Summary

This is a collection of commands and facilities which occasional Unix users (eg Web site owners) use and need.

In the formal descriptions of commands, bold type means the keyword or value described is compulsory; normal type means it is optional; and slanted type means that the mnemonic must be replaced by an appropriate value. Ellipsis (…) means the preceding item is repeatable.

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Whole document

  1. Using Unix
    1.  Typing commands
    2.  The Unix file system
  2. Getting access
  3. Navigation
  4. File management
  5. Account management
Table of Contents
ToC

ToC1. Using Unix

Unix is a computer operating system. Strictly speaking, ‘Unix’ refers only to systems produced under license from the descendants of Bell Systems or Berkeley University, but there are so many derivatives both free and commercial, that it's simpler to use ‘Unix’ to mean all of them, because they all work alike and often look alike.

In this document, ‘Unix’ is therefore [ab]used to include SunOS, HP/UX, Digital Unix, GNU/Linux, and Apple Macintosh OS X.

For most work, people use a graphical user interface (the X Window System or similar). However, there are some tasks for which typed commands are faster and more powerful, particularly when you need to bulk-manage groups of files or manipulate data in formats not provided for by your windowing system. If you need to manage files and folders on a server or other remote system (elsewhere on the Internet) to which you have login access, but no windowing facilities, then typed commands are your only way.

Up to start of section1.1. Typing commands

When you are logged into a Unix system, you get a chat-like interface where you can type your instructions to the computer and it will respond with results.

The computer signals its readiness to accept a new command by displaying a dollar sign ($), sometimes preceded by your username or current directory.

When you have typed a command, you must press the ↩ key after each command, otherwise nothing will happen. This is also referred to as the Enter, Return, or Newline key.

Remember you must press the ↩ key after each command, just like a chat system. Until you do so, the computer doesn't know you have typed anything, so nothing will happen.

Unix commands consist of a command name followed by options and arguments, as shown in the examples in Table 1 below.

Table 1. Examples of Unix commands

Type Command Meaning
Command with no options or arguments top display the list of most active processes running
Another command with no options or arguments passwd change my password (it will ask for it twice)
Command with one option ls -l list all file details in ‘long’ format
Command with one option and one argument ls -l thesis.pdf list details about a specific file
Command with just one argument rm thesis.tmp remove the specified file
Command with an option (-O) with its own argument (newinfo.dat) as well as an argument for the command itself (the URI) wget -O newinfo.dat   http://www.foo.com/daily/data download data from a website straight into a named file
Command with three combined options ls -laR list all files, even hidden files, and including all files in subdirectories
Command with an option and multiple arguments cp -i thesis.* /var/backup/ copy all thesis files to a backup directory but ask me before overwriting anthing

You can only do things to files and directories that you own: if they're not yours, leave them alone (or contact the system manager if you think you ought to have access).

Up to start of section1.2. The Unix file system

Like all modern computers, Unix, GNU/Linux, Apple Mac OS X, and Microsoft Windows all use a hierarchical file system (see Figure 1 below) like an inverted family tree, with the root (starting-point) at the top. The only major difference is that Microsoft Windows has multiple roots, one for each disk (called C:, D:, E:, etc), whereas all other systems only have one root (called ‘/’).

Figure 1. A hierarchical file system displayed in a graphical directory browser

The Nautilus file-manager on Ubuntu Linux

A typical directory-and-file browser, Note the ‘family-tree’ type display of the directories and their subdirectories at the left-hand side.

At any one time, you are ‘in’ a particular directory, referred to as your current working directory. When you log in, you are put into your account's home directory. If your username is jean then your home directory would typically be /home/jean or /usr/users/j/jean or something similar depending on the type of machine and how it is set up. You can show your current working directory with the pwd command, and you can change into any directory to which you are permitted access with the cd command.

Using Figure 1 above as a graphical example, you are in /dtds/tei; that is, starting with the root of the file system (/), your location is in the dtds directory, and in the tei subdirectory of that. To get there from your home directory, you would type  cd /dtds/tei  ↩. This is an absolute reference, because it works from anywhere on the system, and always goes to the same place.

Within this directory, however, you would refer to any of the four subdirectories of the current working directory simply by name; for example  cd p4x  ↩. These are called relative references, because they relate only to the directory you are in when you use them. You could type  cd /dtds/tei/p4x   but there would be little point if you're already in the /dtds/tei directory.

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Electronic Publishing Unit • 2008-11-19 • (other)