Function Libraries: Share Functions

Function libraries are files with functions. Source them. Use them.

Here's the thing: Libraries let you reuse functions. Write once. Use everywhere.

Creating Libraries

# lib.sh
function log_info() {
    echo "[INFO] $1"
}

function log_error() {
    echo "[ERROR] $1" >&2
}

My take: Libraries are just files with functions. Simple.

Using Libraries

#!/bin/bash
source lib.sh

log_info "Starting"
log_error "Failed"

My take: source loads library. Then use functions.

Common Patterns

Utility Library

# utils.sh
function is_file() {
    [ -f "$1" ]
}

function is_dir() {
    [ -d "$1" ]
}

Using It

source utils.sh

if is_file "test.txt"; then
    echo "File exists"
fi

Common Mistakes (I've Made These)

1. Not sourcing: Source libraries before use. Don't forget.

2. Circular dependencies: Libraries depending on each other. Avoid it.

3. Not organizing: Organize libraries. Group related functions.

What's Next?

Now that you understand libraries, you can build reusable code. Or review Functions to reinforce.

---

Personal note: Libraries seemed complex at first. Then I learned: just source files. Now I use them constantly. They're useful. Use them.