Re (chip): Two-arg open() considered dangerous

[chip]

I agree that three-arg open is a bit new to depend on, but sysopen may not be inconvenient. Specifically, it's guaranteed{1} that O_RDONLY, O_WRONLY, and O_RDWR have the values zero, one, and two, respectively. So sysopen FOO, $file, 0 should work everywhere in the known universe.

{1} This is OK to count on because the C function open() originates with Unix, and for backwards compatibility with ancient UNIX code, the second parameter of open() must accept zero/one/two.

    -- Chip Salzenberg, Free-Floating Agent of Chaos

[tilly]

It is not guaranteed. From 'perldoc -f sysopen' on 5.005_03 I get:

=item sysopen FILEHANDLE,FILENAME,MODE

=item sysopen FILEHANDLE,FILENAME,MODE,PERMS

[ snip ]

The possible values and flag bits of the MODE parameter are
system-dependent; they are available via the standard module C<Fcntl>.
For historical reasons, some values work on almost every system
supported by perl: zero means read-only, one means write-only, and two
means read/write.  We know that these values do I<not> work under
OS/390 & VM/ESA Unix and on the Macintosh; you probably don't want to
use them in new code.

So those values probably work. But not always.

[chip]

Damn. I had no idea that there were systems that broken that could still run a modern Perl.

    -- Chip Salzenberg, Free-Floating Agent of Chaos

[ichimunki]

Either way, it's more readable with the explicit constant names exported by Fcntl, which is good for all those coders coming to your code from a two-arg open() mentality/background.