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Do you have a mnemonic or system? This has bothered me for years I always have to look it up

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closed as primarily opinion-based by terdon, Patrick, slm, Ramesh, vonbrand Jun 19 '14 at 17:12

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise.If this question can be reworded to fit the rules in the help center, please edit the question.

up vote 19 down vote accepted

If you are a C programmer, you can think of &1 as "the address of 1" so 2>&1 reads "redirect file descriptor #2 to the same place as #1".

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Don't know if it helps... Mnemonics are quite a personal stuff. – lgeorget Jun 19 '14 at 14:05
+12 That's also a correct description of what's happening. – Stéphane Chazelas Jun 19 '14 at 14:50
I wonder if it's how it was thought of ("the address of 1") when it was invented. As some people contributed heavily to both the C language and UNIX when they were invented, it's possible – lgeorget Jun 19 '14 at 15:03
I might start using this one instead ;) – goldilocks Jun 19 '14 at 15:39

"Two to and one" ("to" being >) makes more logical sense to me than "Two and to one", which is what I might usually confuse it with. If you consider "and one" as a single noun (a place), it also makes grammatical sense in context, which is harder to do with "Two and to one" -- you'd have to consider "to one" a single noun, and it still would not make contextual sense.

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I don't understand – Matt Jun 19 '14 at 22:40

Not a mnemonic, but I read it as follows:

0 is stdin. 1 is stdout. 2 is stderr. > is into. < is out of. & is file descriptor (in some shells).

2      >    &               1
stderr into file descriptor 1

redirect stderr into stdout

It might change if you have messed with any of the file descriptors prior to the redirection...

2>somefile 1>&2
2      >    somefile     1      >    &2
stderr into somefile and stdout into file descriptor 2

redirect stderr into somefile and stdout into somefile. 
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When you write 2>&1, you're saying "standard error goes to standard output".

Let's break that down.

First you want to memorize that standard error is 2 and standard output is 1.

So you've got 2 something something 1.

"goes to" is written >.

So you've got 2> something 1.

2>filename means send standard error to filename. But you don't want to send it to a file called 1. You want something else: the number of a file that's already open. That's what the & is for.

So 2>&1.

You can also think of it like you were doing an assignment, where the > is like an equals and the & is like a $, compare:


To understand a command line with multiple redirections, the important thing to know is that the redirections are done left to right. See Order of redirections for more details about that.

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I remembered that it is always 2 -> 1. Stderr to stdout.

The middle part is always the hard one and I always messed it up, until I remembered that first comes the sharp character >, then the character I can't write in real life &.

So never 2&>1, always 2>&1

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If you understand that FD2 is STDERR, you might think, "Oh, and capture STDERR where ever I send STDOUT (FD1)".

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My coworkers and I usually say "two is greater than one", because most of us don't always remember that stderr is file descriptor 2 and stdout is 1 (especially those new to unix/linux), so the other mnemonics about redirecting stderr don't really work. Only problem is, you still have to remember where the ampersand goes!

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