NAME

shuf — print contents shuffled

SYNOPSIS

DESCRIPTION

In it's first form, shuf reads lines from each file or if unspecified or when file is "-", lines are read from standard input. And are then shuffled and printed using a reservoir shuffle, see SHUFFLING for details.

In it's second form, shuf uses a Fisher-Yates shuffle to swap-shuffle all the strings, and then prints them out as lines.

OPTIONS

-e

Use each string as an input line.

-n num

Output at most num lines.

-z

Use NULL as line delimiter, not newline.

SHUFFLING

In it's first form, shuf uses a reservoir of 512 lines. It picks a random location, prints a line if present, then inserts a newly read line. Once all lines are read it prints the lines still present in the reservoir.
While this isn't truly a random sort as lines beyond 512 won't be printed first, it allows to use a bounded amount of memory.

EXIT STATUS

The shuf utility exits 0 on success, and >0 if an error occurs.

SEE ALSO

sort(1)

HISTORY

An shuf utility appeared in GNU coreutils 6.0.

AUTHORS

Haelwenn (lanodan) Monnier <contact+utils@hacktivis.me>