[pdp7-unix] pdp7-unix Digest, Vol 5, Issue 17

Angelo Papenhoff aap at papnet.eu
Wed Oct 23 06:53:42 AEST 2019


On 22/10/19, Will Senn via pdp7-unix wrote:
> Having a hard time wrapping my head around the ln system cat cat command 
> though! I've read The Evolution of the Unix Time-sharing System a couple 
> of times and still don't understand why this makes sense:
> 
> ln dd ken ken ln ken x x rm ken

in pdp-7 unix everything is relative to the current directory.
commands/system calls take a single file (in the current directory),
some a directory + file combination.
old `ln foo bar quux` has the meaning of modern `ln foo/bar quux`.
Since od takes single files (not a path) as arguments, they have to
be in the current directory.

As for executing commands. The shell will execute a command if it is
either in the current or the system directory. In the latter case it
will be linked first. But this means you can only execute system
commands if you're in a directory you have write permission to.
Yes, it's weird, hence by question on TUHS (to which there is still no
answer).

aap


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