Function uucore::backup_control::determine_backup_mode

pub fn determine_backup_mode(matches: &ArgMatches<'_>) -> UResult<BackupMode>

Determine the “mode” for the backup operation to perform, if any.

Parses the backup options according to the GNU manual, and converts them to an instance of BackupMode for further processing.

Takes clap::ArgMatches as argument which must contain the options from arguments::backup() and arguments::backup_no_args(). Otherwise the NoBackup mode is returned unconditionally.

It is recommended for anyone who would like to implement the backup-functionality to use the arguments prepared in the arguments submodule (see examples)

Errors

If an argument supplied directly to the long backup option, or read in through the VERSION CONTROL env var is ambiguous (i.e. may resolve to multiple backup modes) or invalid, an InvalidArgument or AmbiguousArgument error is returned, respectively.

Examples

Here’s how one would integrate the backup mode determination into an application.

#[macro_use]
extern crate uucore;
use uucore::backup_control::{self, BackupMode};
use clap::{App, Arg, ArgMatches};

fn main() {
    let matches = App::new("app")
        .arg(backup_control::arguments::backup())
        .arg(backup_control::arguments::backup_no_args())
        .get_matches_from(vec![
            "app", "-b", "--backup=t"
        ]);

    let backup_mode = backup_control::determine_backup_mode(&matches).unwrap();
    assert_eq!(backup_mode, BackupMode::NumberedBackup)
}

This example shows an ambiguous input, as ‘n’ may resolve to 4 different backup modes.

#[macro_use]
extern crate uucore;
use uucore::backup_control::{self, BackupMode, BackupError};
use clap::{App, Arg, ArgMatches};

fn main() {
    let matches = App::new("app")
        .arg(backup_control::arguments::backup())
        .arg(backup_control::arguments::backup_no_args())
        .get_matches_from(vec![
            "app", "-b", "--backup=n"
        ]);
    
    let backup_mode = backup_control::determine_backup_mode(&matches);

    assert!(backup_mode.is_err());
    let err = backup_mode.unwrap_err();
    // assert_eq!(err, BackupError::AmbiguousArgument);
    // Use uucore functionality to show the error to the user
    show!(err);
}