Linux Ascendance Business Tutorial For Beginners 37 - Grep Command

GREP(1)               GREP(1)  NAME        grep,  egrep,  fgrep, zgrep, zegrep, zfgrep, bzgrep, bzegrep, bzfgrep -        impress lines matching a pattern  SYNOPSIS        grep [options] PATTERN [FILE...]        grep [options] [-e PATTERN | -f FILE] [FILE...]  DESCRIPTION        grep searches the named input FILEs (or measure input if no files  are        named, or the file cite - is given) for lines containing a jibe to the        given PATTERN.  By default, grep prints the matching lines.         In addition, 2 variant programs egrep in addition to fgrep are available.  egrep        is  the same  equally grep -E.  fgrep is the same equally grep -F.  zgrep is the        same equally grep -Z.  zegrep is the same equally grep -EZ.  zfgrep is  the  same        equally grep -FZ.  OPTIONS        -A NUM, --after-context=NUM        Print  NUM  lines  of  trailing  context after  matching lines.        Places  a  line of piece of job  containing  --  betwixt contiguous  groups  of        matches.         -a, --text        Process  a binary file equally if it were text; this is equivalent to        the --binary-files=text option.         -B NUM, --before-context=NUM        Print NUM  lines of  leading  context  earlier  matching lines.        Places  a  line of piece of job  containing  --  betwixt contiguous  groups  of        matches.         -C NUM, --context=NUM        Print NUM lines of output context.  Places a line of piece of job containing  --        betwixt contiguous groups of matches.         -b, --byte-offset        Print  the byte offset within the input file earlier each line of piece of job of        output.         --binary-files=TYPE        If the initiative of all few bytes of a file dot that the file contains        binary  data, assume that the file is of type TYPE.  By default,        TYPE is binary, in addition to grep commonly outputs either a one-line mes-        sage  maxim  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 non match; this is equivalent to the -I option.        If TYPE is text, grep processes a binary file  equally  if  it  were        text;  this  is  equivalent  to  the  -a option.  Warning: grep        --binary-files=text mightiness output binary garbage, which tin  have        nasty side effects if the output is a terminal in addition to if the termi-        nal driver interprets approximately of it equally commands.         --colour[=WHEN], --color[=WHEN]        Surround the matching string amongst the mark let on inwards  GREP_COLOR        surround variable. WHEN may live `never', `always', or `auto'         -c, --count        Suppress normal output; instead impress a count of matching lines        for each input file.  With the -v,  --invert-match  selection  (see        below), count non-matching lines.         -D ACTION, --devices=ACTION        If  an  input  file  is  a device, FIFO or socket, utilization ACTION to        procedure it.  By  default,  ACTION  is  read,  which  agency  that        devices are read simply equally if they were ordinary files.  If ACTION        is skip, devices are silently skipped.         -d ACTION, --directories=ACTION        If an input file is a directory, utilization ACTION to procedure  it.   By        default, ACTION is read, which agency that directories are read        simply equally if they were ordinary files.  If ACTION is skip, direc-        tories  are  silently skipped.  If ACTION is recurse, grep reads        all files nether each directory, recursively; this is  equivalent        to the -r option.         -E, --extended-regexp        Interpret PATTERN equally an extended regular appear (see below).         -e PATTERN, --regexp=PATTERN        Use PATTERN equally the pattern; useful to protect patterns beginning        amongst -.         -F, --fixed-strings        Interpret  PATTERN equally a listing of fixed strings, separated past times new-        lines, whatsoever of which is to live matched.         -P, --perl-regexp        Interpret PATTERN equally a Perl regular expression.  This selection  is        non supported inwards FreeBSD.         -f FILE, --file=FILE        Obtain  patterns from  FILE, ane per line.  The empty file con-        tains null patterns, in addition to hence matches nothing.         -G, --basic-regexp        Interpret PATTERN equally a basic  regular  appear  (see  below).        This is the default.         -H, --with-filename        Print the filename for each match.         -h, --no-filename        Suppress the  prefixing of  filenames  on output when multiple        files are searched.         --help Output a brief assistance message.         -I     Process a binary file equally if it did non  incorporate  matching  data;        this is equivalent to the --binary-files=without-match option.         -i, --ignore-case        Ignore  instance  distinctions  inwards  both  the  PATTERN in addition to the input        files.         -L, --files-without-match        Suppress normal output; instead impress the  cite  of  each  input        file from which no output would commonly possess got been printed.  The        scanning volition halt on the initiative of all match.         -l, --files-with-matches        Suppress normal output; instead impress the  cite  of  each  input        file  from  which  output would commonly possess got been printed.  