I/O open()
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From: mmccaws2 on 17 Jan 2007 14:13 Hi I'm trying to understand the I/O open function better. I got the test script to work, but I not sure if the syntax is standard. Could someone explain the syntax option, or point to a link, for using open to run OS commands. use strict; my $line; open (NS_COMMAND, 'nslookup -type=soa wa.gov. ns1.six.net. |') or die "Ooops, $!"; my $count=1; while ($line = <NS_COMMAND>) { chomp($line); print "$count $line\n"; $count++; } close NS_COMMAND; i plan to morph this test script into a routine that runs through of list of nslookup options. Also, since this will be finally ran on [u|li]nux environment then any suggestions specific to the OS would be greatful Oh I need a perl/regex script that filters level 8 interference out of getting work done. Best suggestion gets a embroidery patch with that script on it. Mike
From: Sherm Pendley on 17 Jan 2007 14:30 "mmccaws2" <mmccaws(a)comcast.net> writes: > I'm trying to understand the I/O open function better. Have you read "perldoc perlopentut"? sherm-- -- Web Hosting by West Virginians, for West Virginians: http://wv-www.net Cocoa programming in Perl: http://camelbones.sourceforge.net
From: Paul Lalli on 17 Jan 2007 14:32 mmccaws2 wrote: > I'm trying to understand the I/O open function better. I got the test > script to work, but I not sure if the syntax is standard. Could > someone explain the syntax option, or point to a link, for using open > to run OS commands. perldoc -f open perldoc perlopentut perldoc perlipc > > use strict; Good! > my $line; .... not so good. Declare your variables in the shortest scope possible. It will help immensely in debugging your scripts. > open (NS_COMMAND, 'nslookup -type=soa wa.gov. ns1.six.net. |') > or die "Ooops, $!"; This code is perfectly syntactically valid, but it's not the best. At the very least, you should be using lexical filehandles, rather than global barewords. That way, they're subject to strictures, two independent pieces of code that use the same filehandle name can't interphere with each other, and they're automatically closed when the scope ends. open my $NS_COMMAND, 'nslookup -type=soa wa.gov. ns1.six.net. |') or die "..."; These days, it's also preferred to use the three-argument form of open, rather than specifying the mode within the filename (or program name, in the case of open() for IPC) open my $NS_COMMAND, '-|', 'nslookup', '-type=soa wa.gov.', 'ns1.six.net.' or die "..."; (note that this doesn't really have any effect on your specific case, but it's best to use the best practice always, to get into the habbit. It can affect things greatly when you eventually go to open a file named by a variable whose value was read from the user...) > my $count=1; This variable is pointless, as Perl already defines $. for you... > while ($line = <NS_COMMAND>) { Here, btw, is where $line should have been defined. > chomp($line); > print "$count $line\n"; Why are you chomping only to print a newline at the end anyway? > $count++; > } Taking into account these changes, your loop becomes: while (my $line = <$NS_COMMAND>) { print "$. $line"; } > close NS_COMMAND; > > i plan to morph this test script into a routine that runs through of > list of nslookup options. Also, since this will be finally ran on > [u|li]nux environment then any suggestions specific to the OS would be > greatful No, that's not what you want. You should be asking for suggestions that are platform-agnostic, not simply programs that are not tailored to other operating systems. The above code is indeed platform independent. Paul Lalli
From: Mark Donovan on 17 Jan 2007 15:43 On 1/17/07 12:13, "mmccaws2" <mmccaws(a)comcast.net> wrote: > [snip] > > i plan to morph this test script into a routine that runs through of > list of nslookup options. Also, since this will be finally ran on > [u|li]nux environment then any suggestions specific to the OS would be > greatful > Instead of the nslookup command, the Net::DNS module from CPAN might work for you. See http://www.net-dns.org/ Here's Net::DNS doing the same thing as your nslookup command. === use Net::DNS; use Data::Dumper; # not required, used to show what query returns my $res = Net::DNS::Resolver->new( nameservers => [qw(ns1.six.net)], ); my $query = $res->query('wa.gov', 'SOA') or die "query failed: $res->errorstring"; ($query->answer)[0]->print; print Dumper($query->answer); === This prints: wa.gov. 2711 IN SOA disdns1.wa.gov. bruceh.dis.wa.gov. ( 200701073 ; Serial 10800 ; Refresh 3600 ; Retry 604800 ; Expire 86400 ) ; Minimum TTL $VAR1 = bless( { 'minimum' => 86400, 'serial' => 200701073, 'ttl' => 2711, 'mname' => 'disdns1.wa.gov', 'name' => 'wa.gov', 'rdata' => '<raw packet data>', 'retry' => 3600, 'refresh' => 10800, 'rdlength' => 43, 'type' => 'SOA', 'class' => 'IN', 'expire' => 604800, 'rname' => 'bruceh.dis.wa.gov' }, 'Net::DNS::RR::SOA' ); --
From: John W. Krahn on 17 Jan 2007 17:05
Paul Lalli wrote: > mmccaws2 wrote: >> >> open (NS_COMMAND, 'nslookup -type=soa wa.gov. ns1.six.net. |') >> or die "Ooops, $!"; > > This code is perfectly syntactically valid, but it's not the best. At > the very least, you should be using lexical filehandles, rather than > global barewords. That way, they're subject to strictures, two > independent pieces of code that use the same filehandle name can't > interphere with each other, and they're automatically closed when the > scope ends. > > open my $NS_COMMAND, 'nslookup -type=soa wa.gov. ns1.six.net. |') or > die "..."; > > These days, it's also preferred to use the three-argument form of open, > rather than specifying the mode within the filename (or program name, > in the case of open() for IPC) > > open my $NS_COMMAND, '-|', 'nslookup', '-type=soa wa.gov.', ^ That's not going to work with that space character in there. > 'ns1.six.net.' or die "..."; Either use a single string: open my $NS_COMMAND, '-|', 'nslookup -type=soa wa.gov. ns1.six.net.' or die "..."; Or a list with no whitespace: open my $NS_COMMAND, '-|', 'nslookup', '-type=soa', 'wa.gov.', 'ns1.six.net.' or die "..."; John -- Perl isn't a toolbox, but a small machine shop where you can special-order certain sorts of tools at low cost and in short order. -- Larry Wall |