Bash commands

commands.sh

-r: recursive
-i: ignore case sensitive
-w: match the full words
-B: prints the specified N lines before the match
-A: prints the specified N lines after the match
-C: shows N lines in both the side(before & after) of match

grep -r h[1-6] ./*.css | wc -l
grep -ir color=auto h[1-6] ./*.css | wc -l

# Copy file to clipboard
pbcopy < file.txt

grep -iw "is" demo_file
  // This example is the regular grep where it is searching for “is”.
  // When you search for “is”, without any option it will show out “is”, “his”, “this”

grep -B 2 "single WORD" demo_text
  Example to show the difference between WORD and word
  
  * 192.168.1.1 - single WORD

grep -A 3 -i "example" demo_text
  Example to show the difference between WORD and word
  
  * 192.168.1.1 - single WORD
  * 192.168.1.1 - seven words.

grep -C 2 "Example" demo_text
  word - word consists of a sequence of letters, digits and underscores.
  
  Example to show the difference between WORD and word
  
  * 192.168.1.1 - single WORD
  

Highlighting the search using GREP_OPTIONS

As grep prints out lines from the file by the pattern / string you had given, if you wanted it to highlight which part matches the line, then you need to follow the following way.
When you do the following export you will get the highlighting of the matched searches. In the following example, it will highlight all the this when you set the GREP_OPTIONS environment variable as shown below.
    
    $ export GREP_OPTIONS='--color=auto' GREP_COLOR='100;8'
    $ grep this demo_file
    this line is the 1st lower case line in this file.
    Two lines above this line is empty.
    And this is the last line.
  
Pipes

Pipes let you use (very simple, I insist) the output of a program as the input of another one

  ls -l | sed -e "s/[aeio]/u/g"