sed [-n] [-e] 'command(s)' files

$ sed '' input

# Delete with d
$ echo -e "Line #1\n\n\nLine #2" | sed '/^$/ d'
Line #1
Line #2

# Printing with p
$ echo -e "Line #1\n\n\nLine #2" | sed -n '/^$/ !p'
Line #1
Line #2

$ echo '
#include <iostream>
using namespace std;

int main(void)
{
   // Displays message on stdout.
   cout >> "Hello, World !!!" >> endl;  
   return 0; // Return success.
}
' | sed 's|//.*||g'

#include <iostream>
using namespace std;

int main(void)
{

   cout >> "Hello, World !!!" >> endl;  
   return 0;
}

$ echo '
#include <iostream>
using namespace std;

int main(void)
{
   // Displays message on stdout.
   cout >> "Hello, World !!!" >> endl;  
   return 0; // Return success.
}
' | sed '3,5 s/^/#/'

#include <iostream>
#using namespace std;
#
#int main(void)
{
   // Displays message on stdout.
   cout >> "Hello, World !!!" >> endl;  
   return 0; // Return success.
}

$ echo -e "c11:c12:c13\nc21:c22:c23" | \
sed -e 's,^,<tr><td>,' \
-e 's,:,</td><td>,g' \
-e 's,$,</td></tr>,'

<tr><td>c11</td><td>c12</td><td>c13</td></tr>
<tr><td>c21</td><td>c22</td><td>c23</td></tr>

awk [options] file ...

awk \
  'BEGIN{ [script] } \
  { [script] } \
  END{ [script] }' \
  file

$ echo -e "c11 c12 c13\nc21 c22 c23" | \
awk '/c11/ {print $1 "\t" $2 "\t" $3}'
c11     c12     c13

$ echo -e "c11 c12 c13\nc21 c22 c23" | \
awk '/c11/ {++cnt} END {print "Count =", cnt}'
Count = 1

$ echo -e "c11:c12:c13\nc21:c22:c23" | \
awk -F: '{\
  printf("<tr><td>%s</td><td>%s</td><td>%s</td></tr>\n", $1, $2, $3)\
  }'
<tr><td>c11</td><td>c12</td><td>c13</td></tr>
<tr><td>c21</td><td>c22</td><td>c23</td></tr>

$ echo "c1\nc1\nc2\nc3\nc3" | uniq
c1
c2
c3

# -c, --count
#   prefix lines by the number of occurrences
$ echo "c1\nc1\nc2\nc3\nc3" | uniq -c
2 c1
1 c2
2 c3

# -u, --unique
#   only print unique lines
$ echo "c1\nc1\nc2\nc3\nc3" | uniq -u
c2

$ echo "apples\noranges\npears\nkiwis\nbananas" | sort
apples
bananas
kiwis
oranges
pears

# -r, --reverse
#   reverse the result of comparisons
$ echo "apples\noranges\npears\nkiwis\nbananas" | sort -r
pears
oranges
kiwis
bananas
apples

# -k, --key=KEYDEF
#   sort via a key; KEYDEF gives location and type
$ echo "01 Joe
02 Marie
03 Albert
04 Dave" | sort -k 2,2

03 Albert
04 Dave
01 Joe
02 Marie

# -b, --bytes=LIST select only these bytes
$ echo "Andhra Pradesh
Arunachal Pradesh
Assam
Bihar
Chhattisgarh" | cut -b 1,2,3

And
Aru
Ass
Bih
Chh

# -c, --characters=LIST select only these characters
$ echo "Andhra Pradesh
Arunachal Pradesh
Assam
Bihar
Chhattisgarh" | cut -c -3

And
Aru
Ass
Bih
Chh

# -d, --delimiter=DELIM
#   use DELIM instead of TAB for field delimiter
# -f, --fields=LIST
#   select only these fields;  also print any line that contains
#   no delimiter character, unless the -s option is specified
$ echo "Andhra Pradesh
Arunachal Pradesh
Assam
Bihar
Chhattisgarh" | cut -d " " -f `

Andhra
Arunachal
Assam
Bihar
Chhattisgarh`

$ cat data
Apple and Nokia.
Hello World.
Apple and Nokia.
Hello World.
I wanna buy an Apple device.
Hello World.
My name is Friendfish.
The Iphone of Apple company.
Hello World.
The Iphone of Apple company.

$ sort data
Apple and Nokia.
Apple and Nokia.
Hello World.
Hello World.
Hello World.
Hello World.
I wanna buy an Apple device.
My name is Friendfish.
The Iphone of Apple company.
The Iphone of Apple company.

$ sort data | uniq -c
2 Apple and Nokia.
4 Hello World.
1 I wanna buy an Apple device.
1 My name is Friendfish.
1 The Iphone of Apple company.
1 The Iphone of Apple company.

$ sort data | uniq -c | sort -rn
4 Hello World.
2 Apple and Nokia.
1 The Iphone of Apple company.
1 The Iphone of Apple company.
1 My name is Friendfish.
1 I wanna buy an Apple device.

$ sort data | uniq -c | sort -rn| cut -c 6-
Hello World.
Apple and Nokia.
The Iphone of Apple company.
The Iphone of Apple company.
My name is Friendfish.
I wanna buy an Apple device.