select elements in a list

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

Dear Wise Monks,

I would like , when I open a file, to select some elements

Here is my start file

AAD;   ;CCR;365
TEC;UTF;TDE;450
TRE;   ;FTE;164
TEC;URT;TDE;687
ERT;   ;ETR;567
TEC;UGC;TDE;687
[download]

I would like to work only on the lines for which the second element is not empty, that means the following lines :

TEC;UTF;TDE;450
TEC;URT;TDE;687
TEC;UGC;TDE;687
[download]

Could you tell me where did I go wrong? Thanks

#!/usr/bin/perl
use strict;
use warnings;
use diagnostics;

# la commade "use strict" permet d'être plus rigoureux

##############################################
# TASKS MADE BY THE SCRIPT 
##############################################

# the task of this script is to look for the following aircraft_id

##################################
##  ARGUMENTS OF THE SCRIPT 
##################################

#####################################
# do not forget the $ before the ARGV
#####################################


#  THE FIRST ARGUMENT :
# we have to give the name of the regulation which will help us to ope
+n the first file
# the name of the first file to open is :  Regulation_Slot_List_${reg_
+id}
my ${Reg_Id} = "$ARGV[0]";


################# END OF THE DECLARATION OF THE ARGUMENTS

#################  IN WHICH DIRECTORY WE ARE ########################

my $Current_Dir = `pwd`;
print STDOUT "the current directory is $Current_Dir";

#####################################################################



################### OPEN THE ANALYSIS INFILE #########################
+###
# open the first file 
# do not forget the "" to declare  my ${analysis_file} = 

my ${analysis_file} = "Analysis_Regulation_Slot_List_${Reg_Id}_last.cs
+v";
open(INFILE,"${analysis_file}") or die "Can't open ${analysis_file} : 
+$!";
######################################################################
+#####


################### OPEN THE OUTFILE ############################
# open the first file 
# do not forget the "" to declare  my ${analysis_file} = 

my $outfile = "with_ALL_FT_${analysis_file}";

open(OUTFILE,">${outfile}") or die "Can't open ${outfile} : $!";
######################################################################
+#####





# we want to skip the first line of the INFILE
<INFILE>;

    while (<INFILE>){
    
    my @Elements = split(/;/,$_);    
    
        if ($Elements[1] ne '   '){
        print OUTFILE "$_";
        }
    }
close INFILE;
close OUTFILE;
[download]

update : proposition of code

Comment on select elements in a list Select or Download Code

Replies are listed 'Best First'.
Re: select elements in a list by FunkyMonk (Bishop) on Aug 06, 2007 at 14:24 UTC
split each line on `;` and test if the second element in the list is 3 spaces: `my @interesting = grep { (split /;/)[1] ne ' ' } <DATA>; print @interesting; __DATA__ AAD; ;CCR;365 TEC;UTF;TDE;450 TRE; ;FTE;164 TEC;URT;TDE;687 ERT; ;ETR;567 TEC;UGC;TDE;687` [download] Output: `TEC;UTF;TDE;450 TEC;URT;TDE;687 TEC;UGC;TDE;687` [download] Not nearly as much fun as your previous question!	[reply] [d/l] [select]
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Re: select elements in a list by Fletch (Bishop) on Aug 06, 2007 at 14:23 UTC
Use grep on the results of splitting your source lines on `;`. If you just want to filter the file judicious use of the `-F`, `-a`, and `-n` options (see perlrun) for a one-liner would do the trick.	[reply] [d/l] [select]
Re: select elements in a list by toolic (Bishop) on Aug 06, 2007 at 14:27 UTC
This code demonstrates some basics about opening and closing a file, using a regular expression to search for specific lines, and using strictures (warnings/strict) to enforce good coding practices. `#!/usr/bin/env perl use warnings; use strict; open my $fh, '<', 'foo.txt' or die "Can not open file: foo.txt: $!\n"; while (<$fh>) { if (/^\w{3};\w/) { print; # or do whatever you need to do... } } close $fh or die "Can not close file: foo.txt: $!\n";` [download] Here is the output, assuming "foo.txt" is your start file: `TEC;UTF;TDE;450 TEC;URT;TDE;687 TEC;UGC;TDE;687` [download]	[reply] [d/l] [select]
Re: select elements in a list by hilitai (Monk) on Aug 06, 2007 at 14:26 UTC
Well, here's a 10-second version: `#!/usr/bin/perl use strict; use warnings; use diagnostics; my $file = shift; open (F,"<$file") or die "Can't open $file: $!"; while (<F>) { $_ !~ /;\s+;/ and print $_; }` [download]	[reply] [d/l]
Re: select elements in a list by merlyn (Sage) on Aug 07, 2007 at 17:25 UTC
Just zeroing in on something nobody else has yet commented on, you have: my $Current_Dir = `pwd`; print STDOUT "the current directory is $Current_Dir"; [download] First, if you're using pwd like that, you should chomp it. The directory name doesn't end in a newline (normally), but the output of pwd has an extra newline on the end. This would have broken things later had you done something like: `open my $output, ">", "$Current_Dir/foo.txt";` [download] as the extra newline would have caused the directory to not be found. Second, you could have used Cwd, which is a core module, and done this much faster and more reliably: `use Cwd; my $Current_Dir = getcwd; print STDOUT "the current directory is $Current_Dir\n";` [download] -- Randal L. Schwartz, Perl hacker	[reply] [d/l] [select]