[TCC]$ : sed basics
[TCC]$ : Many commands put something on screen like
[TCC]$ echo Today is %DATE%
Today is 2013-06-25

[TCC]$ : Sed accepts piped input and does things to it
[TCC]$ : It can print a line number before each line:
[TCC]$ echo Today is %DATE% | sed "="
1
Today is 2013-06-25

[TCC]$ : It can print something above or below a line
[TCC]$ echo Hello, world. | sed -e "1i ABOVE IT" -e "$a and BELOW it"
ABOVE IT
Hello, world.
and BELOW it

[TCC]$ : In front or after it ....
[TCC]$ echo Hello, world | sed "s/^/IN FRONT::|/; s/$/|::AFTER/"
IN FRONT::|Hello, world|::AFTER

[TCC]$ : It can delete everything but certain lines,
[TCC]$ : like here is the last line of a help file:
[TCC]$ for /? | sed "$!d"
        /L (counted loop)

[TCC]$ : It really shines at substitutions
[TCC]$ echo Today is %DATE% | sed "s,-,/,g"
Today is 2013/06/25

[TCC]$ : Or it can swap things around
[TCC]$ echo Today is %DATE% | sed -r "s/([^ ]+) ([^ ]+) ([^ ]+)/\3 \2 \1/"
2013-06-25 is Today

[TCC]$ : sed can do lots more. The End.