How can I know if I am running in a 64bits or a 32bits linux from within a perl script?

I don’t want to directly access the shell (for example to use uname). I am looking for a fast-forward way to detect the architecture (only if it is 32 or 64 bits), once I know I am on linux.

Answer

There are 3 separate questions you could be asking:

Note for all that there’s not a single magic “64-bit”, there’s lots of different things that could mean.

1. What’s the hardware? — /proc/cpuinfo contains this info in a hard to parse manner. You basically need to have a table of what the different CPUs are. I believe you’ll get numbers bigger than 32 in an “address sizes” if the kernel is 64-bit, though.
2. What’s the OS/kernel? — I believe use POSIX; and inspecting (POSIX::uname())[4] is the canonical answer, but -d /lib64, -d /usr/lib64 being true is also a good indicator.
3. Is this a 64-bit perl? — use Config; and look at $Config{archname}, $Config{myarchname}, $Config{use64bitint}, or some other variable in Config that matches up to what you believe “64 bit” means.