Re: Create Arrays On-the-Fly

You can have an array of hash refs instead.

@clients = (
    { MAC => $mac, RSSI => $rssi, SNR => $snr }, /* 0 */
    { MAC => $secondmac, RSSI => $secondrssi, SNR => $secondsnr }, /* 
+1 */
    /* etc */
);
[download]

Then you can grab the bits like

%client_0 = %{$clients[0]};
[download]

etc.

To build it on the fly, you'd have code like:

my @clients;

# The whole hash at once
$clients[0] = { MAC => $mac, /* ... */ };

# Or setting individual bits
$clients[0]->{MAC} = $mac;
[download]

This is pretty well covered in the documentation, such as in perlreftut and perldsc.

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Re^2: Create Arrays On-the-Fly by spickles (Scribe) on Aug 26, 2009 at 15:27 UTC
fullermd - My issue here is with creating the array and populating it not knowing how many clients I'll have at any one time. So I guess what I'll have to do is output the command to show the currently connected clients to a text file and parse the text file until I reach EOF. Since the file contains words and information other than MAC addresses, I'll know that when I regex match a MAC address, that will be a line to parse and add to the array. Again, I do this until I reach EOF. Thanks!!	[reply]
Re^3: Create Arrays On-the-Fly by fullermd (Priest) on Aug 27, 2009 at 04:39 UTC
Of course, if you're always looking up data by MAC, it could make more sense to structure it as a giant hash, keyed by the MAC, of hash (refs) of the data. That would make looking up particular MAC's faster and a bit cleaner. It may be easier to read too, depending on your own preferences. #!/usr/bin/env perl5 use strict; use warnings; my %clients; my $curmac; while(<DATA>) { chomp; # Assume a format of "Type Data" my ($type, $data) = split / /; # If it's a MAC address, assume later lines refer to this MAC if($type eq "MAC") { $curmac = $data; next; } # RSSI and SNR just get saved $clients{$curmac}{RSSI} = $data if $type eq "RSSI"; $clients{$curmac}{SNR} = $data if $type eq "SNR"; } # Show it use Data::Dumper; print Dumper \%clients; # Find a given entry sub showmacsnr { my $mac = shift; my $ent = $clients{$mac}; if($ent) { print "MAC $mac has SNR $ent->{SNR}\n"; } else { print "Can't find MAC $mac\n"; } } showmacsnr("ba:98:76:54:32:10"); showmacsnr("thi:is:is:nt:re:al"); # Sample data __DATA__ MAC 01:23:45:67:89:ab RSSI 12 SNR 18 MAC ba:98:76:54:32:10 RSSI 7 SNR 3 [download] `% ./tst.pl $VAR1 = { 'ba:98:76:54:32:10' => { 'SNR' => '3', 'RSSI' => '7' }, '01:23:45:67:89:ab' => { 'SNR' => '18', 'RSSI' => '12' } }; MAC ba:98:76:54:32:10 has SNR 3 Can't find MAC thi:is:is:nt:re:al` [download]	[reply] [d/l] [select]
Re^3: Create Arrays On-the-Fly by fullermd (Priest) on Aug 27, 2009 at 04:37 UTC
Right, but you don't have to presize it. Just push entries onto it as you parse them. For instance, to invent a stupid-simple data format, and demonstrate parsing it and doing a thing or two with the data once parsed: #!/usr/bin/env perl5 use strict; use warnings; my @clients; my %tmp; while(<DATA>) { chomp; # Assume a format of "Type Data" my ($type, $data) = split / /; # If it's a MAC address, save off our pre-existing record (if any) +, # and start a new one. if($type eq "MAC") { if(keys %tmp) { # Have to unroll a copy here, otherwise the next line empt +ies # it out. push @clients, { (%tmp) }; %tmp = (); } $tmp{MAC} = $data; } # RSSI and SNR just get saved $tmp{RSSI} = $data if $type eq "RSSI"; $tmp{SNR} = $data if $type eq "SNR"; } # Save the 'last' one if we fell off the end push @clients, \%tmp if keys %tmp; # Show it use Data::Dumper; print Dumper \@clients; # Find a given entry sub showmacsnr { my $mac = shift; my @ba = grep { $_->{MAC} eq $mac } @clients; if(@ba) { my $ent = $ba[0]; print "MAC $mac has SNR $ent->{SNR}\n"; } else { print "Can't find MAC $mac\n"; } } showmacsnr("ba:98:76:54:32:10"); showmacsnr("thi:is:is:nt:re:al"); # Sample data __DATA__ MAC 01:23:45:67:89:ab RSSI 12 SNR 18 MAC ba:98:76:54:32:10 RSSI 7 SNR 3 [download] So you end up with output like: `% ./tst.pl $VAR1 = [ { 'RSSI' => '12', 'SNR' => '18', 'MAC' => '01:23:45:67:89:ab' }, { 'SNR' => '3', 'RSSI' => '7', 'MAC' => 'ba:98:76:54:32:10' } ]; MAC ba:98:76:54:32:10 has SNR 3 Can't find MAC thi:is:is:nt:re:al` [download]	[reply] [d/l] [select]


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