[7.3] umount says: "umount: /very/long/path (/dev/loop0) is unmounted" ?
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The greater-thans (>) in commands like these redirect the program’s output somewhere. In this case, something is being redirected into /dev/null, and something is being redirected into &1.
Standard in, out, and error
There are three standard sources of input and output for a program. Standard input usually comes from the keyboard if it’s an interactive program, or from another program if it’s processing the other program’s output. The program usually prints to standard output, and sometimes prints to standard error. These three file descriptors (you can think of them as “data pipes”) are often called STDIN, STDOUT, and STDERR.
Sometimes they’re not named, they’re numbered! The built-in numberings for them are 0, 1, and 2, in that order. By default, if you don’t name or number one explicitly, you’re talking about STDOUT.
Given that context, you can see the command above is redirecting standard output into /dev/null, which is a place you can dump anything you don’t want (often called the bit-bucket), then redirecting standard error into standard output (you have to put an & in front of the destination when you do this).
The greater-thans (>) in commands like these redirect the program’s output somewhere. In this case, something is being redirected into /dev/null, and something is being redirected into &1.
Standard in, out, and error
There are three standard sources of input and output for a program. Standard input usually comes from the keyboard if it’s an interactive program, or from another program if it’s processing the other program’s output. The program usually prints to standard output, and sometimes prints to standard error. These three file descriptors (you can think of them as “data pipes”) are often called STDIN, STDOUT, and STDERR.
Sometimes they’re not named, they’re numbered! The built-in numberings for them are 0, 1, and 2, in that order. By default, if you don’t name or number one explicitly, you’re talking about STDOUT.
Given that context, you can see the command above is redirecting standard output into /dev/null, which is a place you can dump anything you don’t want (often called the bit-bucket), then redirecting standard error into standard output (you have to put an & in front of the destination when you do this).
From what you are saying
Code:
{command} > /dev/null
is redirecting STDOUT to /dev/null, all I see is errors if there are any and if they are printed to STDERR.
And adding 2>&1 will redirect STDERR to STDOUT
Code:
{command} > /dev/null 2>&1
So, then I should se nothing?
if so, why am I getting this output when I'm redirecting to /dev/null?
Code:
umount: /very/long/path (/dev/loop0) is unmounted
Last edited by McZ; 03-15-2013 at 05:34 AM.
Reason: typo
Distribution: Void, Linux From Scratch, Slackware64
Posts: 3,152
Rep:
What is the exact command you are using? I can't reproduce this error, it may be a kernel error message for some reason some of which are not easy to redirect.
The form
Code:
SOMECOMMAND >/dev/null 2>&1
is correct although you can use a short cut in newer versions of bash like so
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