Very Computer

by **Rea** » Sat, 15 May 1999 04:00:00

Hello everybody,

I'm looking for a way to redirect output to a file OR stdout using a
variable. Imagine something like the following command :

tar -xf some-software.tar >> ${LOGFILE_NAME}

There are 3 possible values for LOGFILE_NAME :
1. a filename : for logging to a file
2. the null-device : for ignoring all output
3. standard output : for 'normal' display

Option 1 and 2 are respectively a filename and /dev/null - both are true
for all Unix flavors. What can I use for the 3rd option ?

I'm usually on a Digital Unix system, where theoretically /dev/fd/1
should work but this device doesn't exist by default (see "man fd"). Nor
can I use redirection ( > ) character in a variable.

Anybody any great ideas ? Thank very much in advance.

Cheers,
Real
--

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by **Alex Baril** » Sat, 15 May 1999 04:00:00

> Hello everybody,

> I'm looking for a way to redirect output to a file OR stdout using a
> variable. Imagine something like the following command :

> tar -xf some-software.tar >> ${LOGFILE_NAME}

> There are 3 possible values for LOGFILE_NAME :
> 1. a filename : for logging to a file
> 2. the null-device : for ignoring all output
> 3. standard output : for 'normal' display

> for all Unix flavors. What can I use for the 3rd option ?

echo "this will be printed on your current tty" > `tty`

Mind backticks around tty command.

Cheers,
Alex.
--
Before the accident, I even could not spell UNIX

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by **Sriranga Veeraraghava** » Sat, 15 May 1999 04:00:00

> There are 3 possible values for LOGFILE_NAME :
> 1. a filename : for logging to a file
> 2. the null-device : for ignoring all output
> 3. standard output : for 'normal' display

> Option 1 and 2 are respectively a filename and /dev/null - both are true
> for all Unix flavors. What can I use for the 3rd option ?

For case 3 try something like:

LOGFILE_NAME=`tty`

This should work on most unicies (works on Solaris/Linux). Normally
tty is located in /usr/bin/tty, but it might also be /bin/tty.

by **Eric Amic** » Sat, 15 May 1999 04:00:00

> Hello everybody,
> I'm looking for a way to redirect output to a file OR stdout using a
> variable. Imagine something like the following command :
> tar -xf some-software.tar >> ${LOGFILE_NAME}
> There are 3 possible values for LOGFILE_NAME :
> 1. a filename : for logging to a file
> 2. the null-device : for ignoring all output
> 3. standard output : for 'normal' display
> Option 1 and 2 are respectively a filename and /dev/null - both are true
> for all Unix flavors. What can I use for the 3rd option ?

Assuming "normal display" means sending it to the screen and not to
standard output, use /dev/tty.

--
Eric Amick
Columbia, MD

Very Computer

HowTo: logging to file or stdout

HowTo: logging to file or stdout

HowTo: logging to file or stdout

HowTo: logging to file or stdout

HowTo: logging to file or stdout