可以直接查看/proc/cpuinfo文件，其中有关于CPU的详细信息，包括型号、CACHE、频率等等，但是没有地方明确的写明是32位还是64位的，不过在FLAG那一行有很多的标志信息，如果其中有LM标志，说明这个是64位的CPU，如果没有，则说明是32位的。

FLAG的详细的解释是定义在cpufeature.h头文件中的，里面关于LM的解释是Long Mode (x86-64)，这个文件在64位系统上位于/usr/include/asm-x86_64目录下，在32位系统中位于/usr/include/asm目录下，下面列一个64位的cpufeature的头文件做个记录吧

#define X86_FEATURE_FPU (0*32+ 0) /* Onboard FPU */
#define X86_FEATURE_VME (0*32+ 1) /* Virtual Mode Extensions */
#define X86_FEATURE_DE (0*32+ 2) /* Debugging Extensions */
#define X86_FEATURE_PSE (0*32+ 3) /* Page Size Extensions */
#define X86_FEATURE_TSC (0*32+ 4) /* Time Stamp Counter */
#define X86_FEATURE_MSR (0*32+ 5) /* Model-Specific Registers, RDMSR, WRMSR */
#define X86_FEATURE_PAE (0*32+ 6) /* Physical Address Extensions */
#define X86_FEATURE_MCE (0*32+ 7) /* Machine Check Architecture */
#define X86_FEATURE_CX8 (0*32+ 8) /* CMPXCHG8 instruction */
#define X86_FEATURE_APIC (0*32+ 9) /* Onboard APIC */
#define X86_FEATURE_SEP (0*32+11) /* SYSENTER/SYSEXIT */
#define X86_FEATURE_MTRR (0*32+12) /* Memory Type Range Registers */
#define X86_FEATURE_PGE (0*32+13) /* Page Global Enable */
#define X86_FEATURE_MCA (0*32+14) /* Machine Check Architecture */
#define X86_FEATURE_CMOV (0*32+15) /* CMOV instruction (FCMOVCC and FCOMI too if FPU present) */
#define X86_FEATURE_PAT (0*32+16) /* Page Attribute Table */
#define X86_FEATURE_PSE36 (0*32+17) /* 36-bit PSEs */
#define X86_FEATURE_PN (0*32+18) /* Processor serial number */
#define X86_FEATURE_CLFLSH (0*32+19) /* Supports the CLFLUSH instruction */
#define X86_FEATURE_DTES (0*32+21) /* Debug Trace Store */
#define X86_FEATURE_ACPI (0*32+22) /* ACPI via MSR */
#define X86_FEATURE_MMX (0*32+23) /* Multimedia Extensions */
#define X86_FEATURE_FXSR (0*32+24) /* FXSAVE and FXRSTOR instructions (fast save and restore */
/* of FPU context), and CR4.OSFXSR available */
#define X86_FEATURE_XMM (0*32+25) /* Streaming SIMD Extensions */
#define X86_FEATURE_XMM2 (0*32+26) /* Streaming SIMD Extensions-2 */
#define X86_FEATURE_SELFSNOOP (0*32+27) /* CPU self snoop */
#define X86_FEATURE_ACC (0*32+29) /* Automatic clock control */
#define X86_FEATURE_IA64 (0*32+30) /* IA-64 processor */

/* AMD-defined CPU features, CPUID level 0x80000001, word 1 */
/* Don't duplicate feature flags which are redundant with Intel! */
#define X86_FEATURE_SYSCALL (1*32+11) /* SYSCALL/SYSRET */
#define X86_FEATURE_MMXEXT (1*32+22) /* AMD MMX extensions */
#define X86_FEATURE_LM (1*32+29) /* Long Mode (x86-64) */
#define X86_FEATURE_3DNOWEXT (1*32+30) /* AMD 3DNow! extensions */
#define X86_FEATURE_3DNOW (1*32+31) /* 3DNow! */

/* Transmeta-defined CPU features, CPUID level 0x80860001, word 2 */
#define X86_FEATURE_RECOVERY (2*32+ 0) /* CPU in recovery mode */
#define X86_FEATURE_LONGRUN (2*32+ 1) /* Longrun power control */
#define X86_FEATURE_LRTI (2*32+ 3) /* LongRun table interface */

/* Other features, Linux-defined mapping, word 3 */
/* This range is used for feature bits which conflict or are synthesized */
#define X86_FEATURE_CXMMX (3*32+ 0) /* Cyrix MMX extensions */
#define X86_FEATURE_K6_MTRR (3*32+ 1) /* AMD K6 nonstandard MTRRs */
#define X86_FEATURE_CYRIX_ARR (3*32+ 2) /* Cyrix ARRs (= MTRRs) */
#define X86_FEATURE_CENTAUR_MCR (3*32+ 3) /* Centaur MCRs (= MTRRs) */