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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-5: The Old Password Prompt

3.1.2 Changing Your Password: The passwd Command

The passwd command changes your current password. If you do not have a password, it creates one.

Type passwd and press [Return]

(UNIX displays the Old password: prompt)

Enter your current password and press [Return]

(UNIX displays the New password: prompt)

Figure 3-6 New Password Prompt

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-7 Re-Enter New Password Prompt

Enter your new password

(UNIX shows the Re-enter new password: prompt)

Retype the new password

(UNIX is verifies that you did not make a mistake)

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-8 Sample of Error Messages

Password Format

Your password must comply with the following criteria:

• The new password must differ from the old one by at least three characters

• The password must be at least six characters long and must contain at least two
characters and one number

• The password must differ from your User ID

If UNIX detects anything wrong with your password, it displays an error message and shows the New password: prompt again.

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-9 Changing a Password in the Linux Environment

The wordings of the prompts are slightly different for the Linux system, but the

command and sequence of prompts are the same.

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-10 Sample of Error Messages

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

3.1.3 General Rules for Choosing Passwords

• Do not use a dictionary word (in any language)

• Do not use the name of a person, pet, location, or a character from a book

• Do not use any variation of your name and ID/account name

• Do not use known information about you, such as your phone number, birthday,
and so on

• Do not use a simple pattern or easy sequence of keyboard keys

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

3.1.4 Logging Off

The process of signing off when you have finished with the system is called
logging off or logging out

To log off, press [Ctrl-d], which means to simultaneously hold down the key
labeled Ctrl (for Control) and press the letter d

UNIX responds first by displaying logging off messages

Then UNIX shows the system’s standard welcome message and login: prompt

exit command

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-11: The Logging-In and Logging-Out Process

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-12 The Command Line Format

3.2.2 Basic Command Line Structure

Each command line consists of three fields:

• Command name

• Options

• Arguments

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-13 The date Command

3.2.3 Date and Time Display: The date Command

The date command displays the current date and time on the screen

The date and time are set by the system administrator and users cannot
change them

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

3.2.4 Information on Users: The who Command

The who command lists the login names, terminal lines, and login times of

the users who are currently logged on the system

The who command is used to check the level of activity in the system or to
find out whether a particular person is on the system

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-14 The who Command

1. The first column shows the login name of the user

2. The second column identifies the terminal being used

3. The tty number gives you some indication about the location of the terminal

4. The third and fourth columns show the date and time that each user logged in

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-15: The who Command with am i Argument

Type who am I or who am I

(UNIX displays who the system thinks you are)

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

who Options

Table 3.1 lists some of the who command options

Linux also provides some alternative and new options

Under Linux, some of these options are not available, or some of the options outputs are slightly different

1. Linux new and alternative options are listed under the Linux heading in Table 3.1

2. Linux new and alternative options are preceded by two minus signs (--)

Table 3.1 The who Command Options

Option	Linux	Operation
-q	--count	The quick who; just displays the name and number of users
-H	--heading	Displays heading above each column
-b	Displays the time and date of the last reboot
--help	Displays a usage message

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-16A The who Command with -H Option

Figure 3-16B The who Command Using Linux --heading Option

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-17A The who Command with -q Option

Figure 3-17B The who Command Using Linux --count Option

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-18 The who Command with -b Option

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-19 The who Command Using Linux --help Option

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

3.2.5: Display a Calendar: The cal Command

The cal command displays the calendar for the specified year.

If the year and the month are both specified, then the calendar for just that
month is displayed
The default argument for the cal command is the current month

Displaying the calendar for the current month (see Figure 3.20).

(Assuming current month, year is November 2005)

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-20 The cal Command with No Option

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-21 The cal Command Output

Notes:

Type the specified year in full year value. For example, type cal 2010 (not cal 10)

Use the month number (1 to 12) and not the month name

The cal command without arguments displays calendar of the current month

The cal command with year argument but without month argument displays a calendar for the specified year

Displaying the calendar for November 2010.

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-22 Learn Utility Main Menu

3.3 GETTING HELP

3.3.1 Using the learn Command

The learn command brings up a computer-aided instruction program that is arranged in a series of courses and lessons.

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-23 Help Utility Main Menu

3.3.2 Using the help Command

The help command is more popular than the learn command and is available on many UNIX systems.

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

3.3.3 Getting More Information: The UNIX Manual

You can find a detailed description of the UNIX system in a large document called the User’s Manual.

Some installation may have a printed copy of this manual

The electronic version of the manual is stored on disk and is called the
online manual

The UNIX user’s manual is tersely written and difficult to read

It is more like a reference guide than a true user’s manual

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

3.3.4 Using the Electronic Manual: The man Command

The man (manual) command shows pages from the online system documentation.

Type man followed by the name of the command

You can use man to get the details about the commands

For example type:

man cal [Return]
(UNIX responds by showing a page similar to Figure 3.24)

Note:

Nearly all UNIX installations provide the man pages, and the man command is the most popular way to obtain detailed information about command usage and options.

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-24 man Utility Display of cal

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

3.4 CORRECTING TYPING MISTAKES

The shell program interprets the command line after you press the [Return] key.

Erasing Characters
Use the [Backspace] key for erasing characters or use [Ctrl-h] once for each

character you intend to erase

Erasing an Entire Line
You can erase an entire line any time before pressing [Return]

[Ctrl-u] removes the entire command line and the cursor moves to a blank line

The character that erases the entire line is called the kill character

Terminating Program Execution
The character that terminates your running program is called the interrupt character

On most systems, [Del] or [Ctrl-c] is assigned as the interrupt character

The interrupt character stops the running program and causes the shell prompt $ to

be displayed

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Chapter 3: Getting Started

Amir Afzal
UNIX Unbounded, 5th Edition

Figure 3-25 UNIX Error Message