egrep

GREP(1)                          User Commands                         GREP(1)



NAME
       grep, egrep, fgrep - print lines that match patterns

SYNOPSIS
       grep [OPTION...] PATTERNS [FILE...]
       grep [OPTION...] -e PATTERNS ... [FILE...]
       grep [OPTION...] -f PATTERN_FILE ... [FILE...]

DESCRIPTION
       grep searches for PATTERNS in each FILE.  PATTERNS is one or patterns
       separated by newline characters, and grep prints each line that matches
       a pattern.

       A FILE of “-” stands for standard input.  If no FILE is given,
       recursive searches examine the working directory, and nonrecursive
       searches read standard input.

       In addition, the variant programs egrep and fgrep are the same as
       grep -E and grep -F, respectively.  These variants are deprecated, but
       are provided for backward compatibility.

OPTIONS
   Generic Program Information
       --help Output a usage message and exit.

       -V, --version
              Output the version number of grep and exit.

   Matcher Selection
       -E, --extended-regexp
              Interpret PATTERNS as extended regular expressions (EREs, see
              below).

       -F, --fixed-strings
              Interpret PATTERNS as fixed strings, not regular expressions.

       -G, --basic-regexp
              Interpret PATTERNS as basic regular expressions (BREs, see
              below).  This is the default.

       -P, --perl-regexp
              Interpret PATTERNS as Perl-compatible regular expressions
              (PCREs).  This option is experimental when combined with the -z
              (--null-data) option, and grep -P may warn of unimplemented
              features.

   Matching Control
       -e PATTERNS, --regexp=PATTERNS
              Use PATTERNS as the patterns.  If this option is used multiple
              times or is combined with the -f (--file) option, search for all
              patterns given.  This option can be used to protect a pattern
              beginning with “-”.

       -f FILE, --file=FILE
              Obtain patterns from FILE, one per line.  If this option is used
              multiple times or is combined with the -e (--regexp) option,
              search for all patterns given.  The empty file contains zero
              patterns, and therefore matches nothing.

       -i, --ignore-case
              Ignore case distinctions, so that characters that differ only in
              case match each other.

       -v, --invert-match
              Invert the sense of matching, to select non-matching lines.

       -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.  This option has no effect if -x is also specified.

       -x, --line-regexp
              Select only those matches that exactly match the whole line.
              For a regular expression pattern, this is like parenthesizing
              the pattern and then surrounding it with ^ and $.

       -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.

       --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.

       -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.

       -s, --no-messages
              Suppress error messages about nonexistent or unreadable files.

   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.

       -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 a file's data or metadata indicate that the file contains
              binary data, assume that the file is of type TYPE.  Non-text
              bytes indicate binary data; these are either output bytes that
              are improperly encoded for the current locale, or null input
              bytes when the -z option is not given.

              By default, TYPE is binary, and when grep discovers that a file
              is binary it suppresses any further output, and instead 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, when grep discovers that a file is
              binary it assumes that the rest of the 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.

              When type is binary, grep may treat non-text bytes as line
              terminators even without the -z option.  This means choosing
              binary versus text can affect whether a pattern matches a file.
              For example, when type is binary the pattern q$ might match q
              immediately followed by a null byte, even though this is not
              matched when type is text.  Conversely, when type is binary the
              pattern . (period) might not match a null byte.

              Warning: The -a option 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.  On the other
              hand, when reading files whose text encodings are unknown, it
              can be helpful to use -a or to set LC_ALL='C' in the
              environment, in order to find more matches even if the matches
              are unsafe for direct display.

       -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, i.e., read directories just as if they
              were ordinary files.  If ACTION is skip, silently skip
              directories.  If ACTION is recurse, read all files under each
              directory, recursively, following symbolic links only if they
              are on the command line.  This is equivalent to the -r option.

       --exclude=GLOB
              Skip any command-line file with a name suffix that matches the
              pattern GLOB, using wildcard matching; a name suffix is either
              the whole name, or any suffix starting after a / and before a
              non-/.  When searching recursively, skip any subfile whose base
              name matches GLOB; the base name is the part after the last /.
              A pattern 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=GLOB
              Skip any command-line directory with a name suffix that matches
              the pattern GLOB.  When searching recursively, skip any
              subdirectory whose base name matches GLOB.  Ignore any redundant
              trailing slashes in GLOB.

       -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, --recursive
              Read all files under each directory, recursively, following
              symbolic links only if they are on the command line.  Note that
              if no file operand is given, grep searches the working
              directory.  This is equivalent to the -d recurse option.