The        scanning volition halt on the initiative of all match.         -m NUM, --max-count=NUM        Stop reading a file after NUM matching lines.  If the  input  is        measure input  from a regular file, in addition to NUM matching lines are        output, grep ensures that the measure input  is positioned  to        simply  after the terminal matching line of piece of job earlier exiting, regardless of        the presence of trailing context lines.  This enables a  calling        procedure  to resume a search.  When grep stops after NUM matching        lines, it outputs whatsoever trailing context lines.  When  the -c  or        --count  selection  is  also  used, grep  does  non output a count        greater than NUM.  When the -v or --invert-match selection is  also        used, grep stops after outputting NUM non-matching lines.         --mmap If  possible, utilization the mmap(2) organisation telephone telephone to read input, instead        of the default read(2) organisation call.  In approximately situations, --mmap        yields  ameliorate performance.  However, --mmap tin effort undefined        demeanour (including gist dumps) if an input file shrinks  while        grep is operating, or if an I/O fault occurs.         -n, --line-number        Prefix each line of piece of job of output amongst the line of piece of job seat out within its input        file.         -o, --only-matching        Show exclusively the percentage of a matching line of piece of job that matches PATTERN.         --label=LABEL        Displays input genuinely coming from measure input equally input com-        ing  from  file LABEL.  This is peculiarly useful for tools like        zgrep, e.g.  gzip -cd foo.gz |grep --label=foo something         --line-buffered        Flush output on every line.  Note that this incurs a performance        penalty.         -q, --quiet, --silent        Quiet;  practise  non write anything to measure output.  Exit immedi-        ately amongst null condition if whatsoever jibe is found, fifty-fifty if  an  error        was detected.  Also come across the -s or --no-messages option.         -R, -r, --recursive        Read all files nether each directory, recursively; this is equiv-        alent to the -d recurse option.    --include=PATTERN        Recurse inwards directories exclusively searching file matching PATTERN.    --exclude=PATTERN        Recurse inwards directories skip file matching PATTERN.         -s, --no-messages        Suppress fault messages most nonexistent or  unreadable files.        Portability note: dissimilar GNU grep, traditional grep did non con-        shape to POSIX.2, because traditional grep lacked a -q selection and        its  -s selection behaved similar GNU grep's -q option.  Shell scripts        intended to live portable to traditional grep should avoid both -q        in addition to -s in addition to should redirect output to /dev/null instead.         -U, --binary        Treat  the  file(s) equally binary.  By default, nether MS-DOS in addition to MS-        Windows, grep guesses the file type past times looking at  the  contents        of  the initiative of all 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  brand  regular expressions amongst ^ in addition to $ work        correctly).  Specifying -U overrules this guesswork, causing all        files  to live read in addition to passed to the matching machinery verbatim;        if the file is a text file amongst CR/LF pairs at the terminate  of  each        line,  this  volition  effort approximately regular expressions to fail.  This        selection has no outcome on platforms other than MS-DOS in addition to  MS-Win-        dows.         -u, --unix-byte-offsets        Report  Unix-style  byte offsets.   This  switch causes grep to        written report byte offsets equally if the file were  Unix-style  text  file,        i.e. amongst CR characters stripped off.  This volition make results        identical to running grep on a Unix machine.  This selection has no        outcome  unless -b selection is also used; it has no outcome on plat-        forms other than MS-DOS in addition to MS-Windows.         -V, --version        Print the version seat out of grep to measure error.   This  ver-        sion seat out should live included inwards all põrnikas reports (see below).         -v, --invert-match        Invert the feel of matching, to select non-matching lines.         -w, --word-regexp        Select  exclusively  those  lines  containing  matches  that shape whole        words.  The evidence is that the matching substring must  either  be        at  the  starting fourth dimension  of  the line, or preceded past times a non-word con-        stituent character.  Similarly, it must live either at the terminate  of        the line of piece of job or followed past times a non-word element character.  Word-        element characters are letters, digits, in addition to the  underscore.         -x, --line-regexp        Select exclusively those matches that precisely jibe the whole line.         -y     Obsolete synonym for -i.         --null Output  a  null  byte  (the  ASCII NUL character) instead of the        grapheme that commonly follows a file name.  For example,  grep        -l  --null  outputs  a null byte after each file cite instead of        the park newline.  