1

When you are creating tutorials online for people to use in a single terminal sometimes it's nice to source inline code...however none of these worked as I would expect. I would expect foo to be "bar" for all of these. Anyone know why?

#!/usr/bin/env bash

source <(echo "export foo=bar");
echo "$foo"

source <(cat <<< "export foo=bar");
echo "$foo"

source <(cat <<EOF
  export foo=bar

EOF
);


echo "$foo"

My only guess is that source cannot read from a file descriptor? I also tried using . instead of source same thing.

I am on MacOS, bash --version output:

GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin18) 
Copyright (C) 2007 Free Software Foundation, Inc.
  • 1
    These all work in bash release 5.0.7(1). You should probably mention what actually happens when you run this, as well as what your bash version is. – Kusalananda May 30 at 17:04
  • Show your actual output. Also show your bash version: echo "$BASH_VERSION" – glenn jackman May 30 at 17:14
  • Why can't you just use eval? Yes, you can work around that bug with source /dev/fd/0 <<<'export foo=bar' (which will use a regular/seekable tempfile), but it's just as completely pointless as your examples. – mosvy May 30 at 17:59
  • Yeah eval might work - it's for copying commands to current terminal – Alexander Mills May 30 at 18:01
4

This would not work in bash releases before release 4.0 (for example, the default bash on macOS, which is release 3.2.57(1)).

Release 4.0 had a bugfix:

Fixed a bug that caused `.' to fail to read and execute commands from non- regular files such as devices or named pipes.

(that's from https://tiswww.case.edu/php/chet/bash/CHANGES)

The file read by source (or .) when you use it with a process substitution is not a regular file, so it would trigger the bug that was fixed in release 4.0.

The most recent release is currently release 5.0.7(1), where your code works as expected.

  • 1
    @Alexander, if you are on a mac, install bash via homebrew to get a more recent version. – glenn jackman May 30 at 17:17
  • Anybody know of a good way to easily switch between bash versions 3 4 and 5 on a machine? – Alexander Mills May 30 at 17:21
  • 1
    @AlexanderMills Clone the Git repository (git://git.savannah.gnu.org/bash.git) and check out the appropriate tag and build it? – Kusalananda May 30 at 18:56
  • thanks I used the technique here to build from gnu bash source: unix.stackexchange.com/questions/522023/… – Alexander Mills May 30 at 19:14

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