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# User callback script

## Introduction

During the backup process, `Back In Time` can call a user defined script at different steps. This script is named `user-callback` and contained in the directory `$XDG_CONFIG_HOME/backintime`. By default `$XDG_CONFIG_HOME` is `~/.config`). It can also be configured via the GUI: Manage profiles > Options > Edit user-callback (see also Options tab in Manage profiles dialog).

## Script arguments

1. The profile id (1=Main Profile, ...).
2. Profile name.
3. Callback reason:

Value | Reason
--- | ---
1 | A backup process is about to start.
2 | A backup process has ended.
3 | A new backup was created. The following two extra arguments are backup ID and backup path.
4 | There was an error. See next table for error codes.
5 | The (graphical) application has started.
6 | The (graphical) application has closed.
7 | Mounting a filesystem for the profile may be necessary.
8 | Unmounting a filesystem for the profile may be necessary.

Possible error codes (see Callback reason 4) are:

Code | Error
--- | ---
1 | Configuration is either missing or invalid.
2 | A backup process is already running.1
3 | Can't find backups directory.2
4 | A backup for "now" already exists. The fifth argument is the backup ID.
5 | Error while creating a backup.3 The fifth argument contains more error information.
6 | New backup created but with errors.3 The fifth argument is the backup ID.

## Return value

The script should return `0` if the backup should continue, any value other than `0` will cancel the backup.

## Implementation

The `UserCallbackPlugin` is a class defined in `common/plugins/usercallbackplugin.py`. It is a child class of `Plugin` which you can be found in `common/pluginmanager.py`.

## Examples

Several example scripts can be found in the directory `/usr/share/doc/backintime` or in the projects repository.

The following is a minimal script to log all calls to user-callback to a file in `$HOME/.local/state/backintime_callback_log`.

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    #!/bin/bash
    # SPDX-FileCopyrightText: © 2024 Kosta Vukicevic
    # SPDX-FileCopyrightText: © 2024 @daveTheOldCoder
    # SPDX-License-Identifier: CC0-1.0

    LOG_FILE='/tmp/backintime_callback.log'

    # Get current time
    current_time=$(date +"%Y-%m-%d %H:%M:%S")

    # Check if file exists, if not create it
    touch $LOG_FILE

    # Append current time to the file
    echo -n "{$current_time}: " >> "$LOG_FILE"

    # Iterate through all arguments
    for arg in "$@"
    do
        # Append argument to the file
        echo -n "$arg," >> "$LOG_FILE"
    done

    # Append newline character at the end
    echo >> "$LOG_FILE"

1. Ensure that manual and automatic backups do not run at the same time. ↩

2. For example, if the backups directory is on a removable drive, which is either not mounted, or is mounted at a different location. ↩

3. Supported added in Back In Time version 1.4.0. ↩↩