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Complete Idiot's Guide to Linux
(Publisher: Macmillan Computer Publishing)
Author(s): Manuel Ricart
ISBN: 078971826x
Publication Date: 12/22/98

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Chapter 17
Command Toolbox: Useful Shell Commands and Shortcuts

In This Chapter

  User Utilities
  Finding Files
  Text and File Utilities
  Splitting Files into Smaller Files: split
  Accessing a Computer Through the Network: telnet
  Working on the Console: setfont
  UNIX Printing Primer
  UNIX Text Processing

This chapter introduces a number of basic tools and command line programs that you can use while working on the shell. There are many more tools available, but these are some of the more basic ones. You have already learned a few in each category. Although this chapter is not comprehensive, it will give you an idea of what you will find. Many more tools are available—so many, in fact, that it could be the topic for an entire book.

User Utilities

Every once in a while during the course of your work, you will want to change your password, change your shell, find files, search files, and so on. Here are some commands to help you.

Changing Your Password: passwd

Use the passwd command to change your password. Because the command is interactive, it will ask you for your current password (to ensure that some other user doesn’t change your password while you are away from your computer) and then for a new password. After successful confirmation of your password, it is accepted by the system. Note that passwords are never echoed to the screen to avoid being spied by nearby eyes, as in the following code:

      [alberto@digital alberto]$ passwd
     Changing password for alberto
     (current) UNIX password: ******** 
     Enter new UNIX password: ********
     Retype new UNIX password: ********
     passwd: all authentication tokens updated successfully

The superuser (root) can use the same passwd command to change any password in the system. When the superuser provides a username as an option to the command, he or she can change the password for any user in the system. The superuser does not need to authenticate the user’s password. Changing a user’s password as the superuser would look like this:

     [root@digital /root]# passwd alberto
     Enter new UNIX password: ********
     Retype new UNIX password: ********
     passwd: all authentication tokens updated successfully

Changing Your Shell: chsh

If you don’t like your shell, you can use the chsh command to change it. Only shells listed in /etc/shells are acceptable for use. It can be used interactively, like this:

     alberto@digital alberto]$ more /etc/shells
     /bin/bash
     /bin/sh
     /bin/ksh
     /bin/csh
     /bin/tcsh
     [alberto@digital alberto]$ chsh
     Changing shell for alberto.
     Password: ********
     New shell [/bin/tcsh]: /bin/bash
     Shell changed.

If the shell you like is not listed, add an entry to the /etc/shells file, and then you’ll be able to set it.

Changing Personal Information: chfn

The chfn (change finger name) command changes additional information about yourself, such as your full name, office address, and office and home phone numbers. This information is accessible using the finger command (which is typically disabled in most systems because it poses certain security risks). It is used by some programs to determine your full name and other information. The chfn command, like the passwd command, is interactive:

     [alberto@digital alberto]$ chfn
     Changing finger information for alberto.
     Password: **********
     Name [Caldera OpenLinux User]: Alberto Ricart
     Office []: Rm. 3210 Left Wing
     Office Phone []: 800 555 1212 ext 800
     Home Phone []: not listed

     Finger information changed.

Who’s on the System: who and w

The who and w commands can be used to see who is logged into the system. The w tells you who is logged on and what they are doing:

      [alberto@digital /etc]$ w
      17:17:07 up  5:42,  2 users,  load average: 0.05, 0.13, 0.09
     USER     TTY      FROM              LOGIN@  IDLE   JCPU   PCPU  WHAT
     alberto  tty1                     11:51am  5:25m 33.95s  0.13s  xinit
      /etc/X11/
     alberto  ttyp0    192.168.0.10     5:07pm  1.00s  0.50s  0.08s  w

The who command simply tells you who is logged into the system:

     [alberto@digital /etc]$ who
     alberto  tty1     Sep 20 11:51
     alberto  ttyp0    Sep 20 17:07 (192.168.0.10)

Both these commands point out who is logged in through a remote terminal. The FROM column in the w command (the first example in the previous section) lists the IP address of remote users. The who command also displays the address of remote users between parentheses.


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