

my @strs = ('x=1 and y=abc and z=c4g and w=v4l',             'x=yes and y=no',             'z=nox and w=noy');  foreach (@strs) {     if ($_ =~ /x=(.+) and y=([^ ]+)( and (.*))?/) {         $x = $1;         $y = $2;         $remainder = $4;         print 'x: $x; y: $y; remainder: $remainder\n';     } else {         print 'Failed.\n';     } } 

Output:

x: 1; y: abc; remainder: z=c4g and w=v4l x: yes; y: no; remainder:  Failed. 

This of course leaves out plenty of error checking, and I don’t know everything about your inputs, but this seems to work.