bash-functions

This is a Bash shell library that provides a set of common utility functions to ease and streamline the scripting process in Debian-like environments.

Function Reference

1. set_colors

Initializes color variables for terminal text formatting.

Parameters: None

Example:

set_colors
echo -e "${GREEN}Success!${NC}"

Available colors: GREEN, RED, YELLOW, BLUE, NC (No Color), BOLD, UNDERLINE

---

2. backup_file

Creates a timestamped backup of a file if it exists.

Parameters:

• $1 - The path to the file to backup

Example:

backup_file "/etc/config.conf"
# Creates: /etc/config.conf.bak.20240206123045

---

3. is_silent

Checks if the first parameter is 'silent' to determine if output should be suppressed.

Parameters:

• $1 - (Optional) Pass "silent" to return true

Returns: 0 if silent, 1 otherwise

Example:

if is_silent "$1"; then
    echo "Running in silent mode"
fi

---

4. is_this_linux

Verifies that the script is running on a Linux distribution.

Parameters: None

Exits: With code 1 if not running on Linux

---

5. is_this_os_64bit

Verifies that the system is running a 64-bit operating system.

Parameters: None

Exits: With code 1 if not 64-bit

---

6. check_rpi_model

Checks if running on a Raspberry Pi and verifies minimum model requirement.

Parameters:

• $1 - The minimal Raspberry Pi model number required

Example:

check_rpi_model 4  # Requires Raspberry Pi 4 or higher

---

7. check_user_privileges

Verifies that the script is running with the correct user privileges.

Parameters:

• $1 - Either "privileged" (must be root) or "regular" (must not be root)

Example:

check_user_privileges "privileged"  # Requires root
check_user_privileges "regular"     # Requires non-root

---

8. check_apt

Verifies that the 'apt' package manager is available.

Parameters: None

Exits: With code 1 if apt is not installed

---

9. update_os

Updates the operating system using apt package manager.

Parameters:

• $1 - (Optional) Pass "silent" to suppress output

Example:

update_os          # Verbose mode
update_os silent   # Silent mode

---

10. install_packages

Installs one or more packages using apt package manager.

Parameters:

• $1 - (Optional) Pass "silent" as first argument to suppress output
• $@ - Package names to install

Example:

install_packages nginx mysql-server php
install_packages silent nginx mysql-server php

---

11. set_timezone

Sets the system timezone.

Parameters:

• $1 - Valid timezone (e.g., "Europe/Amsterdam")

Example:

set_timezone "Europe/Amsterdam"
set_timezone "America/New_York"

---

12. require_tool

Checks for required tools and exits if any are missing.

Parameters:

• $@ - Names of commands/tools to check for

Example:

require_tool git curl wget

---

13. validate_input

Validates input based on a specified type.

Parameters:

• $1 - The input value to validate
• $2 - The type of the variable: "y/n", "num", "str", "email", or "host"
• $3 - The name of the variable (used for error messages)

Returns: 0 if the input is valid, 1 otherwise.

Example:

if validate_input "yes" "y/n" "CONFIRMATION"; then
    echo "Valid input"
else
    echo "Invalid input"
fi

---

14. ask_user

Prompts the user for input with validation and default values. The function follows two paths:

1. Environment Variable Path: If an environment variable with the same name as the variable is set, its value is used directly. The value is validated, and if it is invalid, the script exits immediately with an error message.

2. User Input Path: If no environment variable is set, the user is prompted for input. The function re-asks the question until valid input is provided.

This ensures that the script can operate non-interactively when environment variables are pre-set, while still enforcing validation.

Parameters:

• $1 - Variable name to store the result
• $2 - Default value if user presses Enter
• $3 - Prompt message to display
• $4 - (Optional) Validation type: "y/n", "num", "str", "email", or "host" (default: "str")

Example:

ask_user "USERNAME" "admin" "Enter username" "str"
ask_user "PORT" "8080" "Enter port number" "num"
ask_user "ENABLE_SSL" "y" "Enable SSL?" "y/n"
ask_user "EMAIL" "admin@example.com" "Enter email" "email"
ask_user "HOSTNAME" "server.local" "Enter hostname" "host"

---

14. download_file

Downloads files using curl with error handling and optional backup.

Single file mode:

download_file URL DEST DESCRIPTION [backup]

Multi-file mode:

download_file -m DEST_DIR DESCRIPTION [backup] URL1:FILENAME1 URL2:FILENAME2

Examples:

# Single file
download_file "http://example.com/config.txt" "/etc/app/config.txt" "config file"

# Single file with backup
download_file "http://example.com/config.txt" "/etc/app/config.txt" "config file" backup

# Multiple files
download_file -m "/opt/app" "library files" \
  "http://example.com/lib1.so:lib1.so" \
  "http://example.com/lib2.so:lib2.so"

# Multiple files with backup
download_file -m "/opt/app" "library files" backup \
  "http://example.com/lib1.so:lib1.so" \
  "http://example.com/lib2.so:lib2.so"

How to Use

These functions can be imported and used in your own Bash scripts. To import the functions, use the following lines in your script:

# Remove old functions libraries and download the latest version
rm -f /tmp/functions.sh
if ! curl -s -o /tmp/functions.sh https://raw.githubusercontent.com/oszuidwest/bash-functions/main/common-functions.sh; then
  echo -e "*** Failed to download functions library. Please check your network connection! ***"
  exit 1
fi

# Source the functions file
source /tmp/functions.sh

And use it like this:

# Example
set_colors
echo -e "${GREEN}This text is green!${NC}"

To check for required tools:

require_tool git curl wget

Or this to ask the user for input, set a default (n) and validate the input (it should be y or n)

ask_user "SSL" "n" "Do you want Let's Encrypt to get a certificate for this server? (y/n)" "y/n"

All functions are documented inline with their parameters.

Note

This script should be run on a Unix-like system, such as Linux, that uses the Bash shell and 'apt' package manager. Certain functions specifically check for these conditions and will exit if they are not met.

Always ensure to use the correct permissions when running scripts that import these functions. For instance, functions like update_os and install_packages should be run with root permissions.

Be aware that the ask_user function does not just prompt the user for input, but also assigns the input to a variable. The name of the variable is passed as the first argument, and the function uses the eval command to assign the input to it. It's important to only pass safe, pre-defined strings as the first argument.

License

This project is licensed under the MIT License - see the LICENSE.md file for details.

Bugs, feedback, and ideas are welcome at techniek@zuidwesttv.nl or through pull requests.