Shell scripting

What is the difference between $* and $@?

Unquoted, there is no difference -- they're expanded to all the arguments and they're split accordingly.

The difference comes when quoting. "$@" expands to properly quoted arguments and "$*" makes all arguments into a single argument.

What is the significance of $#?

The number of arguments supplied to a script.

sed stands for stream editor is a stream oriented editor.

It receives text input, whether from stdin or from a file, performs certain operations on specified lines of the input, one line at a time, then outputs the result to stdout or to a file.

'2,5!d'	This will deleted everything except starting from 2nd till 5th line.
'1~3d'	This deletes the first line, steps over the next three lines, and then deletes the fourth line. Sed continues applying this pattern until the end of the file.

Awk	Pattern scanning and processing language
Cmp	Compare the contents of two files
Comm.	Compare sorted data
Cut	Cut out selected fields of each line of a file
Diff	Differential file comparator
Expand	Expand tabs to spaces
Join	Join files on some common field
Perl	Data manipulation language
Sed	Stream text editor
Sort	Sort file data
Split	Split file into smaller files
Tr	Translate characters
Uniq	Report repeated lines in a file
Wc	Count words, lines, and characters