Re: Unnecessary bash warning message

[Chet Ramey]

On 5/7/23 10:06 PM, Hyunho Cho wrote:

> Bash Version: 5.2
> Patch Level: 15
> Release Status: release
>
> #######################################################
>
>
> Process substitution can be used in place of a file in a command line
> as follows:
>
> bash$ cat test.jl
> for a in ARGS println(a) end
>
> bash$ julia test.jl 11 22 33
> 11
> 22
> 33
>
> bash$ julia <( cat <<\@
> for a in ARGS println(a) end
> @
> ) 11 22 33
> 11
> 22
> 33
>
> However, in the above method, the 11 22 33 arguments are placed at the
> end of the command line,
> which is not good for readability. So writing the following would make
> the command line much more readable,
> but it would output unnecessary warning messages.
>
> bash$ julia <( cat <<\@ ) 11 22 33
> for a in ARGS println(a) end
> @
> bash: warning: command substitution: 1 unterminated here-document
> 11
> 22
> 33

The process substitution is in its own parsing environment, from the `(' to
the `)', and the command must be contained within that parsing environment.
That includes any here-documents. Bash warns you that the here-document was
not terminated when the process substitution ends, and, trying to intuit
the true intent, goes ahead and collects here documents from the input
stream. It could be a syntax error, but bash just makes it a warning, so
you can change your code to do it the right way.

I see I might need to update the error message to specify it's process
substitution. Command and process substitution share the same parsing
functions and are identical from that perspective.

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/