suppressing an error message using the "ls" command

basher400 · 03-30-2005, 01:35 AM

hi

Is there a way to suppress the "No such file or directory" error message when using the "ls" command ?

thanks

zeropash · 03-30-2005, 01:56 AM

2> /dev/null
can redirect the error messages to /dev/null or use some other file if you are interested in the error messages.
for ex
ls asdf 2> /dev/null

basher400 · 03-30-2005, 02:01 AM

Quote:

Originally posted by zeropash
2> /dev/null
can redirect the error messages to /dev/null or use some other file if you are interested in the error messages.
for ex
ls asdf 2> /dev/null

thanks.

can I redirect it to null or to nothing, instead to a file?
something like:
ls nofilehere > null
(of course this create a "null" file with the output and I still get the output to my screen)

I don't want any output at all

gbonvehi · 03-30-2005, 02:21 AM

ls nofilehere &> /dev/null
ls nofilehere >& /dev/null

basher400 · 03-30-2005, 02:42 AM

Quote:

Originally posted by gbonvehi
ls nofilehere &> /dev/null
ls nofilehere >& /dev/null

"ls nofilehere >& /dev/null" works on getting no print to the screen - that's progress

but the output still goes to "/dev/null" which I want to prevent

oneandoneis2 · 03-30-2005, 02:51 AM

I think the only ways to do that are:

- Re-write the ls source code to not generate errors.

- Don't look for files that aren't there

keefaz · 03-30-2005, 03:23 AM

Try to be clear as I don't get what you want

- output the error to a file ?
- output the error to nothing ?

basher400 · 03-30-2005, 03:53 AM

Quote:

Originally posted by keefaz
Try to be clear as I don't get what you want

- output the error to a file ?
- output the error to nothing ?

sorry.
I want to output to nothing.

I just realized "/dev/null" is not an actual file - I mistakenly concluded that from the syntax of it (am I right?)

everything I output to "/dev/null" is actually outputted to nothing? I didn't know that - if so that's the answer I'm looking for.

scuzzman · 03-30-2005, 04:01 AM

/dev/null is the *NIX black hole - anything that goes there doesn't come out.

keefaz · 03-30-2005, 04:04 AM

You understand it right, "everything I output to /dev/null is actually outputted to nothing"

from: man 4 null

Quote:

Data written on a null or zero special file is discarded.

runlevel0 · 04-02-2005, 09:01 AM

Quote:

Originally posted by basher400
thanks.

can I redirect it to null or to nothing, instead to a file?
something like:
ls nofilehere > null
(of course this create a "null" file with the output and I still get the output to my screen)

I don't want any output at all

Code:

runlevel0@soviet ~/tmp $ ls comaro 2> /dev/null            (first attempt, no output)
runlevel0@soviet ~/tmp $ ls comaro                                         (w/o redirecting)
ls: comaro: No such file or directory                                           (STDERR output)

/dev/null is no a file at all !!

It's the Original Unix Black Hole((TM), a device which has no actual device attached.
It's a device leading to the Unknown Dimension. Note that the /dev filesystem hosts device nodes, not files. You can see this with the file command:

Code:

file /dev/null
/dev/null: character special (1/3)

while for a text file: 

file /etc/hosts
/etc/hosts: ASCII English text

The '2>' part of the command says that the STDERR (the standard error output) should be written to /dev/null (2 stands for STDERR and the '>' sign is a redirector).

Keeping it simple: ls -l 2> /dev/null sends the error outpout to a void device which is writable.

Another trick you can do with /dev/null is 'nulling' or voiding a file, writing the content of /dev/null (nothing) to that file:

Code:

#! /bin/sh
# void.sh
# simple script to set a text file to 0 bits
# invoque it with: void FILENAME

cat /dev/null > $1

Save this as void.sh and invoke it whith: ./void.sh or place it in your $PATH, or even better add
this to your ~/.bashrc:

Code:

void ()  { cat /dev/null > $1 ; }

jlliagre · 04-02-2005, 11:08 AM

Quote:

void () { cat /dev/null > $1 ; }

As "catenating" /dev/null is kind of no op, this shell function can be simplified and optimized to:

Code:

void ()  { > $1 ; }