Simple Totals Example (Help Needed)

doctormaze has asked for the wisdom of the Perl Monks concerning the following question:

In order to learn Perl, I've started fiddling around with text files. I have a file called-

siteperf.txt

, Which contains this data-

 A,5000,20
 B,4500,15
 C,4000,10
[download]

All, I want to do is total the values in the second column.

So far I've come up with this-

 $sitePerf = 'siteperf.txt';
 $tot = 0;
 open(F, "$sitePerf") || die ("Could not open $sitePerf!");
 while (<F>)
 {
  ($siteID, $siteAge, $siteDistance) = (split/,/)[0,1];
  $tot = $hash{$siteID} += $siteAge;
  print $tot;
 }
 close (F);
[download]

, Instead of added the data in the second column ($siteAge) together, the script justs concatenates the values and prints-

500045004000

Your expertise is appreciated,. I've got lots of Perl books out and have been diligently trawling the internet and this is very frustrating!

Thanks

Edited by planetscape - removed code tags from around entire post, replaced with <p></p> tags as appropriate

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Re: Simple Totals Example (Help Needed) by rhesa (Vicar) on Apr 02, 2006 at 22:54 UTC
two things: you should increase $tot, instead of assigning it the current value of $hash{$siteID} you should print $tot outside the while; also, try adding a newline; that would visualise what happens now In code: `while (<F>) { ($siteID, $siteAge, $siteDistance) = (split/,/)[0,1]; $hash{$siteID} += $siteAge; $tot += $siteAge; } print $tot, "\n";` [download] Hope that helps :)	[reply] [d/l]
Re^2: Simple Totals Example (Help Needed) by doctormaze (Initiate) on Apr 02, 2006 at 23:06 UTC
`Thanks, much appreciated!!! };-> p.s. Incredibly quick reply!` [download]	[reply] [d/l]
Re: Simple Totals Example (Help Needed) by McDarren (Abbot) on Apr 02, 2006 at 23:46 UTC
You already have an answer to your question, but as you're new to Perl - here is a little bit of extra advice :) Try to get into the habit of including: `use strict; use warnings;` [download] at the start of every program and script that you write. By useing strict and warnings, you will save yourself many "head-banging" moments. For a good discussion on this, have a read of On Commenting Out 'use strict;' and the ensuing thread. Cheers, Darren :)	[reply] [d/l]
Re: Simple Totals Example (Help Needed) by davido (Cardinal) on Apr 03, 2006 at 06:13 UTC
Here's a "one liner" solution: `perl -naF, -e "$t += $F[1]; eof and print $t;" siteperf.txt` [download] If you wrote that out "the long way", here's how it would look: `while ( <> ) { @F = split ','; $t += $F[1]; eof and print $t; } # Usage: perl mytally.pl siteperf.txt` [download] Within the one-liner, the -n flag is responsible for creating a `while( <> ) {....` loop. The -a flag is responsible for creating a `@F = split ',';` statement. And because the -n loop wraps a loop around all the code, a test must be conducted to spot the end of the file, and print the resulting tally only on the last loop iteration. Can anyone golf the one liner down to fewer keystrokes than this? `perl -naF, -e"$t+=$F[1];eof&&die$t" test.txt` [download] (44, including filename. Choosing a shorter filename doesn't count.) Dave	[reply] [d/l] [select]