[TUHS] redirection wildness in v7
Ralph Corderoy
ralph at inputplus.co.uk
Fri Nov 10 01:04:56 AEST 2017
Hi Will,
> Why does the first of these incantations not present text, but the
> second does (word is a file)? Neither errors out.
>
> $ <word | sed 20q
> $ <word sed 20q
That's still the case with modern-day sh(1).
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_09_01
explains that a simple command doesn't need to result in a command name
to execute. In your first pipeline, there's nothing to copy the data
from the first subshell's stdin redirected from ./word to the subshell's
stdout that's pipes into sed's stdin. Adding a command to do the copy
works.
<word cat | sed 20q
--
Cheers, Ralph.
https://plus.google.com/+RalphCorderoy
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