failed to detect scriptname on read only file system

[contrun]

The function os.scriptname uses rename to detect if a file exists. Rename will always fail on my nixos machine as the executable lies in a read only file system. Here is the log after adding print(name, ok, err, code) to the function os.path.exists. Actually file /nix/store/99p0nyqgayic2ipqx2x4lr4njl8f5nrz-python3-3.6.8/bin/realpath do exist.

 lua ~/.z.lua/z.lua --init zsh                                                                                              ~
/nix/store/99p0nyqgayic2ipqx2x4lr4njl8f5nrz-python3-3.6.8/bin/realpath  nil     Read-only file system   30
/home/e/bin/realpath    nil     No such file or directory       2
/run/wrappers/bin/realpath      nil     No such file or directory       2
/home/e/.bin/realpath   nil     No such file or directory       2
/home/e/.bin/realpath   nil     No such file or directory       2
/home/e/.local/bin/realpath     nil     No such file or directory       2
/home/e/.cabal/bin/realpath     nil     No such file or directory       2
/home/e/.cargo/bin/realpath     nil     No such file or directory       2
/home/e/Local/go/bin/realpath   nil     No such file or directory       2
/home/e/.node/node_modules/.bin/realpath        nil     No such file or directory       2
/usr/local/bin/realpath nil     No such file or directory       2
/usr/bin/realpath       nil     No such file or directory       2
/bin/realpath   nil     No such file or directory       2
/home/e/.nix-profile/bin/realpath       nil     Read-only file system   30
/nix/var/nix/profiles/default/bin/realpath      nil     No such file or directory       2
/run/current-system/sw/bin/realpath     nil     Read-only file system   30
/etc/profiles/per-user/e/bin/realpath   nil     No such file or directory       2
/nix/store/99p0nyqgayic2ipqx2x4lr4njl8f5nrz-python3-3.6.8/bin/perl      nil     Read-only file system   30
/home/e/bin/perl        nil     No such file or directory       2
/run/wrappers/bin/perl  nil     No such file or directory       2
/home/e/.bin/perl       nil     No such file or directory       2
/home/e/.bin/perl       nil     No such file or directory       2
/home/e/.local/bin/perl nil     No such file or directory       2
/home/e/.cabal/bin/perl nil     No such file or directory       2
/home/e/.cargo/bin/perl nil     No such file or directory       2
/home/e/Local/go/bin/perl       nil     No such file or directory       2
/home/e/.node/node_modules/.bin/perl    nil     No such file or directory       2
/usr/local/bin/perl     nil     No such file or directory       2
/usr/bin/perl   nil     No such file or directory       2
/bin/perl       nil     No such file or directory       2
/home/e/.nix-profile/bin/perl   nil     Read-only file system   30
/nix/var/nix/profiles/default/bin/perl  nil     No such file or directory       2
/run/current-system/sw/bin/perl nil     Read-only file system   30
/etc/profiles/per-user/e/bin/perl       nil     No such file or directory       2
/nix/store/99p0nyqgayic2ipqx2x4lr4njl8f5nrz-python3-3.6.8/bin/python    nil     Read-only file system   30
/home/e/bin/python      nil     No such file or directory       2
/run/wrappers/bin/python        nil     No such file or directory       2
/home/e/.bin/python     nil     No such file or directory       2
/home/e/.bin/python     nil     No such file or directory       2
/home/e/.local/bin/python       nil     No such file or directory       2
/home/e/.cabal/bin/python       nil     No such file or directory       2
/home/e/.cargo/bin/python       nil     No such file or directory       2
/home/e/Local/go/bin/python     nil     No such file or directory       2
/home/e/.node/node_modules/.bin/python  nil     No such file or directory       2
/usr/local/bin/python   nil     No such file or directory       2
/usr/bin/python nil     No such file or directory       2
/bin/python     nil     No such file or directory       2
/home/e/.nix-profile/bin/python nil     Read-only file system   30
/nix/var/nix/profiles/default/bin/python        nil     No such file or directory       2
/run/current-system/sw/bin/python       nil     Read-only file system   30
/etc/profiles/per-user/e/bin/python     nil     No such file or directory       2
/nix/store/99p0nyqgayic2ipqx2x4lr4njl8f5nrz-python3-3.6.8/bin/python2   nil     Read-only file system   30
/home/e/bin/python2     nil     No such file or directory       2
/run/wrappers/bin/python2       nil     No such file or directory       2
/home/e/.bin/python2    nil     No such file or directory       2
/home/e/.bin/python2    nil     No such file or directory       2
/home/e/.local/bin/python2      nil     No such file or directory       2
/home/e/.cabal/bin/python2      nil     No such file or directory       2
/home/e/.cargo/bin/python2      nil     No such file or directory       2
/home/e/Local/go/bin/python2    nil     No such file or directory       2
/home/e/.node/node_modules/.bin/python2 nil     No such file or directory       2
/usr/local/bin/python2  nil     No such file or directory       2
/usr/bin/python2        nil     No such file or directory       2
/bin/python2    nil     No such file or directory       2
/home/e/.nix-profile/bin/python2        nil     Read-only file system   30
/nix/var/nix/profiles/default/bin/python2       nil     No such file or directory       2
/run/current-system/sw/bin/python2      nil     Read-only file system   30
/etc/profiles/per-user/e/bin/python2    nil     No such file or directory       2
/nix/store/99p0nyqgayic2ipqx2x4lr4njl8f5nrz-python3-3.6.8/bin/python3   nil     Read-only file system   30
/home/e/bin/python3     nil     No such file or directory       2
/run/wrappers/bin/python3       nil     No such file or directory       2
/home/e/.bin/python3    nil     No such file or directory       2
/home/e/.bin/python3    nil     No such file or directory       2
/home/e/.local/bin/python3      nil     No such file or directory       2
/home/e/.cabal/bin/python3      nil     No such file or directory       2
/home/e/.cargo/bin/python3      nil     No such file or directory       2
/home/e/Local/go/bin/python3    nil     No such file or directory       2
/home/e/.node/node_modules/.bin/python3 nil     No such file or directory       2
/usr/local/bin/python3  nil     No such file or directory       2
/usr/bin/python3        nil     No such file or directory       2
/bin/python3    nil     No such file or directory       2
/home/e/.nix-profile/bin/python3        nil     Read-only file system   30
/nix/var/nix/profiles/default/bin/python3       nil     No such file or directory       2
/run/current-system/sw/bin/python3      nil     Read-only file system   30
/etc/profiles/per-user/e/bin/python3    nil     No such file or directory       2
lua: /home/e/.z.lua/z.lua:1415: attempt to concatenate a nil value
stack traceback:
        /home/e/.z.lua/z.lua:1415: in function 'z_shell_init'
        /home/e/.z.lua/z.lua:1150: in function 'main'
        /home/e/.z.lua/z.lua:1696: in main chunk
        [C]: in ?

[skywind3000]

It's strange, os.path.exists works on my linux, it can return true for /usr/bin (current user doesn't have write permission on it).

So, I cannot reproduce your problem on my linux or freebsd servers.

Do you have any idea how to detect file existence on nixos ??

[contrun]

I tried the method to check if a file exists provided on stackoverflow. This works on my nixos machine. Still, it may not work for files which the user has no read permission to the file and it is a read only file system.