Unix Summary
A Survival Guide

Module Q02cd

Contents

Audience and Objectives

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Quick Reference

NOTE: Most concepts are explained in more detail below the quick reference

Unix Conventions:

 

The Unix Prompt

To let you know it is ready to accept your commands, Unix displays a"prompt" on the screen. This prompt can be set to be just about anything. It may be:

Getting and Interpreting File and Directory Listings

Listing a Directory:

Simple:
ls
File:
ls filename.typ
All files with the same ending:
ls *xy123
All files with the same beginning:
ls name*
Files the same except for one letter:
ls nam?.ending
All files in a specific directory
ls /user/jones/public_html/*
Detailed:
ls -l
List hidden files too:
ls -a
Send listing to printer:
ls > lpr
Putting features together:
ls -al /user/jones/public_html/*.gif > lpr

Interpreting a Simple Directory Listing: 

orchard:krieg% lsMail                    mailing-lists           peg_acpt.uuPEG_ACPT.TXT            modflow.doc             pegasus.txt TEST                    msen_mail               public_htmldecomout.htm            na13he_1.doc            science.htm?desrvcri.doc            netfind.txt             searchou.htmlynx_bookmarks.html     nw1                     sigmachist.txt             pasguide.txt            soapmail                    peg_acpt.txt            williams.doc

The Details...

Files are listed by name, in columns. They are in alphabetical order by column. Notice that since Unix is case-sensitive, files beginning with capital letters are sorted to the top of the list. Notice also that directories are not distinguished from files.

Interpreting a Full Listing

(This is an excerpt from a terminal session. Bold shows what the user typed; Normal shows what the system prints; comments and explanations are in italics.) 

orchard:krieg% ls -l total 286                       (total number of disk "blocks" used)drwx------  2 krieg         512 Jun  7  1995 Mail-rw-rw----  1 krieg        2050 Feb  1 20:47 PEG_ACPT.TXT-rw-rw----  1 krieg          49 Feb  5 13:24 TEST-rw-r--r--  1 krieg         537 Feb 13 14:27 decomout.htm-rw-r-----  1 krieg       16384 Feb  9 13:26 desrvcri.doc-rw-r-----  1 krieg        1075 Nov 12 16:37 lynx_bookmarks.html-rw-r-----  1 krieg        9784 Mar 12 14:33 machist.txtdrwx------  2 krieg        1024 Mar 19 14:10 maildrwxr-x--x  2 krieg         512 Sep 24 07:10 mailing-lists-rw-r--r--  1 krieg       66048 Jan 30 18:09 modflow.docdrwx------  2 krieg         512 Apr 22  1995 msen_mail-rw-r--r--  1 krieg       64000 Feb 14 14:10 na13he_1.doc-rw-r-----  1 krieg       71779 Feb  9 11:50 netfind.txt-rw-r-----  1 krieg         551 Feb 12 16:47 nw1-rw-r-----  1 krieg         723 Jan 30 18:01 pasguide.txt-rw-r-----  1 krieg           0 Feb  1 20:47 peg_acpt.txt-rw-r-----  1 krieg        4118 Feb  1 20:43 peg_acpt.uu-rw-r-----  1 krieg         599 Feb  5 13:18 pegasus.txtdrwxr-x--x  2 krieg        3584 Mar 16 14:44 public_html-rw-rw-rw-  1 krieg       16663 Dec  6 22:05 science.htm?-rw-r--r--  1 krieg         544 Feb 13 14:27 searchou.htm-rwx------  1 krieg         415 Jul 25  1995 sig-rw-r-----  1 krieg       10460 Feb 21 16:41 soap-rw-r-----  1 krieg        8192 Feb 10 16:33 williams.doc-Mode---Links-Owner-------Size-----Date------File Name----

The MODE printed under the -l option contains 10 characters interpreted as follows. If the first character is:

d
entry is a directory;
-
entry is a plain file.

The next 9 characters are interpreted as three sets of three bits each.

Within each set the three characters indicate permission respectively to read, to write, or to execute the file as a program. For a directory, "execute" permission is interpreted to mean permission to search the directory. The permissions are indicated as follows:

r
the file is readable;
w
the file is writeable;
x
the file is executable;
-
the indicated permission is not granted.

The SIZE is listed in bytes. (A byte is enough space to hold one character.)

The DATE is month, day, and time the file was modified(using 24-hour clock). If the file was modified more than 6 months ago, the ls command will give the year instead of the time.

The FILE NAME is listed in alphabetical order, though other list orders can be generated using command modifiers.

For more information about the ls command, when you are using a Unix machine, type
man ls
to see the manual for this command.

Using "Metacharacters:" File Name Substitution

Unix commands that deal with files allow you to specify files by name, or to approximate names by using "metacharacters"("wldcards") that match several file names.

File name substitution can be used with just about any commands that deal with files: ls, cat, more, chmod, rm, and many others.

Matching any group of characters:
* (star, or asterisk) matches any group of letters in the file name
Matching any single characters:
? (question mark) matches any single letter in the file name.
Matching specific characters:
[ ] brackets can enclose groups of letters or ranges of letters to be matched.

