On Wed, 4 Oct 2017, Eduardo A. Bustamante López wrote:
> On Tue, Oct 03, 2017 at 10:29:08PM +0200, Mikulas Patocka wrote: > > If $OLDPWD points to a non-existing directory, 'cd -' will fail. > > But if we clear $OLDPWD, 'cd -' will fail too (with just different message). > [...] > > I performed the following tests: > > > dualbus@ubuntu:~$ for sh in mksh ksh93 dash zsh posh bash; do echo $sh \| > $(OLDPWD=/invalid $sh -c 'echo "$OLDPWD | "; cd -; echo " | $?"' 2>&1); done > mksh | /invalid | mksh: cd: /invalid: No such file or directory | 2 > ksh93 | /invalid | ksh93: cd: /invalid: [No such file or directory] | 1 > dash | /invalid | dash: 1: cd: can't cd to /invalid | 2 > zsh | /home/dualbus | | 0 > posh | /invalid | posh: cd: /invalid - No such file or directory | 1 > bash | | bash: line 0: cd: OLDPWD not set | 1 > > dualbus@ubuntu:~$ for sh in mksh ksh93 dash zsh posh bash; do echo $sh \| > $(OLDPWD=/tmp $sh -c 'echo "$OLDPWD | "; cd -; echo " | $?"' 2>&1); done > mksh | /tmp | /tmp | 0 > ksh93 | /tmp | /tmp | 0 > dash | /tmp | /tmp | 0 > zsh | /home/dualbus | | 0 > posh | /tmp | /tmp | 0 > bash | /tmp | /tmp | 0 > > > So: > > - Bash is the only major shell that performs stat() on OLDPWD to see if it's > going to import it from the environment or initialize it to an empty > value. > > - Zsh doesn't import OLDPWD from the environment (bash's old behavior) > > - The rest of the shells (mksh, ATT ksh, dash, posh) import OLDPWD from > the environment unconditionally. > > - Mikulas already made the argument above of why this change wouldn't > break existing scripts that rely on bash performing the stat(). > > - I don't see a way around this behavior using existing bash features. > The value of OLDPWD can't be reset via BASH_ENV or other > initialization mechanisms. Sure, `unset OLDPWD; program' might work, > but I wouldn't call that a solution. > > > Given the above, I've changed my mind, and I think this patch should be > fine :-) Hi Will you commit my patch? - if you agree with it. Mikulas
