On 7/5/24 4:38 PM, Emanuele Torre wrote:
More funny things have been discovered since.It has been brought up when discussing this in the #bash IRC channel of irc.libera.chat, that if you run eval '<file' in $(), the contents of file are output to stdout, in every version of bash since it was introduced.
This is a consequence of using the same code for a number of things: the same function handles command substitution, process substitution, running traps, eval, mapfile, source, fc, and other things (basically any time you take a string and evaluate it); there isn't enough detection of the specific case of command substitution we're talking about here.
So you can for example use this to concatenate two files in pure bash; like $(cat <f; cat <g):
Yeah, this is clearly not the intent of the feature, but more an accident of the implementation and the different uses of this function leaking into each other.
I have also noticed that if you source a file from $() and the last logical line of that file contains only a simple command with only one read-only stdin redirection, bash will also print out that file, again, in all versions of bash with $(<):
I'm not sure how this can be considered anything but a bug, no matter how
long it's existed.
The best thing to do is probably to remove this (legacy) code from that
common function; with the re-implmentation of command substitution parsing
in bash-5.2, the documented usage doesn't go through that code path any
more.
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU c...@case.edu http://tiswww.cwru.edu/~chet/
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