Command Forms

When you log into a unix account, the primary interface is a prompt which is waiting for you to type a command. Most UNIX commands are given in the form of a command name, followed by a list of options (not required), followed by a list of arguments. The options list is preceded by a minus sign (-) and consists of one or more characters, each of which represents a different option. The arguments are typically filenames or directories. In some cases an option itself may require an argument, in which case the option is separated from the other options by spaces and another minus sign. For example, the command line

ls -al subdirectory

Files and Directories

Files on the UNIX system are grouped into directories, same as folders in a Windows environment. A directory is a collection of files and other (sub)directories. Note that files and directories must NOT have spaces in their names in a unix environment!

The "highest" directory on a unix machine is called the "root directory", and is represented by a single slash (`/'). The root directory corresponds roughly to the Desktop on a Windows PC. The list of directories starting at root which lead to a specific file location is called the "directory path" or simply the "path" of the file. When typing a path, each directory is separated from the next by a (forward) slash. [This differs from a Windows machine which uses backslashes.]

Each user account on a unix server machine is associated with a directory called its "home directory" into which the user is automatically placed upon logging in. For example, account login jhoulah1 has the home directory /users/eng/cs/6/.jhoulah1 which means that the files and subdirectories associated with that account are located in the '.jhoulah1' directory (directory corresponding to the login), which is located in the '6' directory, which is located in the cs directory, which is located in the 'eng' directory (directory for the engineering school), which is located in the 'users' directory (directory of all users), which is located in the root directory (/). Thus, if jhoulah1 has a file called cal06, the full path name of that file is "/users/eng/cs/6/.jhoulah1/cal06".

The cd (change directory) command is used to move from one directory to another. For example, if you want to go forward into a sub-directory named personal, you would type "cd personal". This corresponds to double clicking on a folder on a Windows machine. If you want to go backwards into the directory containing the one where you are, you have to use two dots to refer to this "parent directory", as in "cd ..". The directory in which a user is working is called the "current directory" and the pwd (print working directory) command can be used to get the full path of the current directory. When referring to a file in the current directory, it is not necessary to specify the full path name. In order to access a file in a subdirectory of the current directory, one can either change to that directory or use a partial path name that would look like subdirectory/filename.

Special keys

Control key functions

Keys that may not work as you expect

Often the delete (DEL) and arrow keys do not work the way you want or expect them to in a UNIX environment. If you try them and get garbage, or nothing seems to be happening, then hit ^u to undo that command line and start over with a new prompt. [Within particular programs (such as pico), the arrow keys are effective.]

Redirecting input and ouput

Unless otherwise specified, the default input and output devices are the keyboard and the screen. However, a few special characters can be used in conjunction with many commands to redirect standard input and output. They are the greater than symbol (>), the less than symbol (<) and the pipe (|).