echo $0 will tell you the exact path if it was so executed as a login shell (or otherwise with a full path). If the shell was executed otherwise, then 'which $0' will tell you where it came from, because it must have come from $PATH.
> If the shell was executed otherwise, then 'which $0' will tell you where it came from, because it must have come from $PATH.
Not true: you can be in a shell not in $PATH, and if you executed it from a relative path, which $0 will not find it if you cd to a different location.
