# Answers to 'Loops' Exercises

Exercise 1: Variables in Loops
---
You can try this out using the following commands

```
touch fructose.dat glucose.dat sucrose.dat
for datafile in *.dat; do ls *.dat; done
```

it prints

```
fructose.dat    glucose.dat sucrose.dat
fructose.dat    glucose.dat sucrose.dat
fructose.dat    glucose.dat sucrose.dat
```

because each time `ls *.dat* displays all the files with a `.dat` extension.

```
for datafile in *.dat; do ls $datafile; done
```

prints

```
fructose.dat
glucose.dat
sucrose.dat
```

because each iteration of the loop prints one item in `*.dat` which expands to the three `.dat` files.

Exercise 2: Saving a file in a loop - Part One
---

Answer: 1. (Try it out to confirm) 


Exercise 3: Saving a file in a loop - Part Two
---
Answer: 1. (Try it out to confirm)


Exercise 4: Doing a dry run
---
Version 1 would echo analyze $file and save the result to the file analyzed-$file.  We would not see anything on the screen

Version 2 is the one we want and it would print the expanded string "analyze $file > analyzed-$file" to the console for each iteration of the for loop.


Exercise 5: Nested loops
---
Let's try it out and see

```
for sugar in fructose glucose sucrose
do
    for temperature in 25 30 37 40
    do
        mkdir $sugar-$temperature
    done
done
```

First, a sugar is extracts from [fructose, glucose, sugar]. For this sugar four directories are made that have the pattern $sugar-$temperature where $temperature is on of the 4 temps given.  This is repeated for each sugar so that 12 new directories are made.