Comments on: Unix Tip: Commands

By: Dig Into Unix

Dig Into Unix — Wed, 10 Jun 2009 21:02:02 +0000

[...] Now, at this point, it’s important to understand a few things about the Terminal. For one, the commands that you can type are interpreted and carried out immediately, no waiting around. So, if you tell it to remove a file, it will do it right then, with no easy way of recovering it. There isn’t a recycle bin on the command line (not without a little coaxing anyway). Secondly, since Unix was developed decades ago, many of the commands seem a bit archaic. Back when most of these utilities were written, they were all abbreviated to save space and cut down on the number of keystrokes you’d need to type. Below is a list of a few essentials, and another list from Nick’s post is here. [...]

By: The Stig

The Stig — Thu, 11 Jan 2007 16:10:59 +0000

1) pwd actually stands for Print Working Directory.

2) In the above examples the use of ‘..’ to “tell” cd to move a level up isn’t quite accurate. Instead, ‘..’ is a directory itself, which links to the parent directory. All directories (or folders) have ‘..’ in them, even those at the top (/). All directories have ‘.’ in them as well, which is a directory which links to the current directory. The effect is the same but the semantics aren’t, given the writing – ‘..’ is not a special case and is not tied to the ‘cd’ command but rather part of the file system.

UNIX semantics become important as you go deeper so it’s best to learn these concepts properly from the start.

By: Thomas

Thomas — Thu, 11 Jan 2007 13:42:22 +0000

I would put aliases last on the list of things to teach people. Over the years I can’t tell you how many people got used to their aliases and after a while they couldn’t use the standard interface to save their backsides.

Instead, I would get into more “obscure” but useful commands, such as file, cut, and so forth.

By: Lordmike

Lordmike — Thu, 11 Jan 2007 06:43:54 +0000

I forgot to mention that if you use vi or vim (vim is just an improved vi editor, Vi IMproved or something like that) you edit the file by clicking a or i, a is before the cursor and i after the cursor. When you’re done with the file you hit Escape key and the type :wq! to write the file and to quit. If you don’t want any changes saved, you can do :q! to just quit.

More info on vi here http://www.eng.hawaii.edu/Tutor/vi.html

By: Lordmike

Lordmike — Thu, 11 Jan 2007 06:29:25 +0000

The mv command is also used for renaming files. Ex. mv text1.txt text1.htm will rename text1.txt to text1.htm
Another good command is cat which is used to create files and look at files, like cat text will display the contest of the file and cat > text.txt will create the file text.txt
But if you’re just going to creat a text file I recommend using vi, vim, nano, emacs or any other good shell editor. Like vim text.txt will let you creat that textfile for editing at once.
Be careful when you use cp, because you can do cp text1 text2 and text2 will be overwritten with text1 if the file already exists.

Same with rm text* can be used to delete all files where the name begins with text and rm text * will delete text file plus every other file in that directory without telling you.

Use the who command and you will see every user logged on.

Use the less command to browse inside files without being able to edit them. Can be handy when reading README files etc.
less is more is a common quote(?!) and means that the command less shows more then the command more. If I remember correct, when you use more, you won’t be able to scroll back up. This works with less.

grep is a good command to search a file for words etc, but I would rather use spotlight for this. And I never really got around to use it much in linux.
If someone wants to continue here on tutorial of grep I’ll be glad. Seems to be a great command and probably does more then I know.

By: kristof

kristof — Wed, 10 Jan 2007 23:04:22 +0000

Another comment that can be useful is the “apropos”-command. When you want to do something, and you don’t know what the command for doing the thing you want to do is, just type

apropos “whatYouWantToSearchFor”

and it will give you a list with commands that could solve your problem.

By: Nick Santilli

Nick Santilli — Wed, 10 Jan 2007 22:42:31 +0000

thanks Howard – taking care of that now.

By: Howard Melman

Howard Melman — Wed, 10 Jan 2007 22:39:58 +0000

Just some typos: The last cp example says “cd”. Also you probably want to bold the “man ls” example.