       -R, --dereference-recursive
              Read all files under each directory, recursively.  Follow all
              symbolic links, unlike -r.

   Other Options
       --line-buffered
              Use line buffering on output.  This can cause a performance
              penalty.

       -U, --binary
              Treat the file(s) as binary.  By default, under MS-DOS and MS-
              Windows, grep guesses whether a file is text or binary as
              described for the --binary-files option.  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 input and output data as sequences 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.

REGULAR EXPRESSIONS
       A regular expression is a pattern that describes a set of strings.
       Regular expressions are constructed analogously to arithmetic
       expressions, by using various operators to combine smaller expressions.

       grep understands three different versions of regular expression syntax:
       “basic” (BRE), “extended” (ERE) and “perl” (PCRE).  In GNU grep there
       is no difference in available functionality between basic and extended
       syntaxes.  In other implementations, basic regular expressions are less
       powerful.  The following description applies to extended regular
       expressions; differences for basic regular expressions are summarized
       afterwards.  Perl-compatible regular expressions give additional
       functionality, and are documented in pcresyntax(3) and pcrepattern(3),
       but work only if PCRE is available in the system.

       The fundamental building blocks are the regular expressions that match
       a single character.  Most characters, including all letters and digits,
       are regular expressions that match themselves.  Any meta-character with
       special meaning may be quoted by preceding it with a backslash.

       The period . matches any single character.  It is unspecified whether
       it matches an encoding error.

   Character Classes and Bracket Expressions
       A bracket expression is a list of characters enclosed by [ and ].  It
       matches any single character in that list.  If the first character of
       the list is the caret ^ then it matches any character not in the list;
       it is unspecified whether it matches an encoding error.  For example,
       the regular expression [0123456789] matches any single digit.

       Within a bracket expression, a range expression consists of two
       characters separated by a hyphen.  It matches any single character that
       sorts between the two characters, inclusive, using the locale's
       collating sequence and character set.  For example, in the default C
       locale, [a-d] is equivalent to [abcd].  Many locales sort characters in
       dictionary order, and in these locales [a-d] is typically not
       equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example.
       To obtain the traditional interpretation of bracket expressions, you
       can use the C locale by setting the LC_ALL environment variable to the
       value C.

       Finally, certain named classes of characters are predefined within
       bracket expressions, as follows.  Their names are self explanatory, and
       they are [:alnum:], [:alpha:], [:cntrl:], [:digit:], [:graph:],
       [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:].
       For example, [[:alnum:]] means the character class of numbers and
       letters in the current locale.  In the C locale and ASCII character set
       encoding, this is the same as [0-9A-Za-z].  (Note that the brackets in
       these class names are part of the symbolic names, and must be included
       in addition to the brackets delimiting the bracket expression.)  Most
       meta-characters lose their special meaning inside bracket expressions.
       To include a literal ] place it first in the list.  Similarly, to
       include a literal ^ place it anywhere but first.  Finally, to include a
       literal - place it last.

   Anchoring
       The caret ^ and the dollar sign $ are meta-characters that respectively
       match the empty string at the beginning and end of a line.

   The Backslash Character and Special Expressions
       The symbols \< and \> respectively match the empty string at the
       beginning and end of a word.  The symbol \b matches the empty string at
       the edge of a word, and \B matches the empty string provided it's not
       at the edge of a word.  The symbol \w is a synonym for [_[:alnum:]] and
       \W is a synonym for [^_[:alnum:]].

   Repetition
       A regular expression may be followed by one of several repetition
       operators:
       ?      The preceding item is optional and matched at most once.
       *      The preceding item will be matched zero or more times.
       +      The preceding item will be matched one or more times.
       {n}    The preceding item is matched exactly n times.
       {n,}   The preceding item is matched n or more times.
       {,m}   The preceding item is matched at most m times.  This is a GNU
              extension.
       {n,m}  The preceding item is matched at least n times, but not more
              than m times.

   Concatenation
       Two regular expressions may be concatenated; the resulting regular
       expression matches any string formed by concatenating two substrings
       that respectively match the concatenated expressions.

   Alternation
       Two regular expressions may be joined by the infix operator |; the
       resulting regular expression matches any string matching either
       alternate expression.

   Precedence
       Repetition takes precedence over concatenation, which in turn takes
       precedence over alternation.  A whole expression may be enclosed in
       parentheses to override these precedence rules and form a
       subexpression.

