> And what if someone is running on a (perhaps old) Linux distro that does not > have python3 installed by default?
The idea would be to find both but prefer python3, but that’s infeasible inside configure without a separate pre-configure configure to write “configure.py" or virtual-env. > for pyimpls in python3 python2 python /usr/bin/python /usr/bin/env python ; do > command -v > /dev/null $pyimpls && exec $pyimpls $0 "$@“ > And there you have, you are trying to check for '/usr/bin/env python', but > the shell code you wrote will not work the way you are expecting. > Also, unless you are running on a funny environment that does not have > /usr/bin/ in $PATH, the trial for 'python' should be enough, and the > /usr/bin/python /usr/bin/env python look redundant. Am I missing something? This line checks if pyimpls exists in order, and then runs pyimpls ./configure so if any of the previous pyimpls exist then it doesn’t check the rest. The last “ should be a regular quotation mark. If it finds a working python it runs configure once then exits, instead of continuing through the rest of the list. > "Echo" ? Are you really running this on Ubuntu? Auto-correct strikes again :(. It is “echo” in my script. > BTW, Are you aware of the behavior of `command -v` with shell aliases? No, this is a good point you bring up. I tried using the option -p from the manpage but that also doesn’t seem to skip aliases. Not sure how this can be addressed, seems like escaping pyimpls using \ or ‘ or “ doesn’t fix this either... > -p use a default value for PATH that is guaranteed to find all of > the standard utilities To be clear I’m not saying my script is a change petsc should adopt, hence no MR. It is a hack and a half, and likely doesn’t work on some of the other shells as well as a whole host of portability problems. It's more-so to foster discussion, and see if anyone else has a cleaner automatic form. Best regards, Jacob Faibussowitsch (Jacob Fai - booss - oh - vitch) Cell: (312) 694-3391 > On Apr 17, 2020, at 4:21 PM, Lisandro Dalcin <dalc...@gmail.com> wrote: > > > > On Fri, 17 Apr 2020 at 20:41, Jacob Faibussowitsch <jacob....@gmail.com > <mailto:jacob....@gmail.com>> wrote: > Hello All, > > I use an Ubuntu docker image based on jedbrown/mpich-ccache and ran into the > following error (Dockerfile attached as well). > > If in a user only has python3 installed and not python2 then /usr/bin/python > doesn’t exist. > > And what if someone is running on a (perhaps old) Linux distro that does not > have python3 installed by default? > > Given that python2 has gone the way of the dodo perhaps petsc should be > looking for python3 over python2. This is a somewhat funky but functioning > implementation that replaces the shebang line in configure that I have been > using to default to python3. I don’t know how portable it is however, I > believe “command" is not universally available in every shell? > #!/bin/sh > # “”” is comment in python, and : is noop in shell so this configure can be > run as ./configure and python2.7 ./configure > """:" > > This kind of trickery may be fragile... > > # Find the right python implementation, check by sending it on over to dave > for pyimpls in python3 python2 python /usr/bin/python /usr/bin/env python ; do > > And there you have, you are trying to check for '/usr/bin/env python', but > the shell code you wrote will not work the way you are expecting. > Also, unless you are running on a funny environment that does not have > /usr/bin/ in $PATH, the trial for 'python' should be enough, and the > /usr/bin/python /usr/bin/env python look redundant. Am I missing something? > > command -v > /dev/null $pyimpls && exec $pyimpls $0 "$@“ > > And the last quote the line above is likely wrong, it is an unicode character. > > done > # Error code in case things go awry > Echo “PYTHON NOT FOUND” >2 > > "Echo" ? Are you really running this on Ubuntu? > Or you just hacked in on macOS and assumed that it will work everywhere? > > BTW, Are you aware of the behavior of `command -v` with shell aliases? > > $ alias python=python3 > $ command -v python > alias python='python3' > > > -- > Lisandro Dalcin > ============ > Research Scientist > Extreme Computing Research Center (ECRC) > King Abdullah University of Science and Technology (KAUST) > http://ecrc.kaust.edu.sa/ <http://ecrc.kaust.edu.sa/>