On 26 October 2017 at 21:59, Roberto C. Sánchez <robe...@debian.org> wrote: > On Thu, Oct 26, 2017 at 04:19:42PM +1100, David Margerison wrote: >> On 26 October 2017 at 12:23, Roberto C. Sánchez <robe...@debian.org> wrote: >> > >> > mountpoint -q $WorkingDirectory >> > if [[ $? = 0 ]] >> >> That will work, but is ridiculous considering this works by design: >> >> if mountpoint -q "$wd" ; then >> echo "$wd is a mountpoint" >> fi > > Yes, quite right. Though, my syntax makes it clear that what is being > tested/evlauated is the exit status, not the output. I know that the if > evaluates the exit status, but that may not be immediately evident to > someone who is not particularly familiar with shell programming.
That's a fair point, but the documentation of the 'if' statement in 'man bash' will make that immediately clear to anyone who cares to read it. The [[ test, the $? parameter, and the =0 test are three separate redundancies that are not needed here to achieve the desired result. So the code you gave is a good illustration of how $? works, but should also be identified as a bad example of how to correctly achieve the goal in this case. Because in shell syntax, the 'if' statement is conceived and intended to be used directly with any/all commands. So I believe that good guidance should make that point clearly, and that is my reason for writing again here, to present that alternative. Also, some shells do not support [[ and its syntax differs from [ and 'test' in various fun ways.