Examples:

more *
Show contents of all files in the current directory
ls *.html
List all files ending with .html
ls prog1*
List all files beginning with prog1 regardless of what they end with
ls *.*
List all files containing the period (dot) character anywhere in them
ls chapt?
List all files beginning with chapt and containing exactly one more letter. This will match chapt0 chapt1 chaptx
but will not match chapt chapt10 chapt.txt
rm chapt[0123]
Remove (delete) files matching chapt0 chapt1 chapt2 chapt3
and no others
rm chapt[0-3]
Same as above - this is just an abbreviation
ls [a-z]*
List all files whose first character is a lower-case alphabetic letter.
ls *[a-df-z]
List all files ending with any lower-case alphabetic character excepte

Changing Default Directory

Like most operating systems, Unix has a hierarchical directory structure. (See Background...Directory Structure below.) You can change the default (working) directory to save the effort of typing the full "path name." (The path is the list of all directories between the root and the target directory.)

Change directory:
cd directory_name
Print working directory name:
pwd

Example:

(This is an excerpt from a terminal session. Bold shows what the user typed; Normal shows what the system prints; comments and explanations are in italics.) 

orchard:krieg% pwd                       (Where are we?)/usr/local/users/krieg                   (My home directory!)orchard:krieg% cd /                      (Change to the root directory)/                   (This system prints the working directory when you change)orchard:krieg% pwd                       (I print working directory anyway)/orchard:krieg% ls                        (Check the file listing...)bin             dev        lost+found   sys boot            etc        mnt          tmpbuild           export     pcfs         usrcdrom           kadb       root         varconduit         lib        sbin         vmunixorchard:krieg% cd etc                    (Change to another directory)/etcorchard:krieg% ls??              inetd.conf              rc.nfs...                                      (Listing too long to show all)hosts.equiv             rc.ip           xinetd.confifconfig                rc.local        xtaborchard:krieg% cd ..                     (Change to next directory up)/                                        (It's the root)orchard:krieg% cd usr                    (Now we'll work our way back home)/usr orchard:krieg% cd local/usr/localorchard:krieg% ls orchard:krieg% cd users/usr/local/users orchard:krieg% cd krieg/usr/local/users/kriegorchard:krieg% ls                        (I list my home directory)Mail                    msen_mail               siglynx_bookmarks.html     nw1                     soapmail                    pasguide.txtmailing-lists           public_html orchard:krieg% cd public_html            (Now I change to a subdirectory)/usr/local/users/krieg/public_html orchard:krieg%

Handling Files: Copying, Moving, Deleting, and Renaming

Copy from default to archive directory
cp file.txt archive
(file.txt now exists in two directories)
Move from default to archive directory
mv file.txt archive
(file.txt now exists in only in the archive directory)
Copy from archive to default directory
cp archive/file.txt
Copy all files in a directory to default
copy archive/*
Remove (Delete) one file
rm file.txt
Remove all files in a directory
rm archive/*
Delete all files in the current directory whose name begins with the letter q
rm q*
Rename a file.abc to be file.xyz
mv file.abc file.xyz
Rename all files ending .abc
mv *.abc *.xyz

Background Concepts

Unix Disk Concepts

Computers using Unix have access to files stored on one or more disk. Here are some facts about how Unix handles its disks:

Directories

A directory is a part of a disk whose files can be handled as a separate group. What the Macintosh calls "folders"are the "directories" of Unix. This concept is useful because disks can hold such large numbers of files that, without some way of organizing them into groups, it would be nearly impossible to deal with them rationally. Also, directories provide a space where files can be kept private from other users.

Directory background

Unix Directory Rules

Default Directory

Since we have to type all Unix commands, any way of shortening commands is helpful. One such technique is by defining a default directory - a (sub)directory which Unix assumes you want to use. That way, you don't have to type it out every time you refer to its files. You can think of Unix as always "looking at"the default directory.

The default directory is changed by giving the cd command.You can cd to any directory in the current directory, or if you list the entire path, you can cd to any directory on the system.

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Unix File Name Rules

Unix file names are restricted by several rules - mainly constraining their length and the characters they can have in them. Here are the basics:

Parts

Overall:
Unix file names can be as long as you like (just about).
Name:
Every file must have a name. Names are useful for explaining what the contents are about. Examples:
a
taxes
budget94
96income
slurp

Characters

Other Helpful Unix References

Audience:

This is for people who have at least learned how to turn on a computer, and need to know how to do just enough with the Unix operating system to do basic work. (This is relevant to most versions of Unix).

Objectives:

By consulting this reference guide, you will be able to...

About this document...

Module Q02cu: Unix Summary: A Survival Guide

Author:
Laurence J. Krieg
Institution:
Department of Computer Information Systems, Washtenaw Community College
History:
Original version: 19 March 1996; Latest update Friday, 16-Apr-2004 19:54:36 EDT
Copyright:
Copyright © 1996, 2004 Laurence J. Krieg, Washtenaw Community College
Instructors: You may point to this file in your Web-based materials.
Students: you may make a copy for your personal use.
All other uses: contact the author, Laurence J. Krieg for permission.