This selection makes  the  output  unambiguous,        fifty-fifty inwards the presence of file names containing odd characters        similar newlines.  This selection tin live used amongst commands similar  find        -print0, perl  -0,  form  -z, in addition to xargs -0 to procedure arbitrary        file names, fifty-fifty those that incorporate newline characters.         -Z, --decompress        Decompress the input information earlier searching.  This selection is only        available if compiled amongst zlib(3) library.         -J, --bz2decompress        Decompress  the bzip2(1) compressed input information earlier searching.  REGULAR EXPRESSIONS        Influenza A virus subtype H5N1 regular appear is a designing that  describes  a  laid  of  strings.        Regular expressions  are constructed analogously to arithmetics expres-        sions, past times using diverse operators to combine smaller expressions.         grep understands 2 different versions of regular  appear  syntax:        "basic" in addition to "extended."  In GNU grep, at that topographic point is no departure inwards avail-        able functionality using  either  syntax.   In  other  implementations,        basic regular expressions are less powerful.  The next description        applies to extended regular expressions; differences for basic  regular        expressions are summarized afterwards.         The  cardinal edifice blocks are the regular expressions that match        a unmarried character.  Most characters, including all letters in addition to digits,        are  regular expressions that jibe themselves. Any metacharacter with        special pregnant may live quoted past times preceding it amongst a backslash.         Influenza A virus subtype H5N1 bracket appear is a listing of characters enclosed past times [ in addition to  ].   It        matches whatsoever  unmarried  grapheme inwards that list; if the initiative of all grapheme of        the listing is the caret ^ so it matches whatsoever grapheme non inwards the  list.        For  example,  the  regular  appear [0123456789] matches whatsoever single        digit.         Within a bracket expression, a attain appear consists of 2 charac-        ters separated past times a hyphen.  It matches whatsoever unmarried grapheme that sorts        betwixt the 2 characters, inclusive,  using  the  locale's  collating        sequence  in addition to  grapheme  set. For  example, inwards the default C locale,        [a-d] is equivalent to [abcd].  Many locales form characters inwards dictio-        nary  order,  in addition to inwards these locales [a-d] is typically non equivalent to        [abcd]; it mightiness live equivalent to [aBbCcDd], for  example.   To obtain        the  traditional interpretation of bracket expressions, you lot tin utilization the        C locale past times setting the LC_ALL surround variable to the value C.         Finally, certainly named classes  of  characters  are  predefined within        bracket expressions, equally follows.  Their names are self explanatory, and        they  are  [:alnum:],  [:alpha:],  [:blank:],   [:cntrl:],   [:digit:],        [:graph:],  [:lower:],  [:print:], [:punct:], [:space:], [:upper:], and        [:xdigit:].  For example, [[:alnum:]]  agency  [0-9A-Za-z],  except  the        latter shape depends upon the C locale in addition to the ASCII grapheme encoding,        whereas the quondam is independent of locale in addition to grapheme  set.  (Note        that  the brackets inwards these course of education names are percentage of the symbolic names,        in addition to must live included inwards add-on to the brackets delimiting the bracket        list.) Most  metacharacters  lose their special pregnant within lists.        To include a literal ] house it initiative of all  inwards  the list. Similarly,  to        include a literal ^ house it anywhere but first.  Finally, to include a        literal - house it last.         The menstruum .  matches whatsoever unmarried character.  The symbol \w is a synonym        for [[:alnum:]] in addition to \W is a synonym for [^[:alnum:]].         The  caret ^ in addition to the dollar sign $ are metacharacters that respectively        jibe the empty string at the starting fourth dimension in addition to terminate of a line.  The symbols        \<  in addition to \> respectively jibe the empty string at the starting fourth dimension in addition to end        of a word.  The symbol \b matches the empty string at  the  border  of  a        word,  in addition to \B matches the empty string provided it's non at the border of        a word.         Influenza A virus subtype H5N1 regular appear may live followed past times ane of several repetition oper-        ators:        ?      The preceding detail is optional in addition to matched at most once.        *      The preceding detail volition live matched null or to a greater extent than times.        +      The preceding detail volition live matched ane or to a greater extent than times.        {n}    The preceding detail is matched precisely n times.        {n,}   The preceding detail is matched n or to a greater extent than times.        {n,m}  The  preceding  detail  is matched at to the lowest degree n times, but non more        than thousand times.         