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certificates/essentials/lpi_essentials_lesson_03.md
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# Lesson 3.3.1 # Lesson 3.3.1
1. The user types the following to their shell: 1. The user types the following to their shell:
``` ```
$ PATH=~/scripts $ PATH=~/scripts
$ ls $ ls
Command 'ls' is available in '/bin/ls' Command 'ls' is available in '/bin/ls'
The command could not be located because '/bin' is not included in the PATH environment variable. The command could not be located because '/bin' is not included in the PATH environment variable.
ls: command not found ls: command not found
``` ```
* What has the user done? * What has the user done?
* What command will combine the current value of PATH with the new directory ~/scripts? * What command will combine the current value of PATH with the new directory ~/scripts?
1. Consider the following script. Notice that it is using elif to check for a second condition: 1. Consider the following script. Notice that it is using elif to check for a second condition:
``` ```
> /!bin/bash > /!bin/bash
> fruit1 = Apples > fruit1 = Apples
> fruit2 = Oranges > fruit2 = Oranges
if [ $1 -lt $# ] if [ $1 -lt $# ]
then then
echo "This is like comparing $fruit1 and $fruit2!" echo "This is like comparing $fruit1 and $fruit2!"
> elif [$1 -gt $2 ] > elif [$1 -gt $2 ]
then then
> echo '$fruit1 win!' > echo '$fruit1 win!'
else else
> echo "Fruit2 win!" > echo "Fruit2 win!"
> done > done
``` ```
* The lines marked with a > contain errors. Fix the errors. * The lines marked with a > contain errors. Fix the errors.
1. What will the output be in the following situations? 1. What will the output be in the following situations?
``` ```
$ ./guided1.sh 3 0 $ ./guided1.sh 3 0
$ ./guided1.sh 2 4 $ ./guided1.sh 2 4
$ ./guided1.sh 0 1 $ ./guided1.sh 0 1
``` ```
## Explorational Exercises ## Explorational Exercises
1. Write a simple script that will check if exactly two arguments are passed. If so, print the arguments in reverse order. Consider this example (note: your code may look different than this, but should lead to the same output): 1. Write a simple script that will check if exactly two arguments are passed. If so, print the arguments in reverse order. Consider this example (note: your code may look different than this, but should lead to the same output):
``` ```
if [ $1 == $number ] if [ $1 == $number ]
then then
echo "True!" echo "True!"
fi fi
``` ```
1. This code is correct, but it is not a number comparison. Use an internet search to discover how this code is different from using -eq. 1. This code is correct, but it is not a number comparison. Use an internet search to discover how this code is different from using -eq.
1. There is an environment variable that will print the current directory. Use env to discover the name of this variable. 1. There is an environment variable that will print the current directory. Use env to discover the name of this variable.
1. Using what you have learned in questions 2 and 3, write a short script that accepts an argument. If an argument is passed, check if that argument matches the name of the current directory. If so, print yes. Otherwise, print no. 1. Using what you have learned in questions 2 and 3, write a short script that accepts an argument. If an argument is passed, check if that argument matches the name of the current directory. If so, print yes. Otherwise, print no.
@ -125,7 +125,6 @@ fi
## Guided Exercises ## Guided Exercises
1. Read the contents of script1.sh below: 1. Read the contents of script1.sh below:
``` ```
#!/bin/bash #!/bin/bash
@ -145,9 +144,7 @@ fi
echo "here's your cake!" echo "here's your cake!"
exit 0 exit 0
``` ```
* What is the output of these commands? * What is the output of these commands?
``` ```
./script1.sh ./script1.sh
echo $? echo $?