Managing Terminals

Question 1

Bash shell, and terminal it runs on, are ______ ________ used by experianced Linux users.

Answer 1

primary tools.

Question 2

When terminals display info, they usually display…?

Answer 2

one byte at a time.

Question 3

When computers are handling human readable text, the characters are usually…?

Answer 3

Encoded as an integer byte value using the ASCII format. (One byte can encode up to 256 different values, only a small number of these (about 100) are used for text characters and punctuation. The others are used to encode control sequence and other special conditions.)

Question 4

The _____ command can restore a terminal to sane behavior.

Answer 4

reset. (Usually, when you’d like to use the command, you won’t even be able to see yourself type it. However, if at an unreadable bash prompt, blindly typing reset and followed by the RETURN key will usually restore the terminal to sane behavior.)

Question 5

Linux terminals share a lot in common with their primitive ancestors, teletypes and “dumb” or vt100-like consoles. These early devices had mechanisms for sending “out of band” signals, or sequences that signaled some event outside of the normal flow of type characters, such as a backspace, a linefeed, an audible bell, or an end of transmission. Linux terminals, like their predecessors, use the _____ key to send these “out of band” signals.

Answer 5

CTRL.

Question 6

CTRL+C (SIGNT)

Answer 6

Abnormal Interrupt - terminate the foreground process.

Question 7

CTRL+D (EOT)

Answer 7

Normal signaling of the end of input.

Question 8

CTRL+G (BEL)

Answer 8

Sound an audible terminal bell.

Question 9

CTRL+H (BS)

Answer 9

Backspace - erase the previous character

Question 10

CTRL+J (LF)

Answer 10

Line feed - alternative for the RETURN key

Question 11

CTRL+L (FF)

Answer 11

Form feed - causes bash to clear screen, and other screen based programs to “refresh” the current screen.

Question 12

CTRL+Q

Answer 12

Thaw the terminal display (see CTRL+S)

Question 13

CTRL+S

Answer 13

Freeze the terminal display (thaw with CTRL+Q)

Question 14

CTRL+U (NAK)

Answer 14

Erase current line

Question 15

CTRL+Z (SIGSTOP)

Answer 15

Suspend the foreground process.

Question 16

CTRL+C is probably the most useful of the above sequences, coming to the rescue whenever a user is felling “JUST MAKE IT STOP!” When using the bash shell, typing CTRL+C will….?

Answer 16

Terminate the currently running process, and return you to the bash prompt.

Question 17

The /dev/zero device node is a pseudo device that, when read…?

Answer 17

returns an infinite number of (binary) zeros.

Question 18

The /dev/null device node is a pseudo device that throws away any…?

Answer 18

information written to it.

Question 19

/dev/zero > /dev/null would…?

Answer 19

run forever, reading zeros and throwing them away. (Someone stuck in this situation could use CTRL+C to cancel the command)

Question 20

CTRL+D is used to send…?

Answer 20

an “End of Transmission” (usually interpreted as “End of File”) to the listening process.

Question 21

The wc command is an example of a command that, when not given a filename as an argument, will count the number of lines, words, and characters that a user types in from the keyboard. The user signals the end of the input with…?

Answer 21

CTRL+D

Question 22

When using the wc command what would happen if we used CTRL+C…?

Answer 22

The wc command would have been canceled, not reporting any output.

Question 23

CTRL+Z is used to…?

Answer 23

Suspend a program, (Which can later be restored with the fg (“forground”) command.

Question 24

While in the middle of an ftp session, how do you view the current working directory..?

Answer 24

Suspend the ftp session with CTRL+Z, run the pwd command from the shell, then restore the ftp session using fg.

Question 25

CTRL+U is commonly used to…?

Answer 25

“Wipe” the current line. (So if you have a mangled bash command line that you just want to start over, type CTRL+U. Also, CTRL+U is very helpful when you mess up entering a password. Because your characters are usually not echoed bach to you, its often hard to know what you’ve type. Just type CTRL+U and start over.)

