Re^4: Getting File Types data

I have now used your example to give a subroutine to which I give an array of the
extensions for which I want the path to the .exe.
This is below in case it is of any use to another Monk.
Although this works, it would be good if someone could explain how the follwing two
Perl lines work since I do not understand them.

my ( $extention, $type ) = split '=', `assoc $arg_item 2>nul`;
my( undef, $cmd ) = split '=', `ftype $type 2>nul`;
[download]

The sub and test code is below

#! perl -slw
use strict;

#
# sub get_file_association
#
# this gets the path for the given file extension
#
# argument
# 1    $ref_arg reference to array holding the extensions to be tested
# 2    $ref_file_path    reference to the hash holding the .exe asscia
+tions
#            strucutre
#                {extension}{exe} just to the end of the .exe
#                {extension}{all} the whole of the result
# 3    $ref_path    reference to the has holding the path for the exte
+nsion
#            structure
#                {extension}{path<n>} gives all the assciations found
# 4    $ref_error result of finding extensions one of 'none', 'some' a
+nd 'all'
# 5    $ref_error_message acucmulation of error messages (if there are
+ any)
#

sub get_file_association($$$$$) {

my ($ref_arg, $ref_file_path, $ref_file_path_all, $ref_error, $ref_err
+or_message) = @_;

my ($arg_item);
my ($cmd_length, $j, $ord_value, $str, $path_cou, $cur_path, $path_cou
+_str, $add_chr, $path_item);
my ($error_count, @path_split);

$$ref_error = 'none';
$$ref_error_message = '';
$error_count = 0;

foreach $arg_item ( @$ref_arg ) {

    my ( $extention, $type ) = split '=', `assoc $arg_item 2>nul`;

    if(defined($type) == 0) {

        print "No association was found for extension <$arg_item>\n";
        $error_count +=1;
        $$ref_error_message .= "No association was found for extension
+ <$arg_item>\n";

    } else {

           chomp $type;

        my( undef, $cmd ) = split '=', `ftype $type 2>nul`;

        if(defined($cmd) == 0) {

            print "No command was associated with type '$type'";
            $error_count +=1;
            $$ref_error_message .= "No command was associated with typ
+e '$type'";

            chomp $cmd;

        } else {

            print "Extension '$arg_item' is associated with type '$typ
+e' "
                .     "\n\tand the command: <$cmd>\n\n";

            $cur_path = '';
            $path_cou = 0;
            $add_chr = 0;
            $cmd_length = length($cmd);
            for($j = 0; $j < $cmd_length; $j ++) {

                $str = substr($cmd, $j, 1);
                $ord_value = ord(substr($cmd, $j, 1));

                if($ord_value ne 10) {

                    $cur_path .= $str;
                    $add_chr += 1;

                } else {

                    $path_cou += 1;
                    $path_cou_str = 'path' . $path_cou;
                    $ref_file_path_all->{$arg_item}{$path_cou_str} = $
+cur_path;
                    
                    $cur_path = '';
                    $add_chr = 0;

                }
            }

            if($add_chr > 0) {

                $path_cou += 1;
                $path_cou_str = 'path' . $path_cou;
                $ref_file_path_all->{$arg_item}{$path_cou_str} = $cur_
+path;

            }
            foreach $path_item (keys %{$ref_file_path_all->{$arg_item}
+}) {

                $cur_path = $ref_file_path_all->{$arg_item}{$path_item
+};

                if(lc($cur_path) =~ m/\.exe/) {

                    $ref_file_path->{$arg_item}{all} = $cur_path;
                    @path_split = split (/\.exe/, lc($cur_path));
                    $ref_file_path->{$arg_item}{exe} = substr($cur_pat
+h, 0, length($path_split[0])) . '.exe';

                }
            }
        }
    }
}

if($error_count > 0) {

    if($error_count == scalar(@$ref_arg)) {

        $$ref_error = 'all';

    } else {

        $$ref_error = 'some';
    }
}

}


my (@file_ext, %file_path, %file_path_all, $k1, $k2, $error, $error_me
+ssage);

