concatenate files and print on the standard output

-n, --number
       number all output lines

Concatenate FILE(s), or standard input, to standard output.

With no FILE, or when FILE is -, read standard input.

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).

print lines matching a pattern

Matcher Selection
    -E, --extended-regexp
           Interpret PATTERN as an extended regular expression (ERE, see below).  (-E is specified by POSIX.)

-o, --only-matching
       Print  only  the  matched  (non-empty) parts of a matching line, with each such part on a separate
       output line.

grep searches the named input FILEs (or standard input if no files are named, or if a single hyphen-minus
(-) is given as file name) for lines containing a match to the given PATTERN.  By  default,  grep  prints
the matching lines.

sort lines of text files

report or omit repeated lines

search a file for a pattern

-i     Perform  pattern  matching  in searches without regard to case; see the Base Definitions volume of
       IEEE Std 1003.1-2001, Section 9.2, Regular Expression General Requirements.

-c     Write only a count of selected lines to standard output.

-e  pattern_list

       Specify one or more patterns to be used during the search for input.  The application shall ensure
       that patterns in pattern_list are separated by a <newline>. A null pattern can be specified by two
       adjacent  <newline>s  in  pattern_list. Unless the -E or -F option is also specified, each pattern
       shall be treated as a BRE, as described in the Base Definitions  volume  of  IEEE Std 1003.1-2001,
       Section  9.3,  Basic Regular Expressions. Multiple -e and -f options shall be accepted by the grep
       utility. All of the specified patterns shall be  used  when  matching  lines,  but  the  order  of
       evaluation is unspecified.

-f  pattern_file

       Read  one  or  more  patterns  from  the  file  named  by  the pathname pattern_file.  Patterns in
       pattern_file shall be terminated by a <newline>. A null pattern can be specified by an empty  line
       in  pattern_file. Unless the -E or -F option is also specified, each pattern shall be treated as a
       BRE, as described in the Base Definitions  volume  of  IEEE Std 1003.1-2001,  Section  9.3,  Basic
       Regular Expressions.