Mailinglist Archive: opensuse (3232 mails)
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Re: [SLE] mkisofs question
- From: stephan beal <stephan@xxxxxxxx>
- Date: Thu, 10 Aug 2006 19:37:44 +0000 (UTC)
- Message-id: <200608102136.39340.stephan@xxxxxxxx>
On Thursday 10 August 2006 01:53, Carl William Spitzer IV wrote:
> Oops forgot the example:
>
> #!/bin/bash
> mount /dev/hda1 /windows/c/
> vDate=`date +20%y-%m-%d`
> tar -zcvf Cdrive$vDate.tar.gz /windows/c
> echo $vDate
> umount windows/c/
An optimization note:
Leave off the 'v' (verbose) option to tar to speed up your tar times.
Input/Output (in this case output to the console) is one of the slowest
things a computer can be forced to do. As an example of how this simple
flag can speed things up, try the following in a console expanded to
fill up your whole desktop:
cd /
find .
Now shrink that console down to, say 1/4 the size of your screen and do
it again:
cd /
find .
It will run a lot faster the second time because of the way output and
updating of the console window works. (It will also run faster because
the OS cached many of the file entries during the first run, but even
without that caching it will run faster in a smaller window.)
Now try:
cd /
find . > /dev/null
and you'll see that it runs a lot faster because output to /dev/null is
a lot faster than output to a console. The exact reasons for this are
detailed and technical, but essentially it's because the console window
has to update it's whole visible area when it outputs a new line to the
screen and the program which generates the output has to wait on the
console to do that. The amount of time is trivial for most purposes but
can indeed be non-trivial when running an app which generates a lot of
output to "standard out" (the console, unless you redirect the output
as we did in the last example).
The moral of the story is: don't use the 'v' flag to tar unless you
really need it, especially when doing a large tar (such as /windows/C).
PS: and use date +%Y for a 4-year date instead of date +20%y, which
isn't Y2100 compliant.
:)
--
----- stephan@xxxxxxxx http://s11n.net
"...pleasure is a grace and is not obedient to the commands
of the will." -- Alan W. Watts
> Oops forgot the example:
>
> #!/bin/bash
> mount /dev/hda1 /windows/c/
> vDate=`date +20%y-%m-%d`
> tar -zcvf Cdrive$vDate.tar.gz /windows/c
> echo $vDate
> umount windows/c/
An optimization note:
Leave off the 'v' (verbose) option to tar to speed up your tar times.
Input/Output (in this case output to the console) is one of the slowest
things a computer can be forced to do. As an example of how this simple
flag can speed things up, try the following in a console expanded to
fill up your whole desktop:
cd /
find .
Now shrink that console down to, say 1/4 the size of your screen and do
it again:
cd /
find .
It will run a lot faster the second time because of the way output and
updating of the console window works. (It will also run faster because
the OS cached many of the file entries during the first run, but even
without that caching it will run faster in a smaller window.)
Now try:
cd /
find . > /dev/null
and you'll see that it runs a lot faster because output to /dev/null is
a lot faster than output to a console. The exact reasons for this are
detailed and technical, but essentially it's because the console window
has to update it's whole visible area when it outputs a new line to the
screen and the program which generates the output has to wait on the
console to do that. The amount of time is trivial for most purposes but
can indeed be non-trivial when running an app which generates a lot of
output to "standard out" (the console, unless you redirect the output
as we did in the last example).
The moral of the story is: don't use the 'v' flag to tar unless you
really need it, especially when doing a large tar (such as /windows/C).
PS: and use date +%Y for a 4-year date instead of date +20%y, which
isn't Y2100 compliant.
:)
--
----- stephan@xxxxxxxx http://s11n.net
"...pleasure is a grace and is not obedient to the commands
of the will." -- Alan W. Watts
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