Linux System Programs

ls

List the files/directories in the "current working directory".
ls has several "switches" which control how it works.

man command

This looks up command in the online manual. This is called "looking up the man page for command". You can do a man man to read up on it. You can also do things like man ls to find out how to use ls and to see what its switches do.

man number command

This looks up command in section number of the online manual. You can use this to look up the system call read() rather than the command read. The manual is typically divided into at least 9 sections, but you probably only need to know about sections 1 through 3 and possibly 7:

• 1. User commands: things like ls, applications, etc.
• 2 System calls: programmers call these to use the machine
• 3. Library functions: higher level things called by programmers
• 7. Conventions and Miscellany: standards, conventions, protocols, file systems layout, etc.

rm file

Delete the file named. This does not move the file to a "garbage can", it gets rid of it permanently, so be careful!

rm -r directory

Recursively delete the directory and everything in it.

mkdir directory

Make a new directory in the current directory.

rmdir directory

Remove the directory from the current directory. To remove a directory, with this command you must first empty it.