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File: coreutils.info,  Node: shuf invocation,  Next: uniq invocation,  Prev: sort invocation,  Up: Operating on sorted files

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 LINES'
`--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.  *Note Random sources::.

`-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

These 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.

   An exit status of zero indicates success, and a nonzero value
indicates failure.