Reading all the files in the directory

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

Hi Monks,

I would like to know how can I read all the files in the directory. The files are of the same format. for eg:

A  B   20 
A  C   15 
C  D   11
A  D   10
C  B   05
[download]

I need to know that how can I take the average of all the values of the column 3 across all the files in the directory and the directory contains more than 100 files.

Thanks.

Comment on Reading all the files in the directory Download Code

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Re: Reading all the files in the directory by toolic (Bishop) on Feb 12, 2010 at 18:34 UTC
Since you have not shown any code, I will assume you are just looking for an approach/algorithm: Create a list of files using either glob or a combination of opendir, readdir, grep and -f. Use a for loop and open each file. Use a while loop to read in each line of the file. split the line and keep a running sum of column 3 values. Also keep track of the number of lines. After all lines of all files have been read, divide the sum by the total number of lines.	[reply]
Re: Reading all the files in the directory by crashtest (Curate) on Feb 12, 2010 at 18:58 UTC
If that's all you need to do, your files are cleanly formatted, and you have a useful shell, you could do it in a one-liner: `$ perl -nlae "$t+=$F[2]; END{print $t/$.}" *` [download] (see perlrun to understand the `-a`, `-n`, `-l` and `-e` options.) For a more flexible (and verbose) approach, the following could be a useful skeleton for your code: use strict; use warnings; use File::Find; sub process_file{ return unless (-f); # Only work on files, not directo +ries open INPUT, '<', $_ or die "Couldn't open $_: $!"; while (<INPUT>){ # works through the file line-by- +line chomp; # delete trailing new line my @columns = split /\s+/; # split on whitespace print "TODO: Process the following columns: ", join(" -- " => @columns), "\n"; } close INPUT or die $!; } # Find any file in a directory named "data", for example # (and its subdirectories) find(\&process_file, 'data'); [download] I am using File::Find in this example to process files. There are other ways to approach this.	[reply] [d/l] [select]