[Toybox] Would someone please explain what bash is doing here?

[Chet Ramey]

On 5/2/20 4:01 PM, Rob Landley wrote:

> Why does  the export flag on $_ toggle?

It does three different things. It's initially exported if bash inherits it
from the environment at startup; after that it does its thing.

"_      At shell startup, set to the absolute pathname  used  to  invoke
        the  shell or shell script being executed as passed in the envi-
        ronment or argument list.  Subsequently, expands to the last ar-
        gument  to  the  previous  simple  command executed in the fore-
        ground, after expansion.  Also set to the full pathname used  to
        invoke  each  command executed and placed in the environment ex-
        ported to that command.   When  checking  mail,  this  parameter
        holds the name of the mail file currently being checked."

We picked that up from ksh.


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