### Sed - Stream Editor ###

1. Faciliates automated text editing
 2. Supports RegExes (POSIX)
 3. Like Awk, supports scripting using '-F' option
 4. Supports input via: STDIN, pipe, file
Usage:
 1. sed [options] 'instruction[s]' file[s]
 2. sed -n '1p' grep1.txt - prints the first line of the file
 3. sed -n '1,5p' grep1.txt - prints the first 5 lines of the file
 4. sed -n '$p' grep1.txt - prints the last line of the file
 5. sed -n '1,3!p' grep1.txt - prints ALL but lines 1-3
 6. sed -n '/linux/p' grep1.txt - prints lines with 'linux'
 7. sed -e '/^$/d' grep1.txt - deletes blank lines from the document
 8. sed -e '/^$/d' grep1.txt > sed1.txt - deletes blank lines from the document 'grep1.txt' and creates 'sed1.txt'
 9. sed -ne 's/search/replace/p' sed1.txt
10. sed -ne 's/linux/unix/p' sed1.txt
11. sed -i.bak -e 's/3/4' sed1.txt - this backs up the original file and creates a new 'sed1.txt' with the modifications indicated in the command
Note: Generally, to create new files, use output redirection, instead of allowing sed to write to STDOUT
Note: Sed applies each instruction to each line