97

under an intel I know I can look at the outcome of uname -m to know if my OS is 32 or 64 bit, but under ARM this gives:

armv7l

I deduced from

file /usr/bin/ls

that I'm on a 32-bit OS, but how can I know this in an easier way?

9
  • 5
    arm 7 is 32 bit. ARMv8-A architecture, announced in October 2011,[6] adds support for a 64-bit address space and 64-bit arithmetic. — wikipedia Jun 10 '14 at 12:37
  • @richard I was guessing so, but then what is the name of the 64-bit variant?
    – Chris Maes
    Jun 10 '14 at 12:39
  • 1
    I don't have access to an ARM machine but what is the output of uname -a and gcc -v? Those might be helpful.
    – terdon
    Jun 10 '14 at 12:44
  • Announced October 2011, ARMv8-A (often called ARMv8 although not all variants are 64-bit such as ARMv8-R) represents a fundamental change to the ARM architecture. It adds a 64-bit architecture, named "AArch64", and a new "A64" instruction set. AArch64 provides user-space compatibility with ARMv7-A ISA, the 32-bit architecture, therein referred to as "AArch32" and the old 32-bit instruction set, now named "A32" ARM announced their Cortex-A53 and Cortex-A57 cores on 30 October 2012.en.wikipedia.org/wiki/ARM_architecture#64.2F32-bit_architecture Jun 10 '14 at 12:48
  • 1
    Arm was the last of the 32bit cpu to go 64bit (excluding those that died). Most went 64bit and then died, because of poor marketing — assuming that being better is enough. The Intel x86 was the second to last, though it was AMD that added 64 bit. Jun 10 '14 at 12:52
111

There are several gradations, since you can run a 32-bit or mixed operating system on a 64-bit-capable CPU. See 64-bit kernel, but all 32-bit ELF executable running processes, how is this? for a detailed discussion (written for x86, but most of it applies to arm as well).

You can find the processor model in /proc/cpuinfo. For example:

$ cat /proc/cpuinfo
Processor       : ARMv7 Processor rev 10 (v7l)

ARMv7 (and below) is 32-bit. ARMv8 introduces the 64-bit instruction set.

If you want to see whether your system supports 64-bit binaries, check the kernel architecture:

$ uname -m
armv7l

On a 64-bit processor, you'd see a string starting with armv8 (or above) if the uname process itself is a 32-bit process, or aarch64 if it's a 64-bit process. (See also https://stackoverflow.com/questions/45125516/possible-values-for-uname-m)

6
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    I don't contest your answer, but unfortunately android IS A LINUX, so, there suppose to be some command, SOMEWHERE that show it locally and not to read a documentation on some page Feb 6 '15 at 9:04
  • 3
    @THESorcerer Android uses a Linux kernel but it is not a Linux system. It does not have Linux user land tools (only a very small subset). On Android, I think 64-bit support is consistent in the base OS, so cat /proc/$$/maps will let you know whether the system is 64-bit or 32-bit from an adb command line. Feb 6 '15 at 9:11
  • 5
    I believe Raspberry Pi 3, which is ARMv8 (CRC, no optional Crypto) will report armv7l even though its ARMv8. So I'm pretty sure the wrong CPU will be reported.
    – user56041
    Jul 25 '17 at 2:02
  • 3
    @jww If it reports armv7l, it means you're running a 32-bit kernel. You can run a 32-bit kernel on a 64-bit CPU. If you want information about the CPU, read /proc/cpuinfo. Jul 25 '17 at 4:53
  • uname -m just returns "aarch64". /proc/cpuinfo doesn't always contain a name for a processor either.
    – Halsafar
    Sep 4 '19 at 16:52
29

As richard points out, armv7 variants are all 32-bit, so there is no redundant label armv7-32, etc.

On a linux system, you can easily, although not truly definitively, check by examining a common executable:

> which bash
/bin/bash
> file /bin/bash
/bin/bash: ELF 32-bit LSB executable, ARM, version 1 (SYSV) ...

I say "not definitively" because it is possible to run 32-bit executables on a 64-bit system.

There does not appear to be anything foolproof in /proc or /sys; the output from /proc/cpuinfo may provide some significant clues. If for some reason you need an automated check, creating a table mapped to the "model name" field seems like one potentially sound method (other fields, including "model", "cpu family", etc. look optional -- they don't appear at all for me on a Broadcom 2708 ARMv6 processor).

2
  • So armv7l is 32 bit right?
    – bakalolo
    Jun 22 '17 at 21:36
  • 2
    @bakalolo Read the question and the accepted answer slowly ;)
    – goldilocks
    Jun 23 '17 at 10:44
14

Install the 'lshw' package.

# lshw
...
    description: Computer
    product: Raspberry Pi 3 Model B Rev 1.2
    width: 32 bits
...
11

Seems like most ways to see bit count is to somehow know that arm7=32 bit and while that may be true but what about

pi@rpi9:~ $ getconf LONG_BIT
32

And if you want to look for the cpu model I normally use arch

root@rpi4:~# tr '\0' '\n' </proc/device-tree/model;arch
Raspberry Pi Model B Rev 2
armv6l

pi@rpi9:~ $ tr '\0' '\n' </proc/device-tree/model;arch
Raspberry Pi 3 Model B Rev 1.2
armv7l
2
  • 1
    getconf LONG_BIT is very straightforward Oct 25 '19 at 7:14
  • This should be the selected answer; getconf is a POSIX command and it works on Linux, macOS and BSD.
    – legends2k
    Oct 12 at 4:54
1

Try the following.

// -*- compile-command: "gcc -Wall -o sizeof sizeof.c && ./sizeof" -*-

#include <stdio.h>
#include <limits.h>

#define size(t) { t x; printf("%s:\t%3lu bit\n", #t, CHAR_BIT * sizeof x); }

int main (int argc, char *argv[])
{
  size(char);
  size(short);
  size(int);
  size(long);
  size(void*);
  return 0;
}

The address size is void*.

4
-5

Nope it's a 64-bit computer. It's an Allwinner H8, witch is a double ARM-7. 8 cores, 64 bits, powervr, sgx 544, at double speed (700mhz).

So no, it's capable of being 64 bit. Just the OS might be 32.

2
  • where did you find that the OP's using Allwinner H8? The architecture is armv7l which is clearly not a 64-bit one
    – phuclv
    May 3 '17 at 2:00
  • It's better to demonstrate a way to find the desired information from within the system instead of using third-party information from external sources. This is better suited to be a comment than an answer (hence all the down-votes).
    – Synetech
    Sep 20 '19 at 3:13

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