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Illegal seek
Hello,
Sometimes I get the error message: "Illegal seek". An example of this
is when I have the following in a Perl script:
my $run = "touch abc";
`$run` || print STDERR "Command '$run' failed: $! \n";
The error message I get is:
Command 'touch abc' failed: Illegal seek
Yet, the file 'abc' is created/updated.
But when $run = "ls -las", I don't get this error message.
Does anyone know why I am getting this error? Is there a better way to
accomplish the same thing?
Eric
>>>>> "E" == Eric <ecarl @vmware.com> writes:
E> `$run` || print STDERR "Command '$run' failed: $! \n";
why are you using backticks when you don't want the output? the return
value of `` IS NOT an error message.
E> The error message I get is:
E> Command 'touch abc' failed: Illegal seek
you are likely getting some other error message left in $! as the
backticks always worked. any error touch makes would not be return in
the backticks but in $@.
E> Does anyone know why I am getting this error? Is there a better way to
E> accomplish the same thing?
perldoc -f utime
no reason to fork out as perl has it builtin.
uri
--
Uri Guttman ------ u@stemsystems.com -------- http://www.stemsystems.com
--Perl Consulting, Stem Development, Systems Architecture, Design and Coding-
Search or Offer Perl Jobs ---------------------------- http://jobs.perl.org
On Apr 13, 2:24 pm, Uri Guttman <u@stemsystems.com> wrote:
> >>>>> "E" == Eric <ecarl @vmware.com> writes: > E> my $run = "touch abc";
> E> `$run` || print STDERR "Command '$run' failed: $! \n";
> why are you using backticks when you don't want the output? the return
> value of `` IS NOT an error message.
> E> The error message I get is:
> E> Command 'touch abc' failed: Illegal seek
> you are likely getting some other error message left in $! as the
> backticks always worked. any error touch makes would not be return in
> the backticks but in $@.
> E> Does anyone know why I am getting this error? Is there a better way to
> E> accomplish the same thing?
> perldoc -f utime
> no reason to fork out as perl has it builtin.
> uri
> --
> Uri Guttman ------ u@stemsystems.com --------http://www.stemsystems.com
> --Perl Consulting, Stem Development, Systems Architecture, Design and Coding-
> Search or Offer Perl Jobs ---------------------------- http://jobs.perl.org
We do in fact want the response, at least when in verbose mode. For
clarity reasons, I didn't include all of the code.
As far as the 'touch' command goes, this is not the actual command we
are running. I changed it to this for simplicity reasons.
Having said this, I still am not clear on why I am getting the error
message with some commands but not others.
Eric
"Eric" <ecarl @vmware.com> writes: > On Apr 13, 2:24 pm, Uri Guttman <u @stemsystems.com> wrote: >> >>>>> "E" == Eric <ecarl @vmware.com> writes: >> E> my $run = "touch abc";
>> E> `$run` || print STDERR "Command '$run' failed: $! \n";
>> why are you using backticks when you don't want the output? the return
>> value of `` IS NOT an error message.
>> E> The error message I get is:
>> E> Command 'touch abc' failed: Illegal seek
>> you are likely getting some other error message left in $! as the
>> backticks always worked. any error touch makes would not be return in
>> the backticks but in $@.
> Having said this, I still am not clear on why I am getting the error
> message with some commands but not others.
value of `` is *supposed* to be undef. For those commands, you're printing
an error message because `` is undef, when in fact there was no error.
Other commands normally produce output, but print a message to STDERR on
failure, and nothing to STDOUT. For *those* commands, capturing nothing
with `` would indicate failure.
So like Uri said, the value returned by `` is not a reliable means of error
detection. You need to check $@ to detect errors with ``.
sherm--
--
Web Hosting by West Virginians, for West Virginians: http://wv-www.net
Cocoa programming in Perl: http://camelbones.sourceforge.net
On Apr 13, 3:31 pm, Sherm Pendley <spamt@dot-app.org> wrote:
> "Eric" <ecarl @vmware.com> writes: > > On Apr 13, 2:24 pm, Uri Guttman <u @stemsystems.com> wrote: > >> >>>>> "E" == Eric <ecarl @vmware.com> writes: > >> E> my $run = "touch abc";
> >> E> `$run` || print STDERR "Command '$run' failed: $! \n";
> >> why are you using backticks when you don't want the output? the return
> >> value of `` IS NOT an error message.
> >> E> The error message I get is:
> >> E> Command 'touch abc' failed: Illegal seek
> >> you are likely getting some other error message left in $! as the
> >> backticks always worked. any error touch makes would not be return in
> >> the backticks but in $@.
> > Having said this, I still am not clear on why I am getting the error
> > message with some commands but not others.
> For a command that produces no output when it succeeds, such as touch, the
> value of `` is *supposed* to be undef. For those commands, you're printing
> an error message because `` is undef, when in fact there was no error.
> Other commands normally produce output, but print a message to STDERR on
> failure, and nothing to STDOUT. For *those* commands, capturing nothing
> with `` would indicate failure.
