Colorized grep -- viewing the entire file with highlighted matches

Question

I find grep s --color always flag to be tremendously useful  However  grep only prints lines with matches  unless you ask for context lines   Given that each line it prints has a match  the highlighting doesn t add as much capability as it could   I d really like to cat a file and see the entire file with the pattern matches highlighted   Is there some way I can tell grep to print every line being read regardless of whether there s a match  I know I could write a script to run grep on every line of a file  but I was curious whether this was possible with standard grep

User · Answer

If you want highlight several patterns with different colors see this bash script.

Basic usage:

echo warn error debug info 10 nil | colog

You can change patterns and colors while running pressing one key and then enter key.

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I d like to recommend ack -- better than grep  a power search tool for programmers      ack --color --passthru --pager    PAGER -less -R   pattern files      ack --color --passthru pattern files   less -R      export ACK PAGER COLOR    PAGER -less -R     ack --passthru pattern files   I love it because it defaults to recursive searching of directories  and does so much smarter than grep -r   supports full Perl regular expressions  rather than the POSIXish regex 3    and has a much nicer context display when searching many files

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It might seem like a dirty hack  grep  quot    highlight1  highlight2  highlight3 quot  filename  Which means - match the beginning of the line    or highlight1 or highlight2 or highlight3  As a result  you will get highlighted all highlight  pattern matches  even in the same line

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The -z option for grep is also pretty slick   cat file1   grep -z  pattern

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Here s my approach  inspired by  kepkin s solution     Adds ANSI colors to matched terms  similar to grep --color but without   filtering unmatched lines  Example      noisy command   highlight ERROR INFO     Each argument is passed into sed as a matching pattern and matches are   colored  Multiple arguments will use separate colors      Inspired by https   stackoverflow com a 25357856 highlight         color cycles from 0-5   shifted 31-36   i e  r g y b m c   local color 0 patterns      for term in       do     patterns      printf  s  s  e  sm  0 e 0m g     term               color 31            color      color 1    6      done   sed -f  lt  printf   s n     patterns           This accepts multiple arguments  but doesn t let you customize the colors   Example     noisy command   highlight ERROR WARN

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Ok  this is one way   wc -l filename   will give you the line count -- say NN  then you can do  grep -C NN --color always filename

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Here is a shell script that uses Awk s gsub function to replace the text you re searching for with the proper escape sequence to display it in bright red       bin bash awk -vstr  1  BEGIN repltext sprintf   c 1 31 40m amp  c 0m   0x1B 0x1B    gsub str repltext   print    2   Use it like so       cgrep pattern  file    Unfortunately  it doesn t have all the functionality of grep   For more information   you can refer to an article  So You Like Color  in Linux Journal

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You can also create an alias  Add this function in your  bashrc  or  bash profile on osx   function grepe       grep --color -E   1     2     You can now use the alias like this   ifconfig   grepe inet  or  grepe css index html     PS  don t forget to source    bashrc to reload bashrc on current session

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You can use my highlight script from https   github com kepkin dev-shell-essentials  It s better than grep because you can highlight each match with its own color     command here   highlight green  input    highlight red  output

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Alternatively you can use The Silver Searcher and do  ag  lt search gt  --passthrough

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To highlight patterns while viewing the whole file  h can do this   Plus it uses different colors for different patterns   cat FILE   h  PAT1   PAT2        You can also pipe the output of h to less -R for better reading   To grep and use 1 color for each pattern  cxpgrep could be a good fit

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I use rcg from  Linux Server Hacks   O Reilly   It s perfect for what you want and can highlight multiple expressions each with different colours      usr bin perl -w           regexp coloured glasses - from Linux Server Hacks from O Reilly           eg  rcg  fatal   BOLD   YELLOW   ON WHITE    var adm messages   use strict  use Term  ANSIColor qw  constants    my  target         while  my  arg   shift            my  clr   shift           if    arg      -       clr                    print  Usage  rcg  regex   color   regex   color      n                   exit 2                                  Ugly  lazy  pathetic hack here   Unquote                     target  arg    eval  clr       my  rst   RESET   while  lt  gt             foreach my  x  keys  target                     s   x   target  x  1 rst g                    print

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I added this to my  bash aliases   highlight       grep --color -E   1

