5:38 a.m.
--
Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones
Read my programming blog: http://rwmj.wordpress.com
Fedora now supports 75 OCaml packages (the OPEN alternative to F#)
http://cocan.org/getting_started_with_ocaml_on_red_hat_and_fedora
6:18 a.m.
New subject: detecting write failure [Re: [PATCH] virt-cat: Remove some unused Perl module includes.
Richard W.M. Jones wrote:
Subject: [PATCH 3/4] virt-cat: Remove some unused Perl module
includes.
---
cat/virt-cat.pl | 3 ---
1 files changed, 0 insertions(+), 3 deletions(-)
diff --git a/cat/virt-cat.pl b/cat/virt-cat.pl
index 8db5348..748dbb8 100755
--- a/cat/virt-cat.pl
+++ b/cat/virt-cat.pl
@@ -25,9 +25,6 @@ use Sys::Guestfs::Lib qw(open_guest get_partitions
resolve_windows_path
inspect_operating_systems mount_operating_system);
use Pod::Usage;
use Getopt::Long;
-use Data::Dumper;
-use File::Temp qw/tempdir/;
-use XML::Writer;
use Locale::TextDomain 'libguestfs';
These look fine.
Unrelated to this particular change, you may want to
add these lines to virt-cat:
END { # use File::Coda; # http://meyering.net/code/Coda/
defined fileno STDOUT or return;
close STDOUT and return;
warn "$ME: failed to close standard output: $!\n";
$? ||= 1;
}
Otherwise, virt-cat could fail to detect/report write errors.
Try this:
virt-cat /some/file > /dev/full
It should fail.
This is a general problem in nearly every perl script
that writes to stdout.
6:28 a.m.
New subject: detecting write failure [Re: [PATCH] virt-cat: Remove some unused Perl module includes.
On Wed, Sep 23, 2009 at 01:18:06PM +0200, Jim Meyering wrote:
Unrelated to this particular change, you may want to
add these lines to virt-cat:
END { # use File::Coda; # http://meyering.net/code/Coda/
defined fileno STDOUT or return;
close STDOUT and return;
warn "$ME: failed to close standard output: $!\n";
$? ||= 1;
}
Otherwise, virt-cat could fail to detect/report write errors.
Try this:
virt-cat /some/file > /dev/full
It should fail.
It turns out that virt-cat does catch this error already, or more
precisely guestfs_download catches the error in the write to
/dev/stdout and does the right thing:
$ sudo ./cat/run-cat-locally /dev/vg_trick/F11x64 /boot/grub/grub.conf > /dev/full
download: /dev/stdout: write: No space left on device at
/home/rjones/d/libguestfs/cat/virt-cat.pl line 162.
$ echo $?
28
I'm not entirely sure where code 28 comes from.
However, this is a good suggestion in the general case and I'll have
to remember it for other perl scripts.
Rich.
--
Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones
Read my programming blog: http://rwmj.wordpress.com
Fedora now supports 75 OCaml packages (the OPEN alternative to F#)
http://cocan.org/getting_started_with_ocaml_on_red_hat_and_fedora
6:51 a.m.
New subject: detecting write failure [Re: [PATCH] virt-cat: Remove some unused Perl module includes.
Richard W.M. Jones wrote:
On Wed, Sep 23, 2009 at 01:18:06PM +0200, Jim Meyering wrote:
> Unrelated to this particular change, you may want to
> add these lines to virt-cat:
>
> END { # use File::Coda; # http://meyering.net/code/Coda/
> defined fileno STDOUT or return;
> close STDOUT and return;
> warn "$ME: failed to close standard output: $!\n";
> $? ||= 1;
> }
>
> Otherwise, virt-cat could fail to detect/report write errors.
>
> Try this:
>
> virt-cat /some/file > /dev/full
>
> It should fail.
It turns out that virt-cat does catch this error already, or more
precisely guestfs_download catches the error in the write to
/dev/stdout and does the right thing:
$ sudo ./cat/run-cat-locally /dev/vg_trick/F11x64 /boot/grub/grub.conf > /dev/full
download: /dev/stdout: write: No space left on device at
/home/rjones/d/libguestfs/cat/virt-cat.pl line 162.
$ echo $?
28
I'm not entirely sure where code 28 comes from.
Actually adding the above would help in *some* cases.
It's not as if --help and --version being robust is a big deal,
but try this:
$ ./virt-cat.pl --version > /dev/full && echo oops :
oops
$ ./virt-cat.pl --help > /dev/full
$
Note that that always exits with status of 1 (aka EXIT_FAILURE),
while the convention (at least for most GNU tools) is that PROG --help
exits with status 0, unless it fails, as above.
$ cat --help > /dev/full :
cat: write error: No space left on device
[Exit 1]
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Richard W.M. Jones