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coreutils: shuf invocation

 
 7.2 ‘shuf’: Shuffling text
 ==========================
 
 ‘shuf’ shuffles its input by outputting a random permutation of its
 input lines.  Each output permutation is equally likely.  Synopses:
 
      shuf [OPTION]... [FILE]
      shuf -e [OPTION]... [ARG]...
      shuf -i LO-HI [OPTION]...
 
    ‘shuf’ has three modes of operation that affect where it obtains its
 input lines.  By default, it reads lines from standard input.  The
 following options change the operation mode:
 
 ‘-e’
 ‘--echo’
      Treat each command-line operand as an input line.
 
 ‘-i LO-HI’
 ‘--input-range=LO-HI’
      Act as if input came from a file containing the range of unsigned
      decimal integers LO...HI, one per line.
 
    ‘shuf’’s other options can affect its behavior in all operation
 modes:
 
 ‘-n COUNT’
 ‘--head-count=COUNT’
      Output at most COUNT lines.  By default, all input lines are
      output.
 
 ‘-o OUTPUT-FILE’
 ‘--output=OUTPUT-FILE’
      Write output to OUTPUT-FILE instead of standard output.  ‘shuf’
      reads all input before opening OUTPUT-FILE, so you can safely
      shuffle a file in place by using commands like ‘shuf -o F <F’ and
      ‘cat F | shuf -o F’.
 
 ‘--random-source=FILE’
      Use FILE as a source of random data used to determine which
      permutation to generate.  Random sources.
 
 ‘-r’
 ‘--repeat’
      Repeat output values, that is, select with replacement.  With this
      option the output is not a permutation of the input; instead, each
      output line is randomly chosen from all the inputs.  This option is
      typically combined with ‘--head-count’; if ‘--head-count’ is not
      given, ‘shuf’ repeats indefinitely.
 
 ‘-z’
 ‘--zero-terminated’
      Delimit items with a zero byte rather than a newline (ASCII LF).
      I.e., treat input as items separated by ASCII NUL and terminate
      output items with ASCII NUL. This option can be useful in
      conjunction with ‘perl -0’ or ‘find -print0’ and ‘xargs -0’ which
      do the same in order to reliably handle arbitrary file names (even
      those containing blanks or other special characters).
 
    For example:
 
      shuf <<EOF
      A man,
      a plan,
      a canal:
      Panama!
      EOF
 
 might produce the output
 
      Panama!
      A man,
      a canal:
      a plan,
 
 Similarly, the command:
 
      shuf -e clubs hearts diamonds spades
 
 might output:
 
      clubs
      diamonds
      spades
      hearts
 
 and the command ‘shuf -i 1-4’ might output:
 
      4
      2
      1
      3
 
 The above examples all have four input lines, so ‘shuf’ might produce
 any of the twenty-four possible permutations of the input.  In general,
 if there are N input lines, there are N!  (i.e., N factorial, or N * (N
 - 1) * ... * 1) possible output permutations.
 
 To output 50 random numbers each in the range 0 through 9, use:
 
      shuf -r -n 50 -i 0-9
 
 To simulate 100 coin flips, use:
 
      shuf -r -n 100 -e Head Tail
 
    An exit status of zero indicates success, and a nonzero value
 indicates failure.
 

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