in reply to Is there any efficient way i can take out a specific column from hundreds of files and put it in one file?

It needs a few lines of Perl code only:
use Modern::Perl qw/2014/; use File::Find::Iterator; my $find = File::Find::Iterator->create( dir => ['d:/Perl/scripts'], filter => +\&find ); open my $FH_OUT, '>', './results.CSV' or die "Could not open results f +ile - $!"; while ( my $file = $find->next ) { open my $FH_IN, '<', $file or die "Could not open $file - $!"; say $FH_OUT join ', ', ( split /,/ )[ 0, 2 ] while (<$FH_IN>); } sub find { /GENES\d+\.csv/; }
I tested it with 1000 files of 1000 lines of 10 fields each: Extracting the first and third column and saving them in the results file took 47 seconds on my ASUS tablet with a 1.33 GHz Intel ATOM Z3740 (4 core) processor. I call that very efficient.


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

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