Question 26

CTRL+H serves the same role as …?

Answer 26

BACKSPACE key. (On some terminals however, BACKSPACE key is incorrectly mapped, and doesn’t function correctly. CTRL+H will almost always work in these situations.)

Question 27

CTRL+L was traditionally used to tell a line printer to eject…?

Answer 27

the current page and start on the next one.

Question 28

CTRL+L for online terminals, has been re purposed for…?

Answer 28

redrawing screens.

Question 29

When using a screen based program, including the vi and nano editors, if the screen ever becomes mangled because of unexpected messages, CTRL+L will cause the program…?

Answer 29

to refresh the screen, redrawing it correctly.

Question 30

For bash shell, CTRL+L causes…?

Answer 30

bash to clear the screen, but preserve the current command line.

Question 31

CTRL+G, the only real use is to…?

Answer 31

make the terminal beep, impressing your friends with your vast reservoirs of Unix knowledge.

Question 32

Processes are grouped into…?

Answer 32

“sessions” based on which terminal they were started from. (While somewhat outdated, knowing how to recognize terminals can help in tracking the origins of processes.)

Question 33

Programs interact with terminals at…?

Answer 33

a low level through device nodes, found within the /dev directory. (For example, communication with the first virtual console uses the devices node /dev/tty1. Most processes keep a record of which terminal they were started from, and user’s login sessions are usually associated with the terminal they are using. When identifying terminals in these situations, the terminal is referred to by its device node, for example, tty1)

Question 34

Many different devices are treated by Linux as a terminal, including…?

Answer 34

Virtual consoles, serial line connected VT100 terminals, modems, etc.

Question 35

ttyn (Virtual Console)

Answer 35

Accessed with the CTRL+ALT+Fn key combination.

Question 36

ttySn (Serial port device)

Answer 36

A modem or VT100 like terminal attached to a serial port. The terminal ttyS0 in Unix relates to COM1 in DOS, ttyS1 to COM2, and so on.

Question 37

pts/n (Pseudo-terminal)

Answer 37

A terminal emulation, most often used by terminal windows in the X graphical environment, or shells which originate over the network, such as with the telnet or ssh. Pseudo-terminals cannot be related directly to a physical device.

Question 38

:0 (X server)

Answer 38

The X server environment is not really a terminal. When a user logs in using the X graphical environment, their terminal may be listed as the X server itself.

Question 39

When typing the names of commands and files, a lot of time and effort can be saved by learning how to make good use of the …?

Answer 39

TAB key

Question 40

When typing the name of a command as the first word of a bash command line, start typing the command you would like to run, but at some point before you finish the word, stop and hit the TAB key. One of three things will happen….

Answer 40

• The rest of the command you were beginning to type magically appears.
• Part of the command you were typing magically appears, but then bash stops and beeps at you.
• bash just beeps at you.

Question 41

The bash shell does the best job that it can in selecting the command you were starting to type from…?

Answer 41

the list of all possible commands.

Question 42

If when pushing the Tab key, the rest of the command magically appears, the bash was able to…?

Answer 42

figure out exactly what command you were starting, and finished it for you.

Question 43

When after pushing tab, part of the command you were typing magically appears, but then bash stops and beeps at you…?

Answer 43

more than one command started out with the letters you were typing. bash completed the command as far as possible, but stopped with a beep to let you know that you still have some choices to make. In order to see the selection of commands that bash has narrowed it down to, hit the TAB key a second time. bash will list all commands that start with what you have typed. Supply enough of the remainder of the command to make it unique, and hit TAB again. bash will finish the command for you.

Question 44

When you push tab, bash just beeps at you…?

Answer 44

more than one command started out with the letters you were typing. bash completed the command as far as possible, but stopped with a beep to let you know that you still have some choices to make. In order to see the selection of commands that bash has narrowed it down to, hit the TAB key a second time. bash will list all commands that start with what you have typed. Supply enough of the remainder of the command to make it unique, and hit TAB again. bash will finish the command for you.