#752254 bash: Duplicating RO file descriptor for output is not a redirection error

Package:
bash
Source:
bash
Description:
GNU Bourne Again SHell
Submitter:
Igor Bogomazov
Date:
2014-06-21 17:36:06 UTC
Severity:
minor
#752254#5
Date:
2014-06-21 09:53:01 UTC
From:
To:
Dear Maintainer,

it is stated in manpage that duplicating RO file descriptor causes a
redirection error:

 >>>
$ man 1 bash | grep -A17 'Duplicating File Descriptors$' | tail -n2
       output (file descriptor 1) is used.  If the digits in word do not specify a  file  descriptor
       open  for  output,  a redirection error occurs.  If word evaluates to -, file descriptor n is
 <<<

but it does not:

 >>>
$ ( set -e ; exec 3< /dev/null ; exec 4>&3 ; echo OK )
OK
 <<<

an error would be to write to the RO file descriptor:

 >>>
$ ( set -e ; exec 3< /dev/null ; exec 4>&3 ; echo >&4 ; echo OK )
bash: echo: write error: Bad file descriptor
 <<<

it is not a redirection error, but another one; I have checked two other
shells: dash and ksh, — neither of them raises any redirection error, then I
guess it is a documentation bug, and this sentence can be safely removed:

 >>>
If the digits in word do not specify a file descriptor open for output, a redirection error occurs.
 <<<