[Linux]man asciiコマンドを利用して、アスキー文字コード表を一瞬で確認する

カテゴリ: Linux

Linuxではmanコマンドを利用することでコマンドのヘルプを見ることができますが、用意されているのはコマンドのヘルプだけではありません。

例えば、下記のようにman asciiコマンドを実行することで、アスキーコード表を素早く確認する事ができます。

man ascii

NAME                                                                                   
       ascii - ASCII character set encoded in octal, decimal, and hexadecimal          

DESCRIPTION                                                                            
       ASCII is the American Standard Code for Information Interchange.  
       It is a 7-bit part of ASCII is known as ISO 646.                                              

       The following table contains the 128 ASCII characters.                          

       C program '\X' escapes are noted.                                               

       Oct   Dec   Hex   Char                        Oct   Dec   Hex   Char            
       ────────────────────────────────────────────────────────────────────────        
       000   0     00    NUL '\0'                    100   64    40    @               
       001   1     01    SOH (start of heading)      101   65    41    A               
       002   2     02    STX (start of text)         102   66    42    B               
       003   3     03    ETX (end of text)           103   67    43    C               
       004   4     04    EOT (end of transmission)   104   68    44    D               
       005   5     05    ENQ (enquiry)               105   69    45    E               
       006   6     06    ACK (acknowledge)           106   70    46    F               
       007   7     07    BEL '\a' (bell)             107   71    47    G               
       010   8     08    BS  '\b' (backspace)        110   72    48    H               
       011   9     09    HT  '\t' (horizontal tab)   111   73    49    I               
       012   10    0A    LF  '\n' (new line)         112   74    4A    J               
       013   11    0B    VT  '\v' (vertical tab)     113   75    4B    K               
       014   12    0C    FF  '\f' (form feed)        114   76    4C    L               
       015   13    0D    CR  '\r' (carriage ret)     115   77    4D    M               
       016   14    0E    SO  (shift out)             116   78    4E    N               
       017   15    0F    SI  (shift in)              117   79    4F    O               
       020   16    10    DLE (data link escape)      120   80    50    P               
       021   17    11    DC1 (device control 1)      121   81    51    Q               
       022   18    12    DC2 (device control 2)      122   82    52    R               
       023   19    13    DC3 (device control 3)      123   83    53    S               
       024   20    14    DC4 (device control 4)      124   84    54    T               
       025   21    15    NAK (negative ack.)         125   85    55    U               
       026   22    16    SYN (synchronous idle)      126   86    56    V               
       027   23    17    ETB (end of trans. blk)     127   87    57    W               
       030   24    18    CAN (cancel)                130   88    58    X               
       031   25    19    EM  (end of medium)         131   89    59    Y               
       032   26    1A    SUB (substitute)            132   90    5A    Z               
       033   27    1B    ESC (escape)                133   91    5B    [               
       034   28    1C    FS  (file separator)        134   92    5C    \  '\\'         
       035   29    1D    GS  (group separator)       135   93    5D    ]               
       036   30    1E    RS  (record separator)      136   94    5E    ^               
       037   31    1F    US  (unit separator)        137   95    5F    _               
       040   32    20    SPACE                       140   96    60    `               
       041   33    21    !                           141   97    61    a               
       042   34    22    "                           142   98    62    b               
       043   35    23    #                           143   99    63    c               
       044   36    24    $                           144   100   64    d               
       045   37    25    %                           145   101   65    e               
       046   38    26    &                           146   102   66    f               
       047   39    27    ´                           147   103   67    g               
       050   40    28    (                           150   104   68    h               
       051   41    29    )                           151   105   69    i               
       052   42    2A    *                           152   106   6A    j               
       053   43    2B    +                           153   107   6B    k               
       054   44    2C    ,                           154   108   6C    l               
       055   45    2D    -                           155   109   6D    m               
       056   46    2E    .                           156   110   6E    n               
       057   47    2F    /                           157   111   6F    o               

       060   48    30    0                           160   112   70    p               
       061   49    31    1                           161   113   71    q               
       062   50    32    2                           162   114   72    r               
       063   51    33    3                           163   115   73    s               
       064   52    34    4                           164   116   74    t
       065   53    35    5                           165   117   75    u
       066   54    36    6                           166   118   76    v
       067   55    37    7                           167   119   77    w
       070   56    38    8                           170   120   78    x
       071   57    39    9                           171   121   79    y
       072   58    3A    :                           172   122   7A    z
       073   59    3B    ;                           173   123   7B    {
       074   60    3C    <                           174   124   7C    |
       075   61    3D    =                           175   125   7D    }
       076   62    3E    >                           176   126   7E    ~
       077   63    3F    ?                           177   127   7F    DEL

   Tables
       For convenience, let us give more compact tables in hex and decimal.

