Check if running kernel is 32 bits or 64 bits

test64bits.sh

#!/bin/sh


# Return codes:
# 10 => The kernel is unknow
# 32 => The kernel is 32-bits
# 64 => The kernel is 64-bits
_testkernelbits() {

# Test method 1. Check the lenght of the kernel addresses
if [ -r "/proc/kallsyms" ]; then
	addrlen=$(head -1 /proc/kallsyms|awk '{print $1}'|wc -c)
	if [ ${addrlen} = 17 ]; then 
		return 64
	elif [ ${addrlen} = 9 ]; then
		return 32
	fi
fi

# Test method 2. Check if the kernel knows about CONFIG_64BIT
CURDIR=$(pwd)
TESTDIR=$(mktemp -d)
cd "${TESTDIR}"
cat << EOF > Makefile
ifeq (\$(TEST), 64)
	obj-m := test64bits.o
else
	obj-m := testgeneric.o
endif

PWD   := \$(shell pwd)
KVER  ?= \$(shell uname -r)
KDIR  := /lib/modules/\$(KVER)/build

default:
	make -C \$(KDIR) M=\$(PWD) modules

clean:
	rm -f .*.cmd *.o *.ko *.mod.c modules.order Module.symvers
	rm -fr .tmp_versions
EOF
cat << EOF > testgeneric.c
#include <linux/kobject.h>
int main (void) {
	return 0;
}
EOF
cat << EOF > test64bits.c
#include <linux/kobject.h>
int main (void) {
	int val __attribute__ ((unused));
	val = CONFIG_64BIT;
	return 0;
}
EOF
# Test that module compilation works.
if make > /dev/null 2>&1; then
	make clean > /dev/null 2>&1
	# Test that the kernel is 64 bits.
	if make TEST=64 > /dev/null 2>&1; then
		RETCODE=64
	else
		RETCODE=32
	fi
fi
# Clean
make clean > /dev/null 2>&1
cd "${CURDIR}"
rm -f "${TESTDIR}/Makefile"
rm -f "${TESTDIR}/testgeneric.c"
rm -f "${TESTDIR}/test64bits.c"
rmdir "${TESTDIR}"
if [ -n ${RETCODE} ]; then
	return ${RETCODE}
fi

# Test method 3. Check if the config has CONFIG_64BIT defined.
KCONFIG="/boot/config-$(uname -r)"

if [ -r "$KCONFIG" ]; then
	if grep -q 'CONFIG_64BIT=y' "$KCONFIG"; then
		return 64
	else
		return 32
	fi
fi

# If we reach here we really don't have a clue about this kernel.
return 10

}

_testkernelbits; kernelbits=$?

echo "${kernelbits}"