Shell and Command Line Basics

Question 1

internal command

Answer 1

command within your shell, part of the shell

Question 2

external command

Answer 2

stored as separate binaries, started with a sub-process

Question 3

PATH

Answer 3

environment variable storing a list of directories in which commands can be found

Question 4

change PATH variable by editing…

Answer 4

shell config file

Question 5

required to run programs which don’t exist in PATH

Answer 5

complete path of the utility

Question 6

command completion

Answer 6

type part of a command or filename and press Tab key for completion
- displays result or possible results

Question 7

history

Answer 7

• record of typed commands
• stored in /bash_history
• up and down arrow keys

Question 8

historical search

Answer 8

• ctrl+R to begin a reverse search
• ctrl+S is a forward search
• ctrl+G terminate search

Question 9

movement

Answer 9

• ctrl+A start of line
• ctrl+E end of line
• ctrl+left or right arrows move by one word

Question 10

delete text

Answer 10

• ctrl+D or delete key deletes character under cursor
• backspace deletes character to the left of cursor
• ctrl+K deletes all text from cursor to end of line
• ctrl+X, backspace deletes all text from cursor to start of line

Question 11

invoke an editor

Answer 11

• ctrl-X, ctrl+E

- launches an editor defined by FCEDIT or EDITOR environment variables

Question 12

main global config files for shell

Answer 12

• ~/.bashrc

- ~/.profile

Question 13

~ directory

Answer 13

your home directory

Question 14

environment variables

Answer 14

value references which can be shared by different programs within an environment

Question 15

set environment variable

Answer 15

• know name of env var
• use assignment operator (=)
• export variable
  (i. e. export NNTPSERVER=new.abigisp.com)

Question 16

$ identifier

Answer 16

identifies a variable (i.e. echo $PATH)

Question 17

command env

Answer 17

view entire environment of variables

Question 18

command unset

Answer 18

• remove environment variable

- syntax: unset [variableName]

Question 19

command man

Answer 19

• text-based system known as man, for manual

- syntax: man [programName]

Question 20

less pager

Answer 20

• displays information
• spacebar to move forward by a page
• esc followed by V to move back a page
• arrow keys move up or down line by line
• / key to search for text
• q key to exit

Question 21

command info

Answer 21

• info pages which allow hypertext format

- syntax: info [program]

Question 22

stream

Answer 22

data entity that can be manipulated

Question 23

standard input stream

Answer 23

stdin input typically from a keyboard

Question 24

standard output stream

Answer 24

stdout, normally displayed on screen

Question 25

standard error stream

Answer 25

- stderr, carry high-priority info such as error messages | - typically sent to stdout

Question 26

> redirection

Answer 26

creates a new file containing stdout, overwriting if necessary

Question 27

>> redirection

Answer 27

appends stdout to existing file, creating if necessary

Question 28

2> redirection

Answer 28

creates a new file containing stderr, overwriting if necessary

Question 29

2>> redirection

Answer 29

appends stderr to existing file, creating if necessary

Question 30

&> redirection

Answer 30

creates a new file containing both stdout and stderr, overwriting if necessary

Question 31

< redirection

Answer 31

sends contents of file as stdin

Question 32

<< redirection

Answer 32

accepts text on following lines as stdin

Question 33

<> redirection

Answer 33

causes specified file to be used for both stdin and stdout

Question 34

stdin number

Answer 34

0

Question 35

stdout number

Answer 35

1

Question 36

sterr number

Answer 36

2

Question 37

null device

Answer 37

/dev/null | potentially usable to discard data

Question 38

tee

Answer 38

splits stdin to diplay on stdout and as many files as specified

Question 39

| operator

Answer 39

pipe

Question 40

piping

Answer 40

redirecting output from one program to the input of another program

Question 41

command cat

Answer 41

- concatenate files linking them together end to end into one file - typing one file will simply display that file in stdout

Question 42

command expand

Answer 42

convert tabs to spaces

Question 43

fmt command

Answer 43

reformat paragraphs

Question 44

command head

Answer 44

view beginning lines of a file

Question 45

command od

Answer 45

display files in Octal

Question 46

command od

Answer 46

display files in octal (base-8)

Question 47

command sort

Answer 47

sort files

Question 48

command split

Answer 48

break a file into pieces

Question 49

command tr

Answer 49

- translate characters | - syntax: tr [options] set1 set2

Question 50

command uniq

Answer 50

delete duplicate lines

Question 51

command nl

Answer 51

number lines

Question 52

command pr

Answer 52

prepare a plain-text file for printing

Question 53

comman tail

Answer 53

diplays lines at end of file

Question 54

command less

Answer 54

- read a file a screen at a time, paging back and forth through the file - spacebar pages forward - escape+V goes back a page

Question 55

command cut

Answer 55

extract portions of input lines and displat them on stdout

Question 56

command cut

Answer 56

extract portions of input lines and display them on stdout

Question 57

command wc

Answer 57

- displays word count as well as line and byte counts for a file - syntax: wc [fileName]

Question 58

regular expressions

Answer 58

express patterns in text

Question 59

[] regex

Answer 59

match any one character within brackets

Question 60

range regex

Answer 60

variant of bracket, matches any character within a range with a start and end point

Question 61

dot regex

Answer 61

matches any character

Question 62

^ regex

Answer 62

matches the start of a line

Question 63

$ regex

Answer 63

matches the end of a line

Question 64

* regex

Answer 64

matches zero or more occurrences

Question 65

+ regex

Answer 65

matches one or more occurrences

Question 66

| regex

Answer 66

vertical bar matches multiple possibilities (i.e. car|truck)

Question 67

() regex

Answer 67

denote subsection, think order of operations

Question 68

\ regex

Answer 68

escapes following character, literally matching the following character regardless if it is a special character

Question 69

command grep

Answer 69

- search through output | - syntax: grep [options] regexp [files]

Question 70

command sed

Answer 70

- modifying text - syntax: sed [options] -f script-file [input-file] sed [options] script-text [input-file] - script text is the set of commands sed should perform