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Here are some ways to do it  grep --color  pattern     file grep --color -E  pattern    file egrep --color  pattern    file  The   symbol is the OR operator  Either escape it using   or tell grep that the search text has to be interpreted as regular expressions by adding -E or using the egrep command instead of grep  The search text  quot pattern   quot  is actually a trick  it will match lines that have pattern OR lines that have an end  Because all lines have an end  all lines are matched  but the end of a line isn t actually any characters  so it won t be colored

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another dirty way   grep -A80 -B80 --color FIND THIS IN FILE   I did an  alias grepa  grep -A80 -B80 --color    in bashrc

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Here s something along the same lines  Chances are  you ll be using less anyway  so try this  less -p pattern file  It will highlight the pattern and jump to the first occurrence of it in the file  You can jump to the next occurence with n and to the previous occurence with p  Quit with q

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One other answer mentioned grep s -Cn switch which includes n lines of Context   I sometimes do this with n 99 as a quick-and-dirty way of getting  at least  a screenfull of context when the egrep pattern seems too fiddly  or when I m on a machine on which I ve not installed rcg and or ccze   I recently discovered ccze which is a more powerful colorizer   My only complaint is that it is screen-oriented  like less  which I never use for that reason  unless you specify the -A switch for  raw ANSI  output    1 for the rcg mention above   It is still my favorite since it is so simple to customize in an alias   Something like this is usually in my    bashrc   alias tailc  tail -f  my app log file   rcg send  BOLD GREEN  receive  CYAN  error  RED

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Is there some way I can tell grep to print every line being read   regardless of whether there s a match    Option -C999 will do the trick in the absence of an option to display all context lines  Most other grep variants support this too  However  1  no output is produced when no match is found and 2  this option has a negative impact on grep s efficiency  when the -C value is large this many lines may have to be temporarily stored in memory for grep to determine which lines of context to display when a match occurs  Note that grep implementations do not load input files but rather reads a few lines or use a sliding window over the input  The  before part  of the context has to be kept in a window  memory  to output the  before  context lines later when a match is found   A pattern such as   PATTERN or PATTERN   or any empty-matching sub-pattern for that matter such as    -    PATTERN is a nice trick  However  1  these patterns don t show non-matching lines highlighted as context and 2  this can t be used in combination with some other grep options  such as -F and -w for example   So none of these approaches are satisfying to me  I m using ugrep  and enhanced grep with option -y to efficiently display all non-matching output as color-highlighted context lines  Other grep-like tools such as ag and ripgrep also offer a pass-through option  But ugrep is compatible with GNU BSD grep and offers a superset of grep options like -y and -Q  For example  here is what option -y shows when combined with -Q  interactive query UI to enter patterns    ugrep -Q -y FILE

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Use ripgrep  aka rg  https   github com BurntSushi ripgrep rg --passthru    Color is the default     rg -t tf -e   key  tfstate  -e dynamodb table        --passthru        Print both matching and non-matching lines          Another way to achieve a similar effect is by modifying your pattern to        match the empty string          For example  if you are searching using rg foo then using         rg  quot   foo quot  instead will emit every line in every file searched  but only        occurrences of foo will be highlighted          This flag enables the same behavior without needing to modify the pattern   Sacrilege  granted  but grep has gotten complacent  brew apt rpm whatever install ripgrep You ll never go back

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Use colout program  http   nojhan github io colout   It is designed to add color highlights to a text stream  Given a regex and a color  e g   red    it reproduces a text stream with matches highlighted  e g     cat logfile but highlight instances of  ERROR  in red colout ERROR red  lt logfile   You can chain multiple invocations to add multiple different color highlights   tail -f  var log nginx access log         colout   5 d d   red         colout   4 d d   yellow         colout   3 d d   cyan         colout   2 d d   green   Or you can achieve the same thing by using a regex with N groups  parenthesised parts of the regex   followed by a comma separated list of N colors   vagrant status         colout                     running      suspended      not running                green yellow red

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As grep -E   pattern  has already been suggested  just wanted to clarify it s possible to highlight the whole line too  For example tail -f  somelog   grep --color -E      2

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I use following command for similar purpose   grep -C 100 searchtext file   This will say grep to print 100   2 lines of context  before  amp  after of the highlighted search text

[bash] Colorized grep -- viewing the entire file with highlighted matches

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