> So like Uri said, the value returned by `` is not a reliable means of error
> detection. You need to check $@ to detect errors with ``.
> sherm--
> --
> Web Hosting by West Virginians, for West Virginians:http://wv-www.net
> Cocoa programming in Perl:http://camelbones.sourceforge.net- Hide quoted text -
>
Thank you both for your responses. I tried this, but got the same
error message.
Eric
Eric wrote: > Sometimes I get the error message: "Illegal seek". An example of this
> is when I have the following in a Perl script:
> my $run = "touch abc";
> `$run` || print STDERR "Command '$run' failed: $! \n";
> The error message I get is:
> Command 'touch abc' failed: Illegal seek
> Yet, the file 'abc' is created/updated.
> But when $run = "ls -las", I don't get this error message.
> Does anyone know why I am getting this error? Is there a better way to
> accomplish the same thing?
my @args = ( 'touch', 'abc' );
system( @run ) == 0 or print STDERR "Command '@run' failed: $? \n";
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
Uri Guttman wrote: >>>>>>"E" == Eric <ecarl @vmware.com> writes: > E> my $run = "touch abc";
> E> `$run` || print STDERR "Command '$run' failed: $! \n";
> why are you using backticks when you don't want the output? the return
> value of `` IS NOT an error message.
> E> The error message I get is:
> E> Command 'touch abc' failed: Illegal seek
> you are likely getting some other error message left in $! as the
> backticks always worked. any error touch makes would not be return in
> the backticks but in $@.
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
>>>>> "E" == Eric <ecarl @vmware.com> writes:
>>
>> So like Uri said, the value returned by `` is not a reliable means
>> of error detection. You need to check $@ to detect errors with ``.
E> Thank you both for your responses. I tried this, but got the same
E> error message.
and with what code? we can't debug /dev/null scripts. as for your
changing the command as it isn't touch, that is not fair to us either.
if you want help you first have to show some real code with a real
problem. touch isn't real and your use of backticks is very wrong as you
have shown it.
uri
--
Uri Guttman ------ u@stemsystems.com -------- http://www.stemsystems.com
--Perl Consulting, Stem Development, Systems Architecture, Design and Coding-
Search or Offer Perl Jobs ---------------------------- http://jobs.perl.org
>>>>> "JWK" == John W Krahn <some @example.com> writes:
>>>>>>> "E" == Eric <ecarl@vmware.com> writes:
>>
E> my $run = "touch abc";
E> `$run` || print STDERR "Command '$run' failed: $! \n";
>>
>> why are you using backticks when you don't want the output? the return
>> value of `` IS NOT an error message.
>>
E> The error message I get is:
>>
E> Command 'touch abc' failed: Illegal seek
>>
>> you are likely getting some other error message left in $! as the
>> backticks always worked. any error touch makes would not be return in
>> the backticks but in $@.
JWK> I think you mean $? instead of $@.
probably. i always confuse those and either rtfm or find other code
where i used the right one. :) in general i don't use backticks too
often anyway. i know what perl has builtin and i use backticks for
their output, not success/failure results.
uri
--
Uri Guttman ------ u@stemsystems.com -------- http://www.stemsystems.com
--Perl Consulting, Stem Development, Systems Architecture, Design and Coding-
Search or Offer Perl Jobs ---------------------------- http://jobs.perl.org
Eric schreef:
> For
> clarity reasons, I didn't include all of the code.
:(
--
Affijn, Ruud
"Gewoon is een tijger."
On Apr 14, 4:10 am, "Dr.Ruud" <rvtol+n@isolution.nl> wrote:
> Eric schreef: > > For
> > clarity reasons, I didn't include all of the code.
> :(
> --
> Affijn, Ruud
> "Gewoon is een tijger."
launch.pl file runs the mountDefaultBuild.pl script.
===========================================
File: launch.pl:
----------------
#! /usr/bin/perl -w
use strict;
my $script = "/usr/local/mountDefaultBuild.pl";
`$script` || print STDERR "Command '$script' failed: $?";
File: mountDefaultBuild.pl
--------------------------
#! /usr/bin/perl -w
use strict;
use Fcntl qw(:DEFAULT :flock);
my $execute = "/usr/sbin/exportfs -r";
my $umount = "umount /networkinstall/default";
my $mount = "mount -o loop /networkinstall/tmp/build.iso /
networkinstall/default";
unless (open SEMAPHORE, "> /tmp/mounts.lock") {
print STDOUT "unexpected problem opening /tmp/mounts.lock\n";
}
flock SEMAPHORE, Fcntl::LOCK_EX;
`$execute` || print STDERR "Command '$execute' failed: $?\n";
`$umount` || print STDERR "Command '$umount' failed: $?\n";
`$mount` || print STDERR "Command '$mount' failed: $?\n";
`$execute` || print STDERR "Command '$execute' failed: $?\n";
close SEMAPHORE;
===========================================
Thanks.
Eric
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