print lines matching a pattern

--color[=WHEN], --colour[=WHEN]
       Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers,
       byte offsets, and separators (for fields and groups of context lines)  with  escape  sequences  to
       display  them  in  color  on  the  terminal.   The  colors are defined by the environment variable
       GREP_COLORS.  The deprecated environment variable GREP_COLOR is still supported, but  its  setting
       does not have priority.  WHEN is never, always, or auto.

-m NUM, --max-count=NUM
       Stop reading a file after NUM matching lines.  If the input is standard input from a regular file,
       and NUM matching lines are output, grep ensures that the standard  input  is  positioned  to  just
       after the last matching line before exiting, regardless of the presence of trailing context lines.
       This enables a calling process to resume a search.  When grep stops after NUM matching  lines,  it
       outputs  any  trailing  context  lines.  When the -c or --count option is also used, grep does not
       output a count greater than NUM.  When the -v or --invert-match option is also  used,  grep  stops
       after outputting NUM non-matching lines.

Context Line Control
    -A NUM, --after-context=NUM
           Print NUM lines of trailing context after matching  lines.   Places  a  line  containing  a  group
           separator  (--) between contiguous groups of matches.  With the -o or --only-matching option, this
           has no effect and a warning is given.

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.

Before a command is executed, its input and output may be redirected using a special notation interpreted
by  the  shell.   Redirection  may  also  be used to open and close files for the current shell execution
environment.  The following redirection operators may precede or appear anywhere within a simple  command
or may follow a command.  Redirections are processed in the order they appear, from left to right.

Redirecting Output
    Redirection of output causes the file whose name results from the expansion of  word  to  be  opened  for
    writing  on  file descriptor n, or the standard output (file descriptor 1) if n is not specified.  If the
    file does not exist it is created; if it does exist it is truncated to zero size.

    The general format for redirecting output is:

           [n]>word

    If the redirection operator is >, and the noclobber option to the  set  builtin  has  been  enabled,  the
    redirection  will  fail if the file whose name results from the expansion of word exists and is a regular
    file.  If the redirection operator is >|, or the redirection operator is > and the  noclobber  option  to
    the  set  builtin  command  is  not  enabled, the redirection is attempted even if the file named by word
    exists.