   Back References and Subexpressions
       The back-reference \n, where n is a single digit, matches the substring
       previously matched by the nth parenthesized subexpression of the
       regular expression.

   Basic vs Extended Regular Expressions
       In basic regular expressions the meta-characters ?, +, {, |, (, and )
       lose their special meaning; instead use the backslashed versions \?,
       \+, \{, \|, \(, and \).

ENVIRONMENT VARIABLES
       The behavior of grep is affected by the following environment
       variables.

       The locale for category LC_foo is specified by examining the three
       environment variables LC_ALL, LC_foo, LANG, in that order.  The first
       of these variables that is set specifies the locale.  For example, if
       LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian
       Portuguese locale is used for the LC_MESSAGES category.  The C locale
       is used if none of these environment variables are set, if the locale
       catalog is not installed, or if grep was not compiled with national
       language support (NLS).  The shell command locale -a lists locales that
       are currently available.

       GREP_OPTIONS
              This variable specifies default options to be placed in front of
              any explicit options.  As this causes problems when writing
              portable scripts, this feature will be removed in a future
              release of grep, and grep warns if it is used.  Please use an
              alias or script instead.

       GREP_COLOR
              This variable specifies the color used to highlight matched
              (non-empty) text.  It is deprecated in favor of GREP_COLORS, but
              still supported.  The mt, ms, and mc capabilities of GREP_COLORS
              have priority over it.  It can only specify the color used to
              highlight the matching non-empty text in any matching line (a
              selected line when the -v command-line option is omitted, or a
              context line when -v is specified).  The default is 01;31, which
              means a bold red foreground text on the terminal's default
              background.

       GREP_COLORS
              Specifies the colors and other attributes used to highlight
              various parts of the output.  Its value is a colon-separated
              list of capabilities that defaults to
              ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv
              and ne boolean capabilities omitted (i.e., false).  Supported
              capabilities are as follows.

              sl=    SGR substring for whole selected lines (i.e., matching
                     lines when the -v command-line option is omitted, or non-
                     matching lines when -v is specified).  If however the
                     boolean rv capability and the -v command-line option are
                     both specified, it applies to context matching lines
                     instead.  The default is empty (i.e., the terminal's
                     default color pair).

              cx=    SGR substring for whole context lines (i.e., non-matching
                     lines when the -v command-line option is omitted, or
                     matching lines when -v is specified).  If however the
                     boolean rv capability and the -v command-line option are
                     both specified, it applies to selected non-matching lines
                     instead.  The default is empty (i.e., the terminal's
                     default color pair).

              rv     Boolean value that reverses (swaps) the meanings of the
                     sl= and cx= capabilities when the -v command-line option
                     is specified.  The default is false (i.e., the capability
                     is omitted).

              mt=01;31
                     SGR substring for matching non-empty text in any matching
                     line (i.e., a selected line when the -v command-line
                     option is omitted, or a context line when -v is
                     specified).  Setting this is equivalent to setting both
                     ms= and mc= at once to the same value.  The default is a
                     bold red text foreground over the current line
                     background.

              ms=01;31
                     SGR substring for matching non-empty text in a selected
                     line.  (This is only used when the -v command-line option
                     is omitted.)  The effect of the sl= (or cx= if rv)
                     capability remains active when this kicks in.  The
                     default is a bold red text foreground over the current
                     line background.

              mc=01;31
                     SGR substring for matching non-empty text in a context
                     line.  (This is only used when the -v command-line option
                     is specified.)  The effect of the cx= (or sl= if rv)
                     capability remains active when this kicks in.  The
                     default is a bold red text foreground over the current
                     line background.

              fn=35  SGR substring for file names prefixing any content line.
                     The default is a magenta text foreground over the
                     terminal's default background.

              ln=32  SGR substring for line numbers prefixing any content
                     line.  The default is a green text foreground over the
                     terminal's default background.

              bn=32  SGR substring for byte offsets prefixing any content
                     line.  The default is a green text foreground over the
                     terminal's default background.

              se=36  SGR substring for separators that are inserted between
                     selected line fields (:), between context line fields,
                     (-), and between groups of adjacent lines when nonzero
                     context is specified (--).  The default is a cyan text
                     foreground over the terminal's default background.

              ne     Boolean value that prevents clearing to the end of line
                     using Erase in Line (EL) to Right (\33[K) each time a
                     colorized item ends.  This is needed on terminals on
                     which EL is not supported.  It is otherwise useful on
                     terminals for which the back_color_erase (bce) boolean
                     terminfo capability does not apply, when the chosen
                     highlight colors do not affect the background, or when EL
                     is too slow or causes too much flicker.  The default is
                     false (i.e., the capability is omitted).

