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String stuff

Posted on 2002-06-07
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Last Modified: 2010-03-05
Hi,

I'm very new to Perl so, how would you have something to break this up into like three parts:

<variable name> = <something>

Basically, send each part into a variable where you can have furthur analysis such as whether there was an "=" sign in the input string?

Like is it something like:

$in = <STDIN>;
print "Decl: $in";
while(defined($in))
{
    $in = <STDIN>;
    if(defined($in))
    {
        print "Decl: $in";

        if(!($in contains "="))
        {
            print "Result:\tincorrect - missing equals sign";
        }
    }
}
print "\n\n";

Also, I need it to keep looping into the keyboard input (from input redirection) keeps going until end of input.  I have to do it that ghetto way where I take an input in first.  Can anyone think of a better way?

Thanks!
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Question by:zoomeroo
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  • 3
6 Comments
 
LVL 7

Accepted Solution

by:
yoren earned 400 total points
ID: 7063227
Try this:


print "Enter a variable assignment: ";
while (<STDIN>) {
    chomp; # Strip off the line feed

    if (/([^=]+?)\s*=\s*(.*)/) {
        $name = $1;
        $value = $2;
        print "Name: $name, Value: $value\n";
    }
    else {
        print "Result:\tincorrect - missing equals sign\n";
    }

    print "\nEnter another variable assignment: ";
}
0
 

Author Comment

by:zoomeroo
ID: 7063239
Hi,

Wow.  Do you think you could explain "if (/([^=]+?)\s*=\s*(.*)/) {" a little?

Like how it works?
0
 
LVL 7

Expert Comment

by:yoren
ID: 7063257
Yeah it looks crazy, doesn't it. It's a regular expression. There's a whole section of the Perl Frequently Asked Questions devoted to regular expressions, but here's the translation in English:

/ -- begin a regular expression match
(...) -- match the pattern in the ()'s and put the value in the variable $1 for the first set of ()'s, $2 for the second, etc.

[^=]+ -- match 1 or more characters, anything but an equal sign

? -- don't be greedy, meaning let the next pattern take priority. We use this so you don't include any whitespace before the "=" in the variable name.

\s* -- match zero or more whitespace characters

= -- take a guess

\s* -- more whitespace

(.*) -- match anything else and put it in $2.

/ -- end of regular expression

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Author Comment

by:zoomeroo
ID: 7063262
Ah, nm I understand
0
 

Author Comment

by:zoomeroo
ID: 7063264
How does it know that it goes in $1 and $2?
0
 
LVL 7

Expert Comment

by:yoren
ID: 7063302
$1 holds the value of the first set of parentheses. $2 holds the second. If there was a third set, it would put it in $3, and so on.
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