Two regular expressions may  live concatenated;  the  resulting  regular        appear  matches  whatsoever  string formed past times concatenating 2 substrings        that respectively jibe the concatenated subexpressions.         Two regular expressions may live joined past times  the  infix  operator  |;  the        resulting  regular appear matches whatsoever string matching either subex-        pression.         Repetition takes precedence over concatenation, which  inwards  plow  takes        precedence  over alternation.  Influenza A virus subtype H5N1 whole subexpression may live enclosed in        parentheses to override these precedence rules.         The backreference \n, where n is a unmarried digit, matches the  substring        previously  matched past times the nth parenthesized subexpression of the regu-        lar expression.         In basic regular expressions the metacharacters ?, +, {, |,  (, in addition to  )        lose  their  special  meaning; instead utilization the backslashed versions \?,        \+, \{, \|, \(, in addition to \).         Traditional egrep did non back upwards the { metacharacter, in addition to  approximately  egrep        implementations back upwards \{ instead, so portable scripts should avoid {        inwards egrep patterns in addition to should utilization [{] to jibe a literal {.         GNU egrep attempts to back upwards traditional usage past times assuming that  {  is        non  special if it would live the start of an invalid interval specifica-        tion.  For example, the rhythm dominance egrep '{1' searches for the  two-        grapheme  string {1 instead of reporting a syntax fault inwards the regular        expression.  POSIX.2 allows this demeanour equally an extension, but portable        scripts should avoid it.  ENVIRONMENT VARIABLES        Grep's demeanour is affected past times the next surround variables.         Influenza A virus subtype H5N1  locale  LC_foo is specified past times examining the 3 surround vari-        ables LC_ALL, LC_foo, LANG, inwards that order.  The initiative of all  of  these  vari-        ables  that is laid specifies the locale.  For example, if LC_ALL is not        set, but LC_MESSAGES is laid to pt_BR, so Brazilian Portuguese is used        for  the  LC_MESSAGES  locale. The  C locale is used if none of these        surround variables  are  set,  or  if  the  locale  catalog  is  not        installed,  or  if grep was non compiled amongst national linguistic communication support        (NLS).         GREP_OPTIONS        This variable specifies default options to live placed inwards forepart of        whatsoever   explicit   options.    For example,  if  GREP_OPTIONS  is        '--binary-files=without-match --directories=skip', grep  behaves        equally  if the 2 options --binary-files=without-match in addition to --direc-        tories=skip had been  specified  earlier  whatsoever  explicit  options.        Option  specifications are separated past times whitespace.  Influenza A virus subtype H5N1 backslash        escapes the adjacent character, so it tin  live  used  to  specify  an        selection containing whitespace or a backslash.         GREP_COLOR        Specifies the mark for highlighting.         LC_ALL, LC_COLLATE, LANG        These  variables specify the LC_COLLATE locale, which determines        the collating sequence used to translate attain expressions  like        [a-z].         LC_ALL, LC_CTYPE, LANG        These  variables specify  the LC_CTYPE locale, which determines        the type of characters, e.g., which characters are whitespace.         LC_ALL, LC_MESSAGES, LANG        These variables specify the LC_MESSAGES locale, which determines        the  linguistic communication that grep uses for messages.  The default C locale        uses American English linguistic communication messages.         POSIXLY_CORRECT        If set,  grep  behaves  equally  POSIX.2  requires;  otherwise,  grep        behaves  to a greater extent than  similar  other  GNU programs.  POSIX.2 requires that        options that follow file names must live treated equally file names; by        default, such  options are permuted to the forepart of the operand        listing in addition to are treated equally options. Also,  POSIX.2 requires  that        unrecognized  options  live diagnosed equally "illegal", but since they        are non genuinely against the police trace the default is to diagnose  them        equally "invalid".  DIAGNOSTICS        Normally, locomote out condition is 0 if selected lines are constitute in addition to 1 otherwise.        But the locomote out condition is 2 if an fault occurred, unless the -q or --quiet        or --silent selection is used in addition to a selected line of piece of job is found.  BUGS        Email  põrnikas  reports  to bug-gnu-utils@gnu.org. Be certainly to include the        give-and-take "grep" somewhere inwards the "Subject:" field.         Large repetition counts inwards the {n,m} create may effort  grep  to  use        lots of memory. In addition, certainly other obscure regular expressions        take away exponential fourth dimension in addition to space, in addition to may effort grep to  run  out  of        memory.         Backreferences are really slow, in addition to may take away exponential time.  GNU Project     2002/01/22          GREP(1)