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How do I parse and evaluate a file line-by-line?

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Contributed by kendroid on Mar 03, 2001 at 08:12 UTC
Q&A  > files


Description:

My question is similar to this one, but I'm pretty much a newbie so I have a question in addition: I understand how to throw a file line-by-line into an array, but how could I search the array for "Down" in one element and "Up" in a following (not necessarily the next) element? I'm trying to generate stats from a router log that looks something like this:
a_time_down Down a_time_up Up a_time_down Down a_time_down Down a_time_up Up
I have to come up with a aggregate downtime from a log like this. I found Time::ParseDate (what a blessing!), so once I know which Down element cooresponds with the next Up, tallying up the downtime shouldn't be a problem. Thanks so much for your help; I'm pretty new to Perl so please be kind. :)

Answer: How do I parse and evaluate a file line-by-line?
contributed by dfog

Assuming that you read in the file into the array using

@lines = <FILE>;
and that the array is already in chronological order, you could loop through matching downs with ups in the following way:
my $count = -1; # set to -1 for loops sake and autoincrementing my $placeHolder = 0; # remembers place in array for the first down my $totalDownTime = 0; while ( $count++ <= $#lines ) { if ( $lines[$count] =~ /Down/ ) # finds first down; { $placeHolder = $count; # the following while increments until it finds the next up, # or the end of the array while ( ( $count++ <= $#lines ) && ( $lines[$count] =~ /Down/ +) ) { # do nothing in the while loop } $totalDownTime += sum( $lines[$placeHolder], $lines[$count] ); # sum will be a function defined by you that takes the lines w +ith # down and its corresponding up, parses them, # and returns the time difference } }

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