Basic Linux Commands

1. cat command

cat is a simple little program that displays the contents of a text file when you give the file name as an argument to it:
$ cat view_this

2. less command

less is a program that lets you view text files, like cat does, but if the files are so long that they don't fit on your screen, less automatically paginates the file. You use less by giving the file name as an argument to it:
$ less view_this

3. < Copying >

To copy files, you use the cp command. The following will copy file to file2. Note that if file2 doesn't exist, it'll be created, but if it exists, it'll be overwritten:
$ cp file file2

There aren't any undo commands in the Linux CLI, so accidentally overwriting an important file would probably make you pull your head off. The risk of doing so is smaller if you use the -i option ("interactive") with cp. The following does the same as the above, but if file2 exists, you'll be prompted before overwriting:

$ cp -i file file2
cp: overwrite `file2'? n
$

So it's a good idea to use the -i option whenever you're dealing with important files you don't want to lose!

If you want to copy file into directory dir1:
$ cp file dir1

The following would do the same as the above, copy file into dir1, but under a different name:
$ cp file dir1/file2

You can also copy multiple files into one directory with a single command:
$ cp file1 file2 file3 dir1

Note that if the last argument isn't a directory name, you'll get an error message complaining about it.

4. < Moving and renaming >

The mv command can be used for moving or renaming files. To rename a file, you can use it like this:
$ mv file file2

If file2 doesn't exist, it'll be created, but if it exists, it'll be overwritten. If you want to be prompted before overwriting files, you can use the -i option the same way as with cp:

$ mv -i file file2
mv: overwrite `file2'? y
$

To move the file into another directory:
$ mv file dir1

If you want to rename the file to file2 and move it into another directory, you probably already figured out the command:
$ mv file dir1/file2

5. < Removing files >

The rm command is used for removing files and directories. To remove a file:
$ rm file

If you use the -i option, you'll be prompted before removing the file:
$ rm -i file

You can also delete more files at once:
rm file1 file2

Be careful with the rm command! As I already told you, Linux doesn't have any undo commands, and it doesn't put files into Trash where you can save them later. Once you've deleted a file, it's bye-bye!