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by maxeda 107 days ago
> I am thinking that they are using & like it is used in c style programming languages. As a pointer address-of operator. [...] 2>&1 would represent 'direct file 2 to the address of file 1'.

I had never made the connection of the & symbol in this context. I think I never really understood the operation before, treating it just as a magic incantation but reading this just made it click for me.
1 comments
jibal 107 days ago
No, the shell author needed some way to distinguish file descriptor 1 from a file named "1" (note that 2>1 means to write stderr to the file named "1"), and '&' was one of the few available characters. It's not the address of anything.

To be consistent, it would be &2>&1, but that makes it more verbose than necessary and actually means something else -- the first & means that the command before it runs asynchronously.

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kazinator 107 days ago
It's not inconsistent. The & is attached to the redirection operator, not to the 1 token. The file descriptor being redirected is also attached:

Thus you cannot write:

  2 > &1
You also cannot write

  2 >& 1
However you may write

  2>& 1
The n>& is one clump.
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