Chapter 9 - Writing Scripts, Configuring Email, & Using Databases

Question 1

what do environmental variables provide?

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Answer 1

the means to pass named data to programs launched from a shell or a subshell

Question 2

what is a subshell?

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Answer 2

a child process that is created by either the shell or a shell script when a program is initiated

Question 3

you’ve set an environment variable manually via an equal-sign assignment operator. what command must you use to make that variable to subshells?

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Answer 3

the export command

Question 4

how can you find out how environment variables are configured? (what do you type?)

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Answer 4

env, set, or printenv

Question 5

if you want to know the value of one variable, you can use the echo command, but how do you use it?

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Answer 5

echo $variable

Question 6

tell me 3 times when you would use an alias

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Answer 6

1. to assign names that are easier to remember in order to obscure commands
2. to implement desirable command options as a command’s default
3. to create a shortened version of a command to minimize typing

Question 7

you are configuring shells via shell configuration files. tell me the 2 ways they are classified (4 combinations).

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Answer 7

whether they are global or user files and whether they have login or non-login file locations

Question 8

how can you see your current key bindings?

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Answer 8

bind -p

Question 9

true/false: most minux systems use bash by default

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Answer 9

true

Question 10

you are looking at a shell script. what tells the linux kernel that it is a shell script?

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Answer 10

it begins with a #!

Question 11

tell me 6 commands that are commonly used in scripts

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Answer 11

file manipulation commands (ls, mv, cp, rm)
grep
find
cut
sed
echo

Question 12

is it possible to set a script’s SUID (SGID bits)?

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Answer 12

yes

Question 13

when you type the script’s name, preceded by bash, what does that do?

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Answer 13

it tells linux to run the script in the current directory rather than searching the current path

Question 14

what is a script?

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Answer 14

a simple program written in an interpreted computer language that’s embedded in the linux shell, used for repetitive tasks

Question 15

typing the script’s name, preceded by ./, tells linux what?

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Answer 15

tells linux to run the script in the current directory rather than searching the current path

Question 16

when would you type the script’s full path and name?

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Answer 16

when the script is not located in your current working directory

Question 17

typing in the script’s names requires the shell script to be moved to what?

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Answer 17

moved to a directory on your path

Question 18

typing the script’s name, preceded by sh, does what?

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Answer 18

tells linux to run the script in the current directory rather than searching the current path

Question 19

what happens when you type the source keyword before the script name?

is a subshell created to run the script?

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Answer 19

it tells the bash shell to use a method type called sourcing.

no

Question 20

typing a dot and a space before the script name does what?

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Answer 20

tells the bash shell to use the sourcing method type

Question 21

what does exec ./ script-name do?

does it need execute permission set on the file?

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Answer 21

method for executing a file

yes

Question 22

when you are using variables in shell scripts, what is a variable?

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Answer 22

a placeholder in a script for a value that will be determined when the script runs

Question 23

variables that are passed to the script are frequently called what?

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Answer 23

positional parameters

Question 24

tell me two places where a user defined variable can be used.

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Answer 24

within a script

at the command line

Question 25

when do you use / not use the dollar sign with a variable (environment or user defined)?

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Answer 25

use the dollar sign if you’re doing anything WITH the variable, don’t use it if you’re doing anything TO the variable