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crash —— 自带的计算器和转换器

发布时间 2023-09-23 23:00:04作者: 摩斯电码

crash提供了eval命令，实现了一些很好用的功能，下面学习一下。

格式：
eval [-b][-l] (表达式) | 值

支持的运算符：+ - & | ^ * % / << >>

下面是需要注意的：

  1. 括号并不是必须的，但是如果使用了|、<<或者>>，那么需要使用括号
   crash> eval (1 << 32)
   hexadecimal: 100000000  (4GB)
       decimal: 4294967296
         octal: 40000000000
        binary: 0000000000000000000000000000000100000000000000000000000000000000
  1. 传给eval的值可以是数字（10进制或者16进制），也可以符号，比如如果传入函数名或者全局变量名，返回函数或者全局变量的地址。
crash> eval panic_on_oops
hexadecimal: ffffffff844c3dc4
    decimal: 18446744071634173380  (-2075378236)
      octal: 1777777777760423036704
     binary: 1111111111111111111111111111111110000100010011000011110111000100
crash>
crash> rd panic_on_oops
ffffffff844c3dc4:  0000000000000001                    ........
  1. 如果传给eval的值是16进制，0x并不是必须的，比如有a~f
crash> eval 10
hexadecimal: a
    decimal: 10
      octal: 12
     binary: 0000000000000000000000000000000000000000000000000000000000001010

crash> eval 0x10
hexadecimal: 10
    decimal: 16
      octal: 20
     binary: 0000000000000000000000000000000000000000000000000000000000010000

crash> eval 1a
hexadecimal: 1a
    decimal: 26
      octal: 32
     binary: 0000000000000000000000000000000000000000000000000000000000011010

crash> eval 0x1a
hexadecimal: 1a
    decimal: 26
      octal: 32
     binary: 0000000000000000000000000000000000000000000000000000000000011010
  1. 数字后面可以跟K/k M/m G/g，这里1K表示1024,1M表示10241024，1G表示10241024*1024
crash> eval 1k
hexadecimal: 400  (1KB)
    decimal: 1024
      octal: 2000
     binary: 0000000000000000000000000000000000000000000000000000010000000000

crash> eval 8*2k
hexadecimal: 4000  (16KB)
    decimal: 16384
      octal: 40000
     binary: 0000000000000000000000000000000000000000000000000100000000000000

crash> eval 0x10m
hexadecimal: 1000000  (16MB)
    decimal: 16777216
      octal: 100000000
     binary: 0000000000000000000000000000000000000001000000000000000000000000

crash> eval 1k*1k
hexadecimal: 100000  (1MB)
    decimal: 1048576
      octal: 4000000
     binary: 0000000000000000000000000000000000000000000100000000000000000000

crash> eval 1k*1G
hexadecimal: 10000000000  (1024GB)
    decimal: 1099511627776
      octal: 20000000000000
     binary: 0000000000000000000000010000000000000000000000000000000000000000
  1. 可以在数字前面使用~表示取反
crash> eval ~2
hexadecimal: fffffffffffffffd
    decimal: 18446744073709551613  (-3)
      octal: 1777777777777777777775
     binary: 1111111111111111111111111111111111111111111111111111111111111101

crash> eval ~a
hexadecimal: fffffffffffffff5
    decimal: 18446744073709551605  (-11)
      octal: 1777777777777777777765
     binary: 1111111111111111111111111111111111111111111111111111111111110101
  1. 查看负数的表示
crash> eval -1
hexadecimal: ffffffffffffffff
    decimal: 18446744073709551615  (-1)
      octal: 1777777777777777777777
     binary: 1111111111111111111111111111111111111111111111111111111111111111
crash> eval -a
hexadecimal: fffffffffffffff6
    decimal: 18446744073709551606  (-10)
      octal: 1777777777777777777766
     binary: 1111111111111111111111111111111111111111111111111111111111110110

  1. 如果需要按64位计算，那么可以在数字前面使用-l参数。但是如果本身传入数字就是64位的，那么就不用传-l。如果是在64系统上，都是按64位计算，不需要传-l

  2. 有时我们想知道一个数字的那些位是1，那么需要在数字前面使用-b参数

crash> eval -b 0x5
hexadecimal: 5
    decimal: 5
      octal: 5
     binary: 0000000000000000000000000000000000000000000000000000000000000101
   bits set: 2 0
crash> eval -b 0xa5
hexadecimal: a5
    decimal: 165
      octal: 245
     binary: 0000000000000000000000000000000000000000000000000000000010100101
   bits set: 7 5 2 0

crash> eval -b  -1
hexadecimal: ffffffffffffffff
    decimal: 18446744073709551615  (-1)
      octal: 1777777777777777777777
     binary: 1111111111111111111111111111111111111111111111111111111111111111
   bits set: 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42
             41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20
             19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0