building shipshape without realpath fails "silently" about shipshape HOT 3 CLOSED

@zrlk @schroederc
This code comes from https://github.com/google/kythe/blame/master/setup_bazel.sh originally.

I notice that we always call realpath -s and we furnish the following workaround for MacOS:

realpath() {
    python -c 'import os, sys; print os.path.realpath(sys.argv[2])' $@
}

But realpath -s and os.path.realpath() don't do the same thing! E.g.,

$ realpath -s bazel-bin/../foo
/home/clconway/git/shipshape/foo
$ python -c 'import os, sys; print os.path.realpath(sys.argv[2])' -s bazel-bin/../foo
/home/clconway/.cache/bazel/_bazel_clconway/221df40891e1938542beb77d30927c8e/shipshape/bazel-out/local_linux-fastbuild/foo

I think we can easily add the workaround for non-Mac systems, but I wonder which behavior is correct?

from shipshape.

BTW I agree that readlink is probably preferable to realpath, but readlink -e also doesn't match the behavior of realpath -s.

from shipshape.

Indeed they are not interchangable with those flags.

Another simple way to improve the way it currently works without breaking anything is to check for realpath before first usage and give a better error message if it does not exist. Thought it might be better to only use readlink.

Something like this below, adapted from SO:

#!/bin/bash
command -v realpath >/dev/null 2>&1 || { echo >&2 "I require realpath but it's not installed.  Aborting."; exit 1; }

I tried it on my ubuntu and it worked like intended when removing and reinstalling realpath.

from shipshape.