bash-logger

A lightweight, reusable logging library for Bash scripts.

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Features

• Four log levels: DEBUG, INFO, WARN, ERROR
• Colored console output
• File logging with timestamps
• Automatic log archiving based on retention days
• Script duration and exit code footer in log files
• sudo-aware file ownership handling (no load-time side effects)
• Configurable via a simple .conf file
• Invalid MIN_LOG_LEVEL falls back to INFO with a warning

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Project Structure

your-project/
├── conf/
│   └── logger.conf
├── lib/
│   └── logger.sh
└── your-script.sh

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Setup

1. Copy lib/logger.sh and conf/logger.conf into your project following the structure above.

2. Source the library:

source ./lib/logger.sh

SCRIPT_DIR is auto-detected from the library location, so no need to set it manually. You can still override it if needed:

readonly SCRIPT_DIR="/path/to/your/project"
source "$SCRIPT_DIR/lib/logger.sh"

For accurate duration tracking in the footer, set START_TIME before sourcing the library:

readonly START_TIME=$(date +%s%3N)

If omitted, the footer shows N/A for duration.

3. Initialize the logger before any log calls:

logger_init

logger_init creates the log file, runs archiving, and registers a trap to automatically write the footer when the script exits. You do not need to call log_footer manually.

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Configuration

All settings live in conf/logger.conf.

Variable	Description	Example
softname	Name used in log filenames	myapp
environment	Environment tag in log filenames	dev, prod
LOG_DIR	Directory for log files	$SCRIPT_DIR/logs
ARCHIVE_DIR	Directory for archived logs	$SCRIPT_DIR/logs/archive
LOG_RETENTION_DAYS	Days before logs are archived	7
MIN_LOG_LEVEL	Minimum level to output	DEBUG, INFO, WARN, ERROR
SHOW_CONSOLE	Print logs to terminal	true / false
SHOW_FILE	Write logs to file	true / false
ENABLE_COLORS	Colorize console output	true / false
AUTO_ARCHIVE	Automatically archive old logs	true / false
AUTO_CHOWN	Fix log ownership when using sudo	true / false
LOG_DATE_FORMAT	Timestamp format	%Y-%m-%d %H:%M:%S
COLOR_DEBUG	ANSI color for DEBUG	\033[0;34m
COLOR_INFO	ANSI color for INFO	\033[0;32m
COLOR_WARN	ANSI color for WARN	\033[1;33m
COLOR_ERROR	ANSI color for ERROR	\033[0;31m
COLOR_RESET	ANSI reset code	\033[0m

Note: If MIN_LOG_LEVEL is set to an invalid value, the library prints a warning to stderr and falls back to INFO.

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Usage

log DEBUG "Detailed diagnostic info"
log INFO  "Service started on port 8080"
log WARN  "Disk usage above 80%"
log ERROR "Failed to connect to database"

Log level input is case-insensitive — log info "message" and log INFO "message" both work.

Log level filtering is controlled by MIN_LOG_LEVEL. For example, setting it to WARN will suppress DEBUG and INFO messages.

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Log Files

Log files are created automatically in LOG_DIR and named:

{softname}_{environment}_{YYYY-MM-DD}.log

For example: sample_dev_2026-02-18.log

Each log file includes a header on start and a footer on exit containing the timestamp, exit code, and total script duration.

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License

MIT