clap-logflag

[work in progress]

The clap-logflag library adds a --log flag to clap based applications that allows CLI users to configure logging from the command line. It can log to stderr, files and syslog.

Examples

# Log to a single destination
$ ./your-cli --log syslog
$ ./your-cli --log file:/path/to/file

# Log to both stderr and a file
$ ./your-cli --log stderr --log file:/path/to/file

# Filter log levels
$ ./your-cli --log DEBUG:stderr --log INFO:file:/path/to/file

# Disable logging
$ ./your-cli --log none

# Use default logging setup (defined by the application developer)
$ ./your-cli

Setup

To use clap-logflag, first add clap-logflag, clap and log to your Cargo.toml.

Then, add the LogArgs struct to your clap definition and initialize logging with it:

use clap::Parser;
use clap_logflag::LoggingConfig;
use log::LevelFilter;

#[derive(Debug, Parser)]
struct CliArgs {
    // Use this to add the log flags to your application
    #[clap(flatten)]
    log: clap_logflag::LogArgs,
    
    // ... your other cli args ...
}

fn main() {
    let args = CliArgs::parse();

    // Initialize logging with the flags from clap
    clap_logflag::init_logging!(
        args.log
            // If no `--log` arguments are present, disable logging.
            // You can change this to define the default behavior,
            // see the "default_logging" example.
            .or_default(LoggingConfig::LoggingDisabled),
        // Any `--log` argument that doesn't define a level filter will use the
        // default level filter defined here, `Info` in this example.
        LevelFilter::Info,
    );

    // Issue some log messages
    log::trace!("Some trace log");
    log::debug!("Some debug log");
    log::info!("Some info log");
    log::warn!("Some warn log");
    log::error!("Some error log");
}

Syntax

See LogArgs for a detailed explanation of the syntax for the --log argument.

License: MIT OR Apache-2.0