[t43562]

arg0 also contains the path from where the invoker invoked the binary so for me this enables all sorts of binaries that work out where their dependencies are relative to their original binary. That's extremely convenient because you can combine it with $PWD to find out the absolute path to the binary.

One can then guess what the PYTHONPATH and LD_LIBRARY_PATH should be most of the time and save someone from having to set them.

Obviously this is of most use when you're running something you've installed into /opt (e.g. /opt/myprog/bin, /opt/myprog/lib etc) or are running it from the source tree.

[account42]

> arg0 also contains the path from where the invoker invoked the binary

Not in general it doesn't. Convention for shells is to pass the string the user used to invoke the program which may be an absolute path, a relative path or just a filename resolved against $PATH.

> this enables all sorts of binaries that work out where their dependencies are relative to their original binary

You should use the OS-specific functions to retrieve the current executable path for that - GetModuleFileName(NULL, ...) on Windows and readlink("/proc/self/exe", ...) on Linux. For script look into your interpreter documentation - e.g. Bash has ${BASH_SOURCE[0]}. Unfortunately POSIX shell scripts are SOL and have to rely on $0 plus some $PATH searching.