@file_ext = ( '.pl', '.doc', '.csv', '.xls' );
#@file_ext = ( '.pl' , 'xyz');
#@file_ext = ( 'xyz', 'pqr');

get_file_association(\@file_ext, \ %file_path, \%file_path_all, \$erro
+r, \$error_message);

print "\nafter get_file_association - error <$error> message \n$error_
+message\n\n";

foreach $k1 (sort {$a cmp $b} keys %file_path) {

    print "\nextension <$k1>\n";
    print "exe <$file_path{$k1}{exe}>\nall <$file_path{$k1}{all}>\n";

    foreach $k2 (sort {$a cmp $b} keys %{$file_path_all{$k1}}) {

        print "$k2 path <$file_path_all{$k1}{$k2}>\n";
    }
}
[download]

Comment on Re^4: Getting File Types data Select or Download Code

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Re^5: Getting File Types data by BrowserUk (Patriarch) on Aug 21, 2008 at 09:54 UTC
it would be good if someone could explain how the follwing two Perl lines work since I do not understand them. my ( $extention, $type ) = split '=', `assoc $arg_item 2>nul`; my( undef, $cmd ) = split '=', `ftype $type 2>nul`; [download] Essentially both lines do the same thing for the two commands. Breaking those lines down `cmd $arg 2>nul` Where `cmd` is either `assoc` or `ftype`; `$arg` is `$arg_item` or `$type`; and the `2>nul` is command shell (cmd.exe) redirect of stderr to the nul device. The backticks (``) execute the command given passing the argument (`$arg_item` or `$type` respectively), and retrieve the output from those commands, whilst discarding any error messages produced. The output from both commands is in a similar format: `c:\test>assoc .pl .pl=Perl c:\test>ftype Perl Perl="c:\perl\bin\perl.exe" -sw "%1" %*` [download] Ie. `something=this other thing` and the bit you want in both cases is the bit after the = sign. split '=', `...`; so the output of the command is past directly to split which splits the output into two pieces either side of the = and discard the =. `my( $var1, $var2 ) = ...` assigns names to those two pieces. Except that we don't really need the first part as that is just the same as the argument we gave the command. So in one case I chose not to name that part: my( undef, $cmd ) = split '=', `ftype $type 2>nul`; [download] The undef there simply says that I don't really need to name the first part, so it is effectively discarded. Equally, the first line could also do the same thing and become: my ( undef, $type ) = split '=', `assoc $arg_item 2>nul`; [download] Since we never make use of the variable I named `$extension`. Well done for asking. I hope my explanation clarifies things? Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^5: Getting File Types data
by BrowserUk (Patriarch) on Aug 21, 2008 at 09:54 UTC

it would be good if someone could explain how the follwing two Perl lines work since I do not understand them.
my ( $extention, $type ) = split '=', `assoc $arg_item 2>nul`; my( undef, $cmd ) = split '=', `ftype $type 2>nul`;
[download]

Essentially both lines do the same thing for the two commands. Breaking those lines down

`cmd $arg 2>nul`
Where cmd is either assoc or ftype; $arg is $arg_item or $type; and the 2>nul is command shell (cmd.exe) redirect of stderr to the nul device.
The backticks (``) execute the command given passing the argument ($arg_item or $type respectively), and retrieve the output from those commands, whilst discarding any error messages produced.
The output from both commands is in a similar format:
```
c:\test>assoc .pl
.pl=Perl

c:\test>ftype Perl
Perl="c:\perl\bin\perl.exe" -sw "%1" %*
[download]
```
Ie. something=this other thing and the bit you want in both cases is the bit after the = sign.
split '=', `...`; so the output of the command is past directly to split which splits the output into two pieces either side of the = and discard the =.
my( $var1, $var2 ) = ... assigns names to those two pieces.
Except that we don't really need the first part as that is just the same as the argument we gave the command. So in one case I chose not to name that part:
```
my( undef, $cmd ) = split '=', `ftype $type 2>nul`;
[download]
```
The undef there simply says that I don't really need to name the first part, so it is effectively discarded.
Equally, the first line could also do the same thing and become:
```
my ( undef, $type ) = split '=', `assoc $arg_item 2>nul`;
[download]
```
Since we never make use of the variable I named $extension.

Well done for asking. I hope my explanation clarifies things?

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

[reply]
[d/l]
[select]