grep(1) - print lines matching a pattern
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.
Generic Program Information
    --help Print  a  usage  message  briefly  summarizing  these  command-line  options and the bug-reporting
           address, then exit.
-V, --version
       Print the version number of grep to the standard output stream.  This  version  number  should  be
       included in all bug reports (see below).
Matcher Selection
    -E, --extended-regexp
           Interpret PATTERN as an extended regular expression (ERE, see below).  (-E is specified by POSIX.)
-F, --fixed-strings
       Interpret  PATTERN  as  a  list  of  fixed  strings,  separated by newlines, any of which is to be
       matched.  (-F is specified by POSIX.)
-G, --basic-regexp
       Interpret PATTERN as a basic regular expression (BRE, see below).  This is the default.
-P, --perl-regexp
       Interpret PATTERN as a Perl regular expression (PCRE, see below).  This is highly experimental and
       grep -P may warn of unimplemented features.
Matching Control
    -e PATTERN, --regexp=PATTERN
           Use PATTERN as the pattern.  This can be used to specify multiple search patterns, or to protect a
           pattern beginning with a hyphen (-).  (-e is specified by POSIX.)
-f FILE, --file=FILE
       Obtain patterns from FILE, one per line.  The empty file contains  zero  patterns,  and  therefore
       matches nothing.  (-f is specified by POSIX.)
-i, --ignore-case
       Ignore case distinctions in both the PATTERN and the input files.  (-i is specified by POSIX.)
-v, --invert-match
       Invert the sense of matching, to select non-matching lines.  (-v is specified by POSIX.)
-w, --word-regexp
       Select  only  those lines containing matches that form whole words.  The test is that the matching
       substring must either be at the beginning of the line,  or  preceded  by  a  non-word  constituent
       character.   Similarly,  it  must  be  either  at  the  end  of the line or followed by a non-word
       constituent character.  Word-constituent characters are letters, digits, and the underscore.
-x, --line-regexp
       Select only those matches that exactly match the whole line.  (-x is specified by POSIX.)
-y     Obsolete synonym for -i.
General Output Control
    -c, --count
           Suppress normal output; instead print a count of matching lines for each input file.  With the -v,
           --invert-match option (see below), count non-matching lines.  (-c is specified by POSIX.)
--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.
-L, --files-without-match
       Suppress  normal  output;  instead  print  the  name of each input file from which no output would
       normally have been printed.  The scanning will stop on the first match.
-l, --files-with-matches
       Suppress normal output; instead print the name of each input file from which output would normally
       have been printed.  The scanning will stop on the first match.  (-l is specified by POSIX.)
-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.
-o, --only-matching
       Print  only  the  matched  (non-empty) parts of a matching line, with each such part on a separate
       output line.
-q, --quiet, --silent
       Quiet; do not write anything to standard output.  Exit immediately with zero status if  any  match
       is  found,  even  if  an  error  was  detected.   Also see the -s or --no-messages option.  (-q is
       specified by POSIX.)
-s, --no-messages
       Suppress error messages about nonexistent or unreadable files.  Portability note: unlike GNU grep,
       7th  Edition  Unix  grep  did not conform to POSIX, because it lacked -q and its -s option behaved
       like GNU grep's -q option.  USG-style grep also lacked -q but its -s option behaved like GNU grep.
       Portable  shell  scripts should avoid both -q and -s and should redirect standard and error output
       to /dev/null instead.  (-s is specified by POSIX.)
Output Line Prefix Control
    -b, --byte-offset
           Print the 0-based byte  offset  within  the  input  file  before  each  line  of  output.   If  -o
           (--only-matching) is specified, print the offset of the matching part itself.
-H, --with-filename
       Print  the  file  name  for  each  match.  This is the default when there is more than one file to
       search.
-h, --no-filename
       Suppress the prefixing of file names on output.  This is the default when there is only  one  file
       (or only standard input) to search.
--label=LABEL
       Display  input  actually  coming  from  standard  input  as input coming from file LABEL.  This is
       especially useful when implementing tools like zgrep, e.g., gzip -cd foo.gz | grep --label=foo  -H
       something.  See also the -H option.
-n, --line-number
       Prefix  each  line of output with the 1-based line number within its input file.  (-n is specified
       by POSIX.)
-T, --initial-tab
       Make sure that the first character of actual line  content  lies  on  a  tab  stop,  so  that  the
       alignment  of  tabs  looks  normal.   This  is useful with options that prefix their output to the
       actual content: -H,-n, and -b.  In order to improve the probability that lines from a single  file
       will  all  start at the same column, this also causes the line number and byte offset (if present)
       to be printed in a minimum size field width.