          2 3 4 5 6 7       30 40 50 60 70 80 90 100 110 120
        -------------      ---------------------------------
       0:   0 @ P ` p     0:    (  2  <  F  P  Z  d   n   x
       1: ! 1 A Q a q     1:    )  3  =  G  Q  [  e   o   y
       2: " 2 B R b r     2:    *  4  >  H  R  \  f   p   z
       3: # 3 C S c s     3: !  +  5  ?  I  S  ]  g   q   {
       4: $ 4 D T d t     4: "  ,  6  @  J  T  ^  h   r   |
       5: % 5 E U e u     5: #  -  7  A  K  U  _  i   s   }
       6: & 6 F V f v     6: $  .  8  B  L  V  `  j   t   ~
       7: ´ 7 G W g w     7: %  /  9  C  M  W  a  k   u  DEL
       8: ( 8 H X h x     8: &  0  :  D  N  X  b  l   v
       9: ) 9 I Y i y     9: ´  1  ;  E  O  Y  c  m   w
       A: * : J Z j z
       B: + ; K [ k {
       C: , < L \ l |
       D: - = M ] m }
       E: . > N ^ n ~
       F: / ? O _ o DEL
...

ほかにも、man unitsコマンドでは、kiro, mega, nanoなどコンピュータよく使われる単位の接尾語一覧を確認することもできます。

UNITS(7)                                                                                             Linux Programmer's Manual                                                                                             UNITS(7)

NAME
       units, kilo, kibi, mega, mebi, giga, gibi - decimal and binary prefixes

DESCRIPTION
   Decimal prefixes
       The SI system of units uses prefixes that indicate powers of ten.  A kilometer is 1000 meter, and a megawatt is 1000000 watt.  Below the standard prefixes.

              Prefix   Name    Value
              y        yocto   10^-24 = 0.000000000000000000000001
              z        zepto   10^-21 = 0.000000000000000000001
              a        atto    10^-18 = 0.000000000000000001
              f        femto   10^-15 = 0.000000000000001
              p        pico    10^-12 = 0.000000000001
              n        nano    10^-9  = 0.000000001
              µ        micro   10^-6  = 0.000001
              m        milli   10^-3  = 0.001
              c        centi   10^-2  = 0.01
              d        deci    10^-1  = 0.1
              da       deka    10^ 1  = 10
              h        hecto   10^ 2  = 100
              k        kilo    10^ 3  = 1000
              M        mega    10^ 6  = 1000000
              G        giga    10^ 9  = 1000000000
              T        tera    10^12  = 1000000000000
              P        peta    10^15  = 1000000000000000
              E        exa     10^18  = 1000000000000000000
              Z        zetta   10^21  = 1000000000000000000000
              Y        yotta   10^24  = 1000000000000000000000000

       The symbol for micro is the Greek letter mu, often written u in an ASCII context where this Greek letter is not available.  See also

              ⟨http://physics.nist.gov/cuu/Units/prefixes.html⟩

   Binary prefixes
       The  binary prefixes resemble the decimal ones, but have an additional 'i' (and "Ki" starts with a capital 'K').  The names are formed by taking the first syllable of the names of the decimal prefix with roughly the same
       size, followed by "bi" for "binary".

              Prefix   Name   Value
              Ki       kibi   2^10 = 1024
              Mi       mebi   2^20 = 1048576
              Gi       gibi   2^30 = 1073741824
              Ti       tebi   2^40 = 1099511627776
              Pi       pebi   2^50 = 1125899906842624
              Ei       exbi   2^60 = 1152921504606846976

       See also

       ⟨http://physics.nist.gov/cuu/Units/binary.html⟩

   Discussion
       Before these binary prefixes were introduced, it was fairly common to use k=1000 and K=1024, just like b=bit, B=byte.  Unfortunately, the M is capital already, and cannot be capitalized to indicate binary-ness.

       At first that didn't matter too much, since memory modules and disks came in sizes that were powers of two, so everyone knew that in such contexts "kilobyte" and "megabyte" meant 1024  and  1048576  bytes,  respectively.
       What  originally  was  a sloppy use of the prefixes "kilo" and "mega" started to become regarded as the "real true meaning" when computers were involved.  But then disk technology changed, and disk sizes became arbitrary
       numbers.  After a period of uncertainty all disk manufacturers settled on the standard, namely k=1000, M=1000k, G=1000M.

       The situation was messy: in the 14k4 modems, k=1000; in the 1.44MB diskettes, M=1024000; etc.  In 1998 the IEC approved the standard that defines the binary prefixes given above, enabling people to be precise  and  unam‐
       biguous.

       Thus, today, MB = 1000000B and MiB = 1048576B.

       In the free software world programs are slowly being changed to conform.  When the Linux kernel boots and says

              hda: 120064896 sectors (61473 MB) w/2048KiB Cache

       the MB are megabytes and the KiB are kibibytes.
...
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