[Bug 1737846] Re: bash fails to redirect standard output of a pipeline to the input file of the fist pipeline's command

[Arbiel Perlacremaz]

Don't consider this as a bash bug. It's a misunderstanding by myself of
the pipeline operation.

Maybe a comment should be included in the reference manual to cleary
explain that the last command may try to open for writing the file still
open for reading by the first command, and that such a situation
obviously fails.

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https://bugs.launchpad.net/bugs/1737846

Title:
  bash fails to redirect standard output of a pipeline to the input file
  of the fist pipeline's command

Status in bash package in Ubuntu:
  New

Bug description:
  In a non-interactive bash session, redirecting the standard output to the file read by the pipeline's first command leads to random resuts : the redirection sometimes works, but generally the file is overwriten by an empty file.
  In an interactive session, the redirection works, which leads the user to look somewhere else to find a bug.

  However, when the last command is a user-writen function which
  simulates "cat", the resulting file is correct, as in an interactive
  session.

  Bash documentation does not prohibit such processing.

  Arbiel

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: bash 4.3-7ubuntu1.5
  ProcVersionSignature: Ubuntu 3.13.0-106.153-generic 3.13.11-ckt39
  Uname: Linux 3.13.0-106-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.23
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Tue Dec 12 23:51:22 2017
  InstallationDate: Installed on 2014-05-30 (1292 days ago)
  InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
  ProcEnviron:
   LANGUAGE=fr_FR
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=fr_FR.UTF-8
   SHELL=/bin/bash
  SourcePackage: bash
  UpgradeStatus: No upgrade log present (probably fresh install)

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