Re: Detect Two Strings in File

I think the following program takes care of the edge case too: when you have the first and second word in the right order and then the first word comes again and is not followed anymore by the second word. The OP made clear that he only had to look for the last occurrence of the first word.

use Modern::Perl '2014';

my $first  = qr/STRING/;
my $second = qr/MAGIC/;
my $first_pos;
my $second_pos;

while (<DATA>) {
    $first_pos  = $. if /$first/;
    $second_pos = $. if /$second/;
}

if ( $first_pos and $second_pos > $first_pos ) {
    say "Success! STRING at $first_pos followed by MAGIC at $second_po
+s";
}
else {
    say "Failure! (STRING: $first_pos - MAGIC: $second_pos)";
}

__DATA__
First line
second line
here is the STRING
empty text
the STRING again!
followed by the  MAGIC word
more emptiness
Oh no! the first STRING again
sadness
did we look in vain?
Ah, MAGIC success
[download]

To test the edge case, delete the last line of the DATA-section.

I have assumed that the first and second words cannot happen in the same line.

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

My blog: Imperial Deltronics

Comment on Re: Detect Two Strings in File Select or Download Code

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Re^2: Detect Two Strings in File by omegaweaponZ (Beadle) on Nov 06, 2014 at 14:47 UTC
Sorry to clarify, they absolutely can appear on the same line or may appear on a newline. The only conditions set forth is only the LAST found "string1" needs to be detected. Then from that point foward, find "string2", ignoring everything prior to "string1". If "string2" is not found ON ANY LINE (same or new), yell something. Let me test through a few scenarios and see if I can clarify further. After testing your solution here this does indeed seem to be on the right track. It grabbed the last string1 found and then alerted when it found string2. Oddly enough string2 was found on two different lines, but it detected it on the 2nd line, not the first found. Testing to see if it can be tailored to also detect if on same line UPDATE - Looks like we can add this condition if it appears on the same line by adding this condition in the failure part: `if ($first_pos == $second_pos) { print "Success! (STRING: $first_pos matches same line as MAGIC : $ +second_pos)"; }` [download] So this SHOULD work. Thanks again for the assistance	[reply] [d/l]
Re^3: Detect Two Strings in File by CountZero (Bishop) on Nov 07, 2014 at 05:03 UTC
Yes, that will work if both strings are found on the same line, but does not guarantee that the second string comes after the first string. I have amended my program to take care of this: use Modern::Perl '2014'; my $first = qr/STRING/; my $second = qr/MAGIC/; my $first_pos; my $first_sub_pos; my $second_pos; my $second_sub_pos; while (<DATA>) { do { $first_pos = $.; $first_sub_pos = $-[0] } if /$first/; do { $second_pos = $.; $second_sub_pos = $-[0] } if /$second/; } if ( $first_pos and $second_pos > $first_pos ) { say "Success! STRING at $first_pos followed by MAGIC at $second_po +s"; } elsif ( $first_pos and $second_pos == $first_pos and $second_sub_pos > $first_sub_pos ) { say "Success! STRING (char: $first_sub_pos) followed by MAGIC (char: $seco +nd_sub_pos) at $first_pos"; } else { say "Failure! (STRING: $first_pos / $first_sub_pos - MAGIC: $second_pos / +$second_sub_pos)"; } __DATA__ First line second line here is the STRING empty text the STRING again! followed by the MAGIC word more emptiness Oh no! the first STRING again sadness did we look in vain? Ah, STRING and MAGIC success MAGIC and STRING failed [download] Just add and delete the last lines of the `DATA` section to see the various possibilities. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply] [d/l] [select]