On Apr 12, 2007, at 4:50 AM, Pietro Abate wrote:

> why the Unix.getlogin function returns "no such file or directory"
> if the unix getlogin() function returns null (see getlogin.c) ?
>
> ex:
> -----------
> let main () =
>   try
>       print_string (Unix.getlogin())
>   with Unix.Unix_error(e,_,_) ->
>       failwith (Unix.error_message e)
> ;;
>
> main ()
> ---------
>
> echo "a" | ./a.out
> Fatal error: exception Failure(No such file or directory")
>
> How can I use getlogin if I want to pass something on the standard  
> input
> to my program ?
>
> The same example works with MacOsX. Why this difference ?

It looks like OCaml simply calls the operating system's  
implementation of getlogin().  I ran into a similar issue with Python  
code a while back, so that's where my experience with this comes from.

The problem is that it seems not all Unix-like operating systems  
implement getlogin() in exactly the same way.  For example, getlogin 
() under Linux dies with the "No such file or directory" error when  
standard-in is not a terminal.  getlogin() under Mac OS X doesn't  
seem to care what standard-in is.  The man pages for getlogin might  
say something about this, as well.

My solution was to use getpwuid(getuid()) instead of getlogin().

Cheers,
Brian