On Wed, Jul 8, 2020 at 2:44 AM 'Jacob Kopczynski' via golang-nuts <
golang-nuts@googlegroups.com> wrote:
> I tried to state a path relative to the home directory, since in the
> context I am writing for the path from ~ to the Git repository will be
> consistent, though the meaning of ~ may change based on user. A snippet:
>
> const specPath = "~/trunk/infra/metadata/config.cfg"
> absPath, _ := filepath.Abs(specPath)
> if err := readJSONPb(absPath, &s); err != nil {
> fmt.Printf("specPath is %s, or as absolute %s\n", specPath, absPath)
> return nil, errors.Annotate(err, "extracting tests from spec").Err()
> }
> However, this produces this output:
> specPath is ~/trunk/infra/metadata/config.cfg, or as absolute
> /home/jkop/trunk/infra/~/trunk/infra/metadata/config.cfg
> extracting tests from spec: read JSON pb: open
> /home/jkop/trunk/infra/~/trunk/infra/metadata/config.cfg: no such file or
> directory
>
> This is a) surprising, since I would expect a platform-sensitive absolute
> path function to deal with platform-global shortcuts like ~, and
>
~ is not a "platform global shortcut". It's an expansion a shell (bash,
zsh, etc) does for convenience.
open() and similar C-level (or Go level etc) function are not opening files
through a shell.
> b) completely undocumented. The docs say that "Abs returns an absolute
> representation of path. If the path is not absolute it will be joined with
> the current working directory to turn it into an absolute path." It doesn't
> say "If the path is not *rooted*", but "not *absolute*". This is not an
> absolute *representation* but it does specify an absolute path
> unambiguously.
>
Not really unambiguously. Consider a function like:
listDirContents("~")
Is "~" a file/dir called "~" in the current working path (which is totally
legal to create) or "/home/<current user>"?
Note that this is how almost all standard libraries behave, except some
that have expansion out of convenience, in higher level languages (not
something like C or Go).
Even Python, which has all shorts of conveniences, doesn't expand tildes:
>>> open("~")
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> IOError: [Errno 2] No such file or directory: '~'
And the equilavent abspath treats the "~" as a "~" file in the local dir
(/Users/username/ was not expanded from ~ -- I just happened to run the
command from there):
>>> import os
> >>> os.path.abspath("~")
> '/Users/username/~'
> >>>
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