4

I'm writing a program in Java and I need to determine the architecture for which Linux was compiled.

I need something like uname -m, but without running any program, but instead from the /proc pseduo-fs.

What is a reliable source to read from?

Improve this question
5
  • Check the output of cat /proc/version or cat /proc/cpuinfo. Commented Apr 5, 2016 at 18:23
  • 1
    As for /proc/version, you can have a 64-bit cpu with a 32-bit linux installed Commented Apr 5, 2016 at 19:10
  • Why can't you use uname -m? Commented Apr 5, 2016 at 21:13
  • To give you a good answer we really need to know what you want to do with the information... Commented Apr 5, 2016 at 21:15
  • as an intestering tidbit getconf LONG_BIT opens libcxxx.so header to see it it is a 32 or 64 bits binary and returns accordingly 32 or 64 Commented Apr 6, 2016 at 5:25

4 Answers 4

Reset to default
2

As you can have a 32-bit Linux installed in a 64-bit machine, the safer way seems to be verifying CPU capabilities. For Intel and compatible processors:

grep -o -w 'lm' /proc/cpuinfo

http://www.unixtutorial.org/2009/05/how-to-confirm-if-your-cpu-is-32bit-or-64bit/

What you're looking for is the following flag: lm. It stands for X86_FEATURE_LM, the Long Mode (64bit) support. If you can find the "lm" flag among your CPU flags, this means you're looking at a 64bit capable processor.

Improve this answer
1

Everything I'm seeing tells me that the unamebinary simply makes a syscall to uname() to get it's information, so this may be more difficult that you want. If you're willing to implement some JNI, I'd recommend going doing so and issuing the syscall. The closest valuable pseudo file from /proc I can find is /proc/sys/kernel/osrelease, which on my system has contents of 4.2.3-300.fc23.x86_64. This will change with versions, and may change dramatically between flavors of Linux, so it may not be as reliable as you need.

Improve this answer
1
  • on my system cat /proc/sys/kernel/osrelease do not include information about architecture :) it is like this: 4.1.15-gentoo-r1-scantlight3 Commented Apr 5, 2016 at 19:47
0

It looks like there is no file with line with uname -m output, i.e. x86_64 or ppc64le. Arch is not stored in /proc/cpuinfo nor in files in /proc/sys/kernel/.

But maybe slightly better than to parse /proc/cpuinfo (Rui F Ribeiro's xaccepted answer) is to parse /sys/devices/system/cpu/modalias:

$ cat /sys/devices/system/cpu/modalias # x86_64 cpu:type:x86,ven0000fam0006mod005E:feature:,0000,0001,0002,0003... $ cat /sys/devices/system/cpu/modalias # s390x cpu:type:z13:feature:,0000,0001,0002,0003,0004,0005,0006,0007,0008,0009,000A,000B

But then there is a question how to map these.

BTW in kernel it's defined as UTS_MACHINE := $(ARCH) in Makefile and if needed adjusted by archs:

x86{,_64}:

ifeq ($(CONFIG_X86_32),y) ... UTS_MACHINE := i386 ... else ... UTS_MACHINE := x86_64 ...

powerpc: ppc{,64,64le}:

UTS_MACHINE := $(subst $(space),,$(machine-y))

s390x:

UTS_MACHINE := s390x

aarch64:

ifeq ($(CONFIG_CPU_BIG_ENDIAN), y) ... UTS_MACHINE := aarch64_be else ... UTS_MACHINE := aarch64 endif
Improve this answer
-4

Try uname command.

$ man uname

or

$ uname -a

See ya,

Improve this answer
1
  • 5
    The OP specifically asked for something not uname; something reading from the /proc filesystem. Commented Apr 5, 2016 at 18:13

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.