Unix Navigation Commands

Here is an overview of commands [ Unix ] for navigating around the filesystem.

You use commands from the terminal app.

Macintosh-HD -> Applications -> Utilities -> Terminal

Why the terminal is so cryptic? Here is a picture of an early terminal. It was a piece of hardware not an app.

The terminal is designed for little fuss and maximum power. Be careful. Please have a full backup of your system before using terminal commands. The only mildly dangerous command that I mention is the mv command. Avoid it to reduce your risk.

Check all commands twice to avoid mistyping.

In all cases, you type the command after the prompt. Generally, prompts end with a $. You press the return key to run the command. You must use the larger delete key to backup and delete the prior character. The use of the mouse inside the terminal window acts a little different. You may copy from anywhere as before, but paste will always paste to where the terminal cursor is. The terminal existed before the mouse was invented!

"mac $" is my terminal prompt. Your prompt will be different.

What is my short user name?

Type the whoami command. Then press the return key. The terminal types out the answer. In my case, my single user name is "mac". Yours will be different.

mac $ whoami

mac

mac $

How to list all of your disk names.

The ls command is for list.

mac $ ls /Volumes/

Audio CD Macintosh-HD Spotless Tiger-ext mac $

Let's say your flash drive is named Spotless

cd -- Change directory

# cd is change directory

# for historical reasons, folders are called directories when using terminal commands.

# so, you end up with the command cd.

mac $ cd /Volumes/Spotless

pwd -- print working directory

# pwd is Print Working Directory. A directory is the Unix name for a folder. You always have a default directory.

# You use the pwd command to see what it is.

mac $ pwd

/Volumes/Spotless

mac $

ls -- list files

# The ls command is for list. The letter l is a lower case L.

# l is long

# F is type of file where / is directory. For directories, the slash is pasted to the end of the name.

mac $ ls -lF 
total 134704
-rw-r--r--     1 mac  staff     64560 Mar  3  2009 A-picture-of-Youpi-key.png 
drwxr-xr-x    83 mac  staff      2822 Nov  7 14:52 Applescript files/ 
drwxrwxrwx    12 mac  staff       408 Dec 13  2008 Christmas Cards/ 
drwxr-xr-x     9 mac  staff       306 Dec 21 17:39 Christmas Cards 2009/ 
... trimmed ...

What does all this mean?

# l is long
# F is print what kind of file is listed.
# a is all to show hidden files & directories.
mac $ ls -lFa 
total 134736 
drwxr-xr-x    41 mac  staff     1496 Dec 22 17:11 . 
drwxrwxrwt     8 root admin      272 Dec 24 13:55 .. 
-rwxrwxrwx     1 mac  staff    15364 Dec 23 12:52 .DS_Store* 
drwx------     4 mac  staff      136 Jan 22  2009 .Spotlight-V100 
drwxrwxrwt     5 mac  staff      170 Sep 14 16:36 .TemporaryItems 
d-wx-wx-wx     4 mac  staff      136 Dec 31  1969 .Trashes 
-rw-r--r--     1 mac  staff    64560 Mar  3  2009 A-picture-of-Youpi-key.png 
drwxr-xr-x    83 mac  staff     2822 Nov  7 14:52 Applescript files 
drwxrwxrwx    12 mac  staff      408 Dec 13  2008 Christmas Cards 
drwxr-xr-x     9 mac  staff      306 Dec 21 17:39 Christmas Cards 2009
 ... trimmed ...

d = directory 

Next is a triplet of permissions for the owner, group and other.
r = read 
w = write 
x = executeable program
- = you do not have this permission 

drwxrwxrwx 
↑↑  ↑  ↑   
||  |  other -- all other users not in first two types 
||  |   
||  group
|| 
|owner 
|  
What type of entry is this? d = directory, - = file, etc.
    
    Every Unix resource: files, folders, etc has an owner, group, other permission. 
    • Unix resource has one owner.
    • Unix resource has one group.  A group contains a list of users.
    
    To gain access to a file, you can be the owner, in the group, or not the owner and not in the group hence you end up as other. The owner, group, or other  has read, write, or execute permissions.

mv -- Move

# mv is move or rename

# The mv command can be dangerous. It lets you destroy an existing file.

# Always use the -i option to avoid issues. Be sure to take your time.

# -i for interactive which prompts you before overwriting an existing file

mv -i the-name the-new-name

# You can just rename the file back to what it was with mv command.

mv -i old-name new-name

Here is what these commands mean:

cd is change directory

pwd is a print working directory

ls is list

sudo is Super user do

mv is move or rename

man -- manual

For cryptic comments, you can always uses the manual command which is man. For example:

man mv

Type the letter q to quit the man command.

You sometimes see the tilde ~ in Unix commands. It means your home directory.

mac $ pwd /Users/mac/Downloads mac $ cd ~ /Users/mac mac $ pwd /Users/mac mac $

In case you have spaces in your filenames or directories, you need to escape them. Use quotes around the name or a backslash before each space.

mac $ ls -l ~/"see it"

-rw-r--r-- 1 mac staff 3171 Oct 26 23:38 /Users/mac/see it

mac $ cd /Users/mac/Desktop/ttt\ html\ copy/

command line features

Do you know about tabbing? Type in a few letters of a file or directory name then press the tab key. The computer will type out the rest of the name if it is unique.

Press the up arrow key to see the previous command(s).

To edit a command, use the left arrow key to more left and the right arrow key to move right. Use the delete key to delete the key to the left. Type a letter to insert.

history -- print previous commands

history to see many previous commands.

mac $ history

1 pwd

2 man ls

3 history

You may copy then paste from this list.

Robert

PS. fyi: The commands also work in Single User Mode.

Start up your Mac in single-user mode or verbose mode - Apple Support