$ pwd
/Users/joe_user

This means that you are currently working in the "joe_user" directory, which is itself inside the "Users" directory. If you are on a Windows machine, you may notice this "path" to the working directory gets printed in a slightly different way. The above path, for example, might show up as C:\Users\joe_user. Two things should draw your attention. First, in Windows a path to a directory starts with a drive letter followed by a colon (i.e., C:), indicating on which drive the directory can be found. Second, the slashes that separate the directory names are reversed. Microsoft has always used the backslash "\", while Macs (and Unix) prefer the forward slash "/". There are no right or wrongs here -- just different systems behaving slightly differently.

Listing the Contents of a Directory (ls)

You can see what files and directories are in a directory with the ls command. It's simplest usage -- typing ls at the command prompt and hitting return will produce a list of all files and directories in the working directory, in alphabetical order. Windows shows these names together with information regarding creation dates and times, file sizes, etc... while in Mac OS-X+, one needs to type ls -l to get more than just the names of the files and directories (note, the extra "l" stands for "long form"), as can be seen in the example below:

Mac OS-X+:

$ ls -l
total 1296
-rw-r--r--@  1 oser  staff   28002 Aug 12 13:06 oxford_logo.gif
-rw-r--r--@  1 oser  staff   11747 Aug 12 13:08 math_center_banner.gif
-rw-r--r--@  1 oser  staff  158840 Aug 12 13:39 mandlebrot_set.jpg
drwxr-xr-x  50 oser  staff    1700 Jul  3 19:15 java_programs
-rw-r--r--   1 oser  staff      16 Aug 13 15:16 test.txt

Windows:

$ ls
    Directory: C:\Users\oser\Desktop\

Mode                LastWriteTime       Length Name
----                -------------       ------ ----
d----         8/13/2013   3:35 PM              java_programs
-a---         4/29/2013   8:11 AM       158840 mandlebrot.gif
-a---         4/29/2013   8:13 AM       11747  math_center_banner.gif
-a---         4/29/2013   7:17 AM       28002  oxford_logo.gif
-a---         4/29/2013   6:11 AM       16     test.txt

Note, in both cases above, the current working directory has another directory inside of it called java_programs. We know this sub-directory is a directory because of the little leading "d" at the beginning of the corresponding row.

Changing Directories (cd)

You can change your working directory with the cd command. For example, assuming that your current working directory has three directories inside of it, named "college", "home", and "work". We can make the change the working directory to "college" with cd college as the below shows:

$ pwd
/Users/joe_user
$ cd college
$ pwd
/Users/joe_user/college

If you need to change the working directory to the directory that encloses the current directory (which is called the working directory's parent directory), you can refer to that directory with two periods typed in succession (i.e., ..). So, to continue our example from above -- if we wished to change the current working directory from college back to joe_user, we might do the following:

$ pwd
/Users/joe_user/college
$ cd ..
$ pwd
/Users/joe_user

To get to an even "higher" directory, we simply use the .. symbol more than once, as shown here:

$ pwd
/Users/joe_user/college
$ cd ../../
$ pwd
/Users

You can also change directories by providing a path to the directory in question. This directory can be either absolute or relative. To see the difference between the two, suppose the directory college used in the example above had another directory in it called cs170, and our current working directory was /Users/joe_user. To change our working directory to cs170, we might do the following:

$ pwd
/Users/joe_user
$ cd /Users/joe_user/college/cs170
$ pwd
/Users/joe_user/college/cs170

The above is an example of using an absolute path to a directory. Often however, we can often be more efficient (i.e., type less) by using a relative path to the directory (or file) in question, like the below demonstrates:

$ pwd
/Users/joe_user
$ cd college/cs170
$ pwd
/Users/joe_user/college/cs170

More Commands...

---

The cat command

This command allows one to print to the screen the contents of a text file.

Example:

• To print the text found in the file my_poem.txt:

  cat my_poem.txt

---

The cp command

This command allows one to make a copy of a file or directory

Examples:

• To make a copy of the file named some_existing_file in the current directory, naming the new copy new_copy and placing it in the same directory:

  cp some_existing_file new_copy

• To make a copy of the file named some_existing_file in the current directory, naming the new copy newcopy and placing it in the parent directory:

  cp some_existing_file ../newcopy

• To make a copy of the file some_file that exists in the directory /Users/student00/project1/, giving the copy with the same name and placing it in the directory /Users/student00/project2/, presuming the current directory is /Users/student00/:

  cp /Users/student00/project1/some_file /Users/student00/project2/

  To do the same thing more briefly by using relative paths:

  cp ./project1/some_file ./project2/

• To make a copy of a directory named some_existing_directory and all of its contents -- assuming some_existing_directory resides in the current directory -- and naming the new directory new_directory and placing it also in the current directory:

  cp -r some_existing_directory new_directory

  The cp command doesn't copy all of the contents of a directory by default. We tell the cp command that we want it to copy all of the contents by including the "-r" flag.

---

The mv command

This command allows one to rename and/or relocate a file.

Examples:

• To rename the file junk found in the current directory to the file precious:

  mv junk precious

• To move the file precious from the current directory to a directory treasure also in the current directory:

  mv precious treasure

• To move the file jewel to a directory casket also in the current directory and rename it to amethyst:

  mv jewel casket/amethyst

• To move a directory bag_of_diamonds to a directory safety_deposit in the parent directory, while renaming it rainy_day_fund:

   mv bag_of_diamonds ../safety_deposit/rainy_day_fund

---

The rm command

This command allows one to remove an existing file.

Example:

• To remove the file named junk.txt from the current directory:

  rm junk.txt

---

The mkdir command

This command allows one to make a new directory of a given name.

Examples:

• To make a directory named alice in the current directory:

  mkdir alice

• To make a directory named bob in the parent directory:

  mkdir ../bob

---

The rmdir command

This command allows one to remove an existing directory.

Example:

• To remove the directory empty_folder from the current directory:

  rmdir empty_folder

---

The man command

This command allows you to learn about any other command. The metaphor here would be looking up the command in question in the "manual". Invoking man will bring up text detailing the command in question, citing what it does, how it and it's arguments should be called, what happens when optional flags are provided, and so on...

Example:

• To learn more about the java compiler command, javac:

  man javac

---

The nano editor

nano is a simple text editing program that will run in a terminal/console window. Note, in such a program, one obviously doesn't have the benefit of a mouse. Thus, moving the cursor around must be done with the arrow keys and other keyboard shortcuts. Copying and pasting, searching for specified text, indenting, and other operations are all handled in this way -- through the use of keyboard shortcuts.

Note: The nano editor does not come as a standard part of the windows operating system, so to use it in this environment you must install it first. (See nano for windows)

Example

• To create a new text file called myTextFile and immediately start editing it:

  nano myTextFile

  Once you are in editing mode, type "Ctrl-g" to bring up the help document that details all of the keyboard shortcuts you can perform within the editor itself.

---

The vim editor

vim is a much more powerful text editing program that also runs in a terminal/console window. The learning curve, however, is substantially steeper. If you want to learn how to use it, this interactive tutorial is a nice gentle way to start...

Note: The vim editor does not come as a standard part of the windows operating system, so to use it in this environment you must install it first. (See vim for windows)

Example

• To create a new text file called myTextFile and immediately start editing it:

  vim myTextFile

  Your are strongly encouraged to read through the aforementioned tutorial (or some other tutorial on vim) before executing something similar to the above -- if for no other reason than learning how to exit the editor (it's not obvious)!