On 25/12/2014 15:32, Jilles Tjoelker wrote:
On Wed, Dec 24, 2014 at 12:33:32AM +0100, Vadim Zeitlin wrote:
On Wed, 24 Dec 2014 00:21:09 +0100 Harald van Dijk <harald@xxxxxxxxxxx> wrote:
HvD> On 23/12/2014 23:34, Vadim Zeitlin wrote:
HvD> > Hello,
HvD> >
HvD> > I'm not exactly sure if this is a bug because I didn't find any
HvD> > specification about how is this supposed to behave (to my surprise it
HvD> > turned out that $_ was not in POSIX), but please consider this:
HvD> >
HvD> > % zsh -c 'echo -n foo && echo $_'
HvD> > foofoo
HvD> > % bash -c 'echo -n foo && echo $_'
HvD> > foofoo
HvD> > % dash -c 'echo -n foo && echo $_'
HvD> > foo/usr/bin/dash
HvD>
HvD> This does come across as somewhat confusing, but $_ is really not a
HvD> special variable at all in dash.
Ah, this does explain it, thanks!
Dash does implement $_, but only in interactive mode.
Ah, apologies. In interactive mode, it indeed implements it, but
differently from bash. In dash, only commands that specify a command
name cause $_ to be set. For example,
dash -ic 'if a=b; then c=d; else e=f; fi; echo $_'
still prints
/usr/bin/dash
(or wherever dash is installed), because if statements, and variable
assignments, have no effect on $_. In bash, this prints a blank line,
because the prior value of $_ has not survived those variable assignments.
Cheers,
Harald van Dijk
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