Variables & Loops

Let's write a simple script to automate creating a new ESP32 project folder. This will introduce variables, user input, and conditionals.

Your First Script

Create a new file named create_project.sh and add the following code:

#!/bin/bash

# 1. Variables
# Note: DO NOT put spaces around the equals sign!
PROJECT_DIR="my_esp_projects"

# 2. Print to screen
echo "Starting project setup..."

# 3. Create the directory
mkdir -p $PROJECT_DIR

# 4. Navigate into it
cd $PROJECT_DIR

echo "Done! You are now in $PROJECT_DIR."

Making it Executable

Before you can run it, you must give the file execute permissions:

chmod +x create_project.sh

Now, run it:

./create_project.sh

(We use ./ to tell the shell "run the file that is located right here in the current directory").

Taking User Input

Scripts are more powerful when they are interactive. We use the read command to pause the script and wait for the user to type something.

#!/bin/bash

echo "What is the name of your new project?"
read PROJECT_NAME

echo "Creating folder for $PROJECT_NAME..."
mkdir -p $PROJECT_NAME

Conditionals (if statements)

Sometimes you only want to execute a command if a certain condition is met. For example, check if a file already exists before trying to download it.

#!/bin/bash

FILE="esp-idf-v5.1.zip"

# -f checks if the file exists
if [ -f "$FILE" ]; then
    echo "$FILE already exists. Skipping download."
else
    echo "Downloading $FILE..."
    # wget https://...
fi

(Notice the spaces inside the [ ] brackets. They are strictly required in Bash!)

Loops

If you need to perform the same action on multiple files, use a for loop.

#!/bin/bash

# Loop over three specific chip names
for CHIP in esp32 esp32s2 esp32s3
do
    echo "Compiling firmware for target: $CHIP"
    # idf.py set-target $CHIP
    # idf.py build
done

Looping Over Files

You can also loop over all files matching a pattern in a directory:

#!/bin/bash

# Find all .txt files and rename them to .log
for file in *.txt
do
    mv "$file" "${file%.txt}.log"
done

You now have the foundation to read and understand the setup scripts often provided with embedded SDKs!