-u, --unix-byte-offsets
       Report Unix-style byte offsets.  This switch causes grep to report byte offsets  as  if  the  file
       were  a  Unix-style  text  file, i.e., with CR characters stripped off.  This will produce results
       identical to running grep on a Unix machine.  This option has no effect unless -b option  is  also
       used; it has no effect on platforms other than MS-DOS and MS-Windows.
-Z, --null
       Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file
       name.  For example, grep -lZ outputs a zero byte  after  each  file  name  instead  of  the  usual
       newline.   This option makes the output unambiguous, even in the presence of file names containing
       unusual characters like newlines.  This option can be used with commands like find  -print0,  perl
       -0,  sort  -z,  and  xargs  -0  to  process  arbitrary file names, even those that contain newline
       characters.
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.
-B NUM, --before-context=NUM
       Print NUM lines of leading context before 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.
-C NUM, -NUM, --context=NUM
       Print NUM lines of output context.  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.
File and Directory Selection
    -a, --text
           Process a binary file as if it were text; this is equivalent to the --binary-files=text option.
--binary-files=TYPE
       If the first few bytes of a file indicate that the file contains binary data, assume that the file
       is  of type TYPE.  By default, TYPE is binary, and grep normally outputs either a one-line message
       saying that a binary file matches, or no message if there is no match.  If TYPE is  without-match,
       grep  assumes  that a binary file does not match; this is equivalent to the -I option.  If TYPE is
       text, grep processes a binary file as if it were text;  this  is  equivalent  to  the  -a  option.
       Warning:  grep  --binary-files=text might output binary garbage, which can have nasty side effects
       if the output is a terminal and if the terminal driver interprets some of it as commands.
-D ACTION, --devices=ACTION
       If an input file is a device, FIFO or socket, use ACTION to process it.   By  default,  ACTION  is
       read,  which  means that devices are read just as if they were ordinary files.  If ACTION is skip,
       devices are silently skipped.
-d ACTION, --directories=ACTION
       If an input file is a directory, use ACTION to process it.  By  default,  ACTION  is  read,  which
       means  that  directories  are  read  just  as  if  they  were  ordinary files.  If ACTION is skip,
       directories are silently skipped.   If  ACTION  is  recurse,  grep  reads  all  files  under  each
       directory, recursively; this is equivalent to the -r option.
--exclude=GLOB
       Skip files whose base name matches GLOB (using wildcard matching).  A file-name glob can use *, ?,
       and [...]  as wildcards, and \ to quote a wildcard or backslash character literally.
--exclude-from=FILE
       Skip files whose base name matches any of the file-name  globs  read  from  FILE  (using  wildcard
       matching as described under --exclude).
--exclude-dir=DIR
       Exclude directories matching the pattern DIR from recursive searches.
-I     Process  a  binary  file  as  if  it  did  not  contain  matching  data; this is equivalent to the
       --binary-files=without-match option.
--include=GLOB
       Search only files whose base name  matches  GLOB  (using  wildcard  matching  as  described  under
       --exclude).
-R, -r, --recursive
       Read all files under each directory, recursively; this is equivalent to the -d recurse option.
Other Options
    --line-buffered
           Use line buffering on output.  This can cause a performance penalty.
--mmap If  possible,  use  the  mmap(2)  system call to read input, instead of the default read(2) system
       call.  In some situations, --mmap yields better performance.  However, --mmap can cause  undefined
       behavior  (including  core  dumps)  if an input file shrinks while grep is operating, or if an I/O
       error occurs.
-U, --binary
       Treat the file(s) as binary.  By default, under MS-DOS and MS-Windows, grep guesses the file  type
       by  looking  at  the contents of the first 32KB read from the file.  If grep decides the file is a
       text file, it strips  the  CR  characters  from  the  original  file  contents  (to  make  regular
       expressions  with  ^  and  $ work correctly).  Specifying -U overrules this guesswork, causing all
       files to be read and passed to the matching mechanism verbatim; if the file is a  text  file  with
       CR/LF  pairs  at  the  end  of  each line, this will cause some regular expressions to fail.  This
       option has no effect on platforms other than MS-DOS and MS-Windows.
-z, --null-data
       Treat the input as a set of lines, each terminated by  a  zero  byte  (the  ASCII  NUL  character)
       instead  of  a  newline.  Like the -Z or --null option, this option can be used with commands like
       sort -z to process arbitrary file names.