can someone please inform me how this works

> filename.txt

this emptys the file but i cant find what > is doing, what is >*
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On 08/11/2011 01:18 PM, nathan nolast wrote:

can someone please inform me how this works

> filename.txt

this emptys the file but i cant find what > is doing, what is >


http://www.simplehelp.net/2009/04/08/how-to-save-the-output-of-a-linux-command-to-a-file/


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On 08/10/2011 10:18 PM, nathan nolast wrote:

can someone please inform me how this works

> filename.txt

this emptys the file but i cant find what > is doing, what is >


the > symbol puts the output of the command into the file. So try this

$echo "here is some text to try out"

Then try this:

$echo "here is some text to try out" > testfile.txt

Examine the file. Now try two more things:

$echo "this text should replace what was in the file" > testfile.txt

$echo "this text should NOT replace what was in the file before" >>
testfile.txt


Enjoy

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On Wed, August 10, 2011 10:18 pm, nathan nolast wrote:
> can someone please inform me how this works
>> filename.txt
> this emptys the file but i cant find what > is doing, what is >

It's called stdio redirection or some (well actually a lot of) people just
call it I/O redirection. You can redirect stdin and you can redirect. <<
< stdin stdout > >>, the proper way to truncate a file is actually ">
file.txt" or ":> file.txt" and nothing more, no echo, with an echo of any
kind you always end up with at least 1 byte written to the file which
defeats the purpose of what you are trying to do if you want to down and
dirty about it.

http://tldp.org/LDP/abs/html/io-redirection.html


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nice, all great answers
i appreciate it.


On Thu, Aug 11, 2011 at 2:18 AM, Jordon Bedwell <jordon@envygeeks.com> wrote:


On Wed, August 10, 2011 10:18 pm, nathan nolast wrote:

> can someone please inform me how this works

>> filename.txt

> this emptys the file but i cant find what > is doing, what is >



It's called stdio redirection or some (well actually a lot of) people just

call it I/O redirection. *You can redirect stdin and you can redirect. *<<

< stdin stdout > >>, the proper way to truncate a file is actually ">

file.txt" or ":> file.txt" and nothing more, no echo, with an echo of any

kind you always end up with at least 1 byte written to the file which

defeats the purpose of what you are trying to do if you want to down and

dirty about it.



http://tldp.org/LDP/abs/html/io-redirection.html





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so, is it possible to redirect the output of a file?

touch ioredirect.txt
echo "this is a test" > ioredirect.txt
vim.tiny ioredirect.txt** -- looks good
echo < ioredirect.txt

?


On Thu, Aug 11, 2011 at 10:53 AM, nathan nolast <nathan1465@gmail.com> wrote:

nice, all great answers
i appreciate it.


On Thu, Aug 11, 2011 at 2:18 AM, Jordon Bedwell <jordon@envygeeks.com> wrote:



On Wed, August 10, 2011 10:18 pm, nathan nolast wrote:

> can someone please inform me how this works

>> filename.txt

> this emptys the file but i cant find what > is doing, what is >



It's called stdio redirection or some (well actually a lot of) people just

call it I/O redirection. *You can redirect stdin and you can redirect. *<<

< stdin stdout > >>, the proper way to truncate a file is actually ">

file.txt" or ":> file.txt" and nothing more, no echo, with an echo of any

kind you always end up with at least 1 byte written to the file which

defeats the purpose of what you are trying to do if you want to down and

dirty about it.



http://tldp.org/LDP/abs/html/io-redirection.html





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On Thu, 2011-08-11 at 11:03 -0400, nathan nolast wrote:
> so, is it possible to redirect the output of a file?
>
> touch ioredirect.txt
> echo "this is a test" > ioredirect.txt
> vim.tiny ioredirect.txt -- looks good
> echo < ioredirect.txt
>
> ?

cat < ioderict.txt

Note also the use of a pipe '|' for "piping" the standard output of one
command into another command's standard input.

e.g. something I do regularly, encrypt and decrypt a collection of
files:
tar cf - directory | gpg -c > directory.tar.gpg
gpg -d directory.tar.gpg | tar xf -

Or e.g. split the tar archive into 100MB chunks.
- tells tar to write to stdout, and split to read from stdin.
gpg reads and writes to stdout here by default.
tar cf - dir | gpg -c | split -b100m -d - dir.tar.gpg.

And decrypt:
cat dir.* | gpg -d | tar xf -

And so forth.

Tero



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it would redirect the null input into the file.


From: nathan nolast <nathan1465@gmail.com>
To: ubuntu-users@lists.ubuntu.com
Sent: Thursday, August 11, 2011 12:18 AM
Subject: Command help

can someone please inform me how this works

>
filename.txt

this emptys the file but i cant find what > is doing, what is >*
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nathan1465@gmail.com


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On Thu, 2011-08-11 at 11:03 -0400, nathan nolast wrote:
> so, is it possible to redirect the output of a file?
>

Please don't top post

> This message contains confidential information and is intended only
> for the individual named. If you are not the named addressee you
> should not disseminate, distribute or copy this e-mail. Please notify
> the sender immediately by e-mail if you have received this e-mail by
> mistake and delete this e-mail from your system.

That is just annoying and doesn't mean squat legally. Ric


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On Thu, 2011-08-11 at 17:01 -0400, Ric Moore wrote:
> On Thu, 2011-08-11 at 11:03 -0400, nathan nolast wrote:
> > so, is it possible to redirect the output of a file?
> >
>
> Please don't top post
>
> > This message contains confidential information and is intended only
> > for the individual named. If you are not the named addressee you
> > should not disseminate, distribute or copy this e-mail. Please notify
> > the sender immediately by e-mail if you have received this e-mail by
> > mistake and delete this e-mail from your system.
>
> That is just annoying and doesn't mean squat legally. Ric
>
>
> --
> My father, Victor Moore (Vic) used to say:
> "There are two Great Sins in the world...
> ..the Sin of Ignorance, and the Sin of Stupidity.
> Only the former may be overcome." R.I.P. Dad.
> Linux user# 44256
>
>

+1


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