              Note that boolean capabilities have no =... part.  They are
              omitted (i.e., false) by default and become true when specified.

              See the Select Graphic Rendition (SGR) section in the
              documentation of the text terminal that is used for permitted
              values and their meaning as character attributes.  These
              substring values are integers in decimal representation and can
              be concatenated with semicolons.  grep takes care of assembling
              the result into a complete SGR sequence (\33[...m).  Common
              values to concatenate include 1 for bold, 4 for underline, 5 for
              blink, 7 for inverse, 39 for default foreground color, 30 to 37
              for foreground colors, 90 to 97 for 16-color mode foreground
              colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes
              foreground colors, 49 for default background color, 40 to 47 for
              background colors, 100 to 107 for 16-color mode background
              colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes
              background colors.

       LC_ALL, LC_COLLATE, LANG
              These variables specify the locale for the LC_COLLATE category,
              which determines the collating sequence used to interpret range
              expressions like [a-z].

       LC_ALL, LC_CTYPE, LANG
              These variables specify the locale for the LC_CTYPE category,
              which determines the type of characters, e.g., which characters
              are whitespace.  This category also determines the character
              encoding, that is, whether text is encoded in UTF-8, ASCII, or
              some other encoding.  In the C or POSIX locale, all characters
              are encoded as a single byte and every byte is a valid
              character.

       LC_ALL, LC_MESSAGES, LANG
              These variables specify the locale for the LC_MESSAGES category,
              which determines the language that grep uses for messages.  The
              default C locale uses American English messages.

       POSIXLY_CORRECT
              If set, grep behaves as POSIX requires; otherwise, grep behaves
              more like other GNU programs.  POSIX requires that options that
              follow file names must be treated as file names; by default,
              such options are permuted to the front of the operand list and
              are treated as options.  Also, POSIX requires that unrecognized
              options be diagnosed as “illegal”, but since they are not really
              against the law the default is to diagnose them as “invalid”.
              POSIXLY_CORRECT also disables _N_GNU_nonoption_argv_flags_,
              described below.

       _N_GNU_nonoption_argv_flags_
              (Here N is grep's numeric process ID.)  If the ith character of
              this environment variable's value is 1, do not consider the ith
              operand of grep to be an option, even if it appears to be one.
              A shell can put this variable in the environment for each
              command it runs, specifying which operands are the results of
              file name wildcard expansion and therefore should not be treated
              as options.  This behavior is available only with the GNU C
              library, and only when POSIXLY_CORRECT is not set.

EXIT STATUS
       Normally the exit status is 0 if a line is selected, 1 if no lines were
       selected, and 2 if an error occurred.  However, if the -q or --quiet or
       --silent is used and a line is selected, the exit status is 0 even if
       an error occurred.

COPYRIGHT
       Copyright 1998–2000, 2002, 2005–2018 Free Software Foundation, Inc.

       This is free software; see the source for copying conditions.  There is
       NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
       PURPOSE.

BUGS
   Reporting Bugs
       Email bug reports to the bug-reporting address ⟨bug-grep@gnu.org⟩.  An
       email archive ⟨https://lists.gnu.org/mailman/listinfo/bug-grep⟩ and a
       bug tracker ⟨https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep⟩
       are available.

   Known Bugs
       Large repetition counts in the {n,m} construct may cause grep to use
       lots of memory.  In addition, certain other obscure regular expressions
       require exponential time and space, and may cause grep to run out of
       memory.

       Back-references are very slow, and may require exponential time.

SEE ALSO
   Regular Manual Pages
       awk(1), cmp(1), diff(1), find(1), gzip(1), perl(1), sed(1), sort(1),
       xargs(1), zgrep(1), read(2), pcre(3), pcresyntax(3), pcrepattern(3),
       terminfo(5), glob(7), regex(7).

   POSIX Programmer's Manual Page
       grep(1p).

   Full Documentation
       A complete manual ⟨https://www.gnu.org/software/grep/manual/⟩ is
       available.  If the info and grep programs are properly installed at
       your site, the command

              info grep

       should give you access to the complete manual.

NOTES
       This man page is maintained only fitfully; the full documentation is
       often more up-to-date.




GNU grep 3.3                      2018-05-11                           GREP(1)