Shell Scripting

Question 1

What should the first line be in a bash script?

Answer 1

#!/bin/bash
*the shebang as the first line in the script tells bash what scripting language is being used

Question 2

How do you run a script without specifying a path, and calling like a native command?

Answer 2

Move script to one of the directories contained within the $PATH env variable
i.e /home//bin

Question 3

How do you evaluate (run) a command in quotation marks?

Answer 3

$()

i. e echo “$(ls)”
* `` - legacy: i.e ls will substitute value of ls

Question 4

How do you make a script executable?

Answer 4

chmod +x scriptname

Question 5

How do you write an if statement in bash?

Answer 5

if [ ]; then
>command<
fi

Question 6

How do you write an if else statement in bash?

Answer 6

if [  ]; then
    >command<
else
    >command<
fi

Question 7

How do you write a for loop in bash?

Answer 7

for i in {1..10}
do
echo “$i”
done

Question 8

In bash, what is the stored variable containing the number of arguments the script was run with?

Answer 8

$#

Question 9

In bash, what is the stored variable that contains the scripts own filename?

Answer 9

$0

Question 10

In bash, what is the stored variable containing script arguments?

Answer 10

$1..$n

Question 11

What is an alternative way to write a variable within quotes?

Answer 11

${}
i.e var=tree
echo "${var}s"
*useful for string seperation
"$vars" won't work

Question 12

How do you write a function in a bash script?

Answer 12

function multiply() {
     echo 5 * $1
}
*call function
multiply 2

Question 13

How do you run a command sequentially after another?

Answer 13

;

i.e pwd; ls

Question 14

How do you run a command sequentially only if the first was successful?

Answer 14

&&

i.e ls -lh file && cat file

Question 15

How do you run a command sequentially only if the first was unsuccessful?

Answer 15

||

i.e ls nonexistant || touch nonexistant