GREP_COLORS – change the colors in the GREP output.

Today we will look at the variable GREP_COLORS. This variable determines the colour that is used with the grep command. You can look at the man page of the grep command to see what the various options mean. Here is the excerpt from the man command:

    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).

Now time for some examples:

1) With GREP_OPTIONS set to “”

1
export GREP_OPTIONS=

 

grep color options
grep color options

2) with the following set:

1
export GREP_COLORS="fn=34:mc=01;30:ms=33:sl=21:cx=31"

 

grep color options
grep color options

3) and just the colour for filename and match:

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export GREP_COLORS="mc=00;36:ms=31:mt=01;38"

 

grep color options
grep color options

4) Slightly lighter colour:

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export GREP_COLORS="mc=00;36:ms=31:mt=01;33"

 

grep color options
grep color options

5) Default colour for line numbers:

 

grep color options
grep color options

6) Line number colour:

1
export GREP_COLORS="mc=00;36:ms=31:mt=01;38:ln=31"

 

grep color options
grep color options

Hope you will put some colour to grep.

 

22/Apr/2019 : Edit – There is one more very useful article that you should check out – https://www.jenreviews.com/color-meaning/

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Delete all but some directories

I think, like me, you would have faced a lot of situations, where you wanted to delete all the files or directories in a location, leaving only the required files/directories. So, I have a directory containing lots of files/directories and I want to delete most of them except some 5/10 of them, how to I do it.

I finally wrote a small script to do that. First save list of files that you do not want to delete in file called “listnames” and then execute the below script. This will give you the rm commands that you need to execute. If you want you can execute the rm command from the script, but to be able to review, I just have the commands echoed.

#!/bin/bash -
#===============================================================================
#
#          FILE: del_all_logs.sh
#
#         USAGE: ./del_all_logs.sh
#
#   DESCRIPTION:
#
#       OPTIONS: ---
#  REQUIREMENTS: ---
#          BUGS: ---
#         NOTES: ---
#        AUTHOR: Amit Agarwal (aka)
#      REVISION:  ---
#===============================================================================

all_runs=$(echo *)
while read line
do
    all_runs=$(echo $all_runs |sed 's/'"$line"'//')
done 
all_runs=$(echo $all_runs |sed 's/'"$0"'//')
all_runs=$(echo $all_runs |sed 's/'"listnames"'//')
echo rm -rf $all_runs


 

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cksum – compare for multiple files.

If you have to compare cksum for couple of files, the you know how cumbersome it is. So, I wrote a simple script, wherein you can create a file called cksums in the current directory and copy paste the result of  “cksums *”  into this file, and then run this script. Cool 🙂

#!/bin/bash -
#===============================================================================
#
#          FILE: checkcksums.sh
#
#         USAGE: ./checkcksums.sh
#
#   DESCRIPTION: Compare cksums of multiple files.
#
#       OPTIONS: ---
#  REQUIREMENTS: ---
#          BUGS: ---
#         NOTES: ---
#        AUTHOR: Amit Agarwal (),
#  ORGANIZATION:
#       CREATED: 02/22/2013 09:12:17 PM IST
#      REVISION:  ---
#===============================================================================

file=cksums
while read line
do
    a=( $(echo $line) )
    if [[ -f ${a[2]} ]]
    then
        b=( $(cksum ${a[2]}) )
        if [[ $a == $b ]]
        then
            echo "Cksum for ${a[2]} = ${a[0]} matches"
        else
            echo "Failed ::Cksum for ${a[2]} = ${a[0]} matches"
        fi
    else
        echo "Failed :: file ${a[2]} does not exist"
    fi
done < $file
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