Category Archives: English

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After the upgrade to Linux kernel 2.6.38, the boot process for my machine hang quite long while Populating /dev with existing devices through uevents. After investigations it turns out that the cx88 driver used for my Hauppauge WinTV HVR-1300 tv card was not correctly converted to the new mutex system while removing the BKL. This is being tracked in the kernel bugzilla as bug #31962.

Fortunately, there is a patch attached to the mentioned bug report which resolves the problem:

cd /usr/src/linux
wget -O cx88-2.6.38-fix-driver-deadlocks.patch 'https://bugzilla.kernel.org/attachment.cgi?id=53722'
patch -p1 < cx88-2.6.38-fix-driver-deadlocks.patch

[Edited on 2011-04-23: replaced patch 52902 with 53722]

After applying the patch, build and install your kernel as usual. But there are still some more problems with 2.6.38 related to tvtime. See also my next post.

I do not follow kernel development close enough to know in which git tree this has to show up to confirm if it has been merged yet. Hopefully this patch will make it into the next kernel release.

bash: reuse last argument from previous command

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Reuse the last argument of the previous command with !$:

$ echo abc def
abc def
$ echo !$
def

A common use case would be mkdir and cd:

$ mkdir foo
$ cd !$

You can also insert the last argument of the previous command and continue typing with <ESC>.:

$ echo abc def
abc def
$ echo <ESC>. ghi
def ghi

Oh, the little things… 🙂

bash: for-loop with glob patterns

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It is common to use a for-loop with glob patterns:

for i in *.txt; do
    mv $i $i.old
done

But if the glob pattern does not match anything it will be preserved unchanged in the command. This results in command execution of mv *.txt *.txt.old which fails because no file named *.txt (literally!) exists.

As this is not the desired behavior, here is a way how to do this as expected without forking using the nullglob bash shell option.

oldnullglob=$(shopt -p nullglob)
shopt -s nullglob

for i in *.txt; do
    mv $i $i.old
done

eval "$oldnullglob" 2>/dev/null
unset oldnullglob

This will silently prevent the execution of the mv command. If you use failglob instead of nullglob bash will interrupt the evaluation of any command if the glob pattern did not match anything.

Disclaimer: Be careful with this option, as this will not be the expected behavior in all cases. Most (in)famously it breaks bash-completion if you set it in your interactive bash session. I suggest to use it temporary only.