search for files in a directory hierarchy

Pipelines
    A  pipeline is a sequence of one or more commands separated by one of the control operators | or |&.  The
    format for a pipeline is:

           [time [-p]] [ ! ] command [ [|⎪|&] command2 ... ]

    The standard output of command is connected  via  a  pipe  to  the  standard  input  of  command2.   This
    connection  is performed before any redirections specified by the command (see REDIRECTION below).  If |&
    is used, the standard error of command is connected to command2's standard input through the pipe; it  is
    shorthand  for  2>&1  |.   This  implicit  redirection  of  the  standard  error  is  performed after any
    redirections specified by the command.

    The return status of a pipeline is the exit status of the last command, unless  the  pipefail  option  is
    enabled.   If  pipefail  is  enabled,  the  pipeline's return status is the value of the last (rightmost)
    command to exit with a non-zero status, or zero if all commands exit successfully.  If the reserved  word
    !   precedes  a  pipeline, the exit status of that pipeline is the logical negation of the exit status as
    described above.  The shell waits for all commands in the pipeline to terminate before returning a value.

    If the time reserved word precedes a pipeline, the elapsed as well as user and system  time  consumed  by
    its execution are reported when the pipeline terminates.  The -p option changes the output format to that
    specified by POSIX.  When the shell is in posix mode, it does not recognize time as a  reserved  word  if
    the  next  token begins with a `-'.  The TIMEFORMAT variable may be set to a format string that specifies
    how the timing information should be displayed; see the description of TIMEFORMAT under  Shell  Variables
    below.

    When the shell is in posix mode, time may be followed by a newline.  In this case, the shell displays the
    total user and system time consumed by the shell and its children.  The TIMEFORMAT variable may  be  used
    to specify the format of the time information.

    Each command in a pipeline is executed as a separate process (i.e., in a subshell).

generate random permutations

-z, --zero-terminated
       end lines with 0 byte, not newline

copy the first part of files

-n  number
       The first number lines of each input file shall be copied  to  standard  output.  The  application
       shall ensure that the number option-argument is a positive decimal integer.

build and execute command lines from standard input

--null
-0     Input items are terminated by a null character instead  of  by  whitespace,  and  the  quotes  and
       backslash  are not special (every character is taken literally).  Disables the end of file string,
       which is treated like any other argument.  Useful when input  items  might  contain  white  space,
       quote marks, or backslashes.  The GNU find -print0 option produces input suitable for this mode.

--max-args=max-args
-n max-args
       Use at most max-args arguments per command line.  Fewer than max-args arguments will  be  used  if
       the  size (see the -s option) is exceeded, unless the -x option is given, in which case xargs will
       exit.

-I replace-str
       Replace occurrences of replace-str in the initial-arguments with names read from  standard  input.
       Also,  unquoted  blanks  do  not  terminate  input  items;  instead  the  separator is the newline
       character.  Implies -x and -L 1.

copy files and directories

Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY.