It's $ for normal commands, and # for system-administration. You mustn't actually type these when you enter a command.
Unix commands
The pipe symbol is a vertical bar (|), not a forward slash.
It depends on which networking protocol you are asking about. For TCP/IP, some of the common commands are: ping netstat ifconfig route traceroute
Commands you use in a Unix based computer OS to achieve certain things. Similar to MS/DOS commands in Windows. Mostly used in computers running the Linux OS. unix command
The lp and lpr commands are the traditional commands used to print jobs on UNIX.
It would take a very long time to learn all of the Unix commands, and frankly, that isn't necessary. Most Unix users have a subset of commands they use all the time, and that is how they learn them.
Because Linux evolved from UNIX, but Windows evolved from DOS.
Man (or manual) pages
Unix files do not rely on extensions, therefore there is no command to find them.
There is none. For starters, you have it backwards, DOS actually copied most of its commands from Unix (The rest came from CP/M.), which Linux is inspired by. Commands like "cd" and "dir" were Unix commands long before DOS even existed.
Most of MS-DOS' commands were based on those of Unix and CP/M. 'cd', 'dir', 'clear', and 'echo' are usually found in both. MS-DOS added it's own commands, however, and made some different from those of existing versions of Unix, and no one saw any reason to change the names of existing ones in Unix.
William Holliker has written: 'UNIX Shell commands quick reference' -- subject(s): UNIX (Computer file), UNIX Shells