Michael Norrish wrote:
Incidentally, on the machine where Posix.Process.exec("/bin/ls", [])
seg. faults, Unix.execute("/bin/ls", []) works correctly. The Basis
library documentation I have for the Unix structure doesn't discuss how
the argv component should be setup, but attempting
Unix.execute("/bin/ls", ["ls"])
prompts a message from ls saying that there is no file called ls.
This doesn't seem consistent.
Curiously, on the Macbook where Posix.Process.exec gives ENOTSUP,
Unix.execute does work.
It turns out that on Mac OS X execv returns ENOTSUP if the process is
multi-threaded. You need to use Posix.Process.fork first to start a new
process:
case Posix.Process.fork() of
SOME _ => OS.Process.exit OS.Process.success
| NONE => Posix.Process.exec("/bin/ls", ["ls"]);
This isn't documented in Apple's man page for execv and I found the
explanation at
http://factor-language.blogspot.com/2007/07/execve-returning-enotsup-on-mac-os-x.html
Unix.execute is implemented in terms of fork and exec and the exec is
called in the child process, roughly the code above.
The arguments for Posix.Process.exec and Unix.execute are different.
The basis library book (Ganser and Reppy 2004) says for Unix.execute
"execute(cmd, args) asks the operating system to execute the program
named by the string cmd with the argument list args." For
Posix.Process.exec it says "The args argument is a list of string
arguments to be passed to the new program. By convention, the first
item in args is some form of the filename of the new program, usually
the last arc in the path or filename." Like any informal specification
this is subject to interpretation but I think the current behaviour
conforms to this definition.
David
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