This is a tool to download submissions or submission data from Reddit. It can be used to archive data or even crawl Reddit to gather research data. The BDFR is flexible and can be used in scripts if needed through an extensive command-line interface.
If you wish to open an issue, please read [the guide on opening issues](docs/CONTRIBUTING.md#opening-an-issue) to ensure that your issue is clear and contains everything it needs to for the developers to investigate.
The BDFR works by taking submissions from a variety of "sources" from Reddit and then parsing them to download. These sources might be a subreddit, multireddit, a user list, or individual links. These sources are combined and downloaded to disk, according to a naming and organisational scheme defined by the user.
There are two modes to the BDFR: download, and archive. Each one has a command that performs similar but distinct functions. The `download` command will download the resource linked in the Reddit submission, such as the images, video, etc. The `archive` command will download the submission data itself and store it, such as the submission details, upvotes, text, statistics, as and all the comments on that submission. These can then be saved in a data markup language form, such as JSON, XML, or YAML.
- Note that this limit applies to **each source individually** e.g. if a `--limit` of 10 and three subreddits are provided, then 30 total submissions will be scraped
The following options apply only to the `download` command. This command downloads the files and resources linked to in the submission, or a text submission itself, to the disk in the specified directory.
The BDFR uses OAuth2 authentication to connect to Reddit if authentication is required. This means that it is a secure, token-based system for making requests. This also means that the BDFR only has access to specific parts of the account authenticated, by default only saved posts, upvoted posts, and the identity of the authenticated account. Note that authentication is not required unless accessing private things like upvoted posts, saved posts, and private multireddits.
To authenticate, the BDFR will first look for a token in the configuration file that signals that there's been a previous authentication. If this is not there, then the BDFR will attempt to register itself with your account. This is normal, and if you run the program, it will pause and show a Reddit URL. Click on this URL and it will take you to Reddit, where the permissions being requested will be shown. Read this and **confirm that there are no more permissions than needed to run the program**. You should not grant unneeded permissions; by default, the BDFR only requests permission to read your saved or upvoted submissions and identify as you.
If the permissions look safe, confirm it, and the BDFR will save a token that will allow it to authenticate with Reddit from then on.
Most users will not need to do anything extra to use any of the current features. However, if additional features such as scraping messages, PMs, etc are added in the future, these will require additional scopes. Additionally, advanced users may wish to use the BDFR with their own API key and secret. There is normally no need to do this, but it *is* allowed by the BDFR.
The configuration file for the BDFR contains the API secret and key, as well as the scopes that the BDFR will request when registering itself to a Reddit account via OAuth2. These can all be changed if the user wishes, however do not do so if you don't know what you are doing. The defaults are specifically chosen to have a very low security risk if your token were to be compromised, however unlikely that actually is. Never grant more permissions than you absolutely need.
The naming and folder schemes for the BDFR are both completely customisable. A number of different fields can be given which will be replaced with properties from a submission when downloading it. The scheme format takes the form of `{KEY}`, where `KEY` is a string from the below list.
Each of these can be enclosed in curly bracket, `{}`, and included in the name. For example, to just title every downloaded post with the unique submission ID, you can use `{POSTID}`. Static strings can also be included, such as `download_{POSTID}` which will not change from submission to submission. For example, the previous string will result in the following submission file names:
At least one key *must* be included in the file scheme, otherwise an error will be thrown. The folder scheme however, can be null or a simple static string. In the former case, all files will be placed in the folder specified with the `directory` argument. If the folder scheme is a static string, then all submissions will be placed in a folder of that name. In both cases, there will be no separation between all submissions.
It is highly recommended that the file name scheme contain the parameter `{POSTID}` as this is **the only parameter guaranteed to be unique**. No combination of other keys will necessarily be unique and may result in posts being skipped as the BDFR will see files by the same name and skip the download, assuming that they are already downloaded.
The configuration files are, by default, stored in the configuration directory for the user. This differs depending on the OS that the BDFR is being run on. For Windows, this will be:
The logging output for each run of the BDFR will be saved to this directory in the file `log_output.txt`. If you need to submit a bug, it is this file that you will need to submit with the report.
The `config.cfg` is the file that supplies the BDFR with the configuration to use. At the moment, the following keys **must** be included in the configuration file supplied.
All of these should not be modified unless you know what you're doing, as the default values will enable the BDFR to function just fine. A configuration is included in the BDFR when it is installed, and this will be placed in the configuration directory as the default.
Most of these values have to do with OAuth2 configuration and authorisation. The key `backup_log_count` however has to do with the log rollover. The logs in the configuration directory can be verbose and for long runs of the BDFR, can grow quite large. To combat this, the BDFR will overwrite previous logs. This value determines how many previous run logs will be kept. The default is 3, which means that the BDFR will keep at most three past logs plus the current one. Any runs past this will overwrite the oldest log file, called "rolling over". If you want more records of past runs, increase this number.
The option `max_wait_time` has to do with retrying downloads. There are certain HTTP errors that mean that no amount of requests will return the wanted data, but some errors are from rate-limiting. This is when a single client is making so many requests that the remote website cuts the client off to preserve the function of the site. This is a common situation when downloading many resources from the same site. It is polite and best practice to obey the website's wishes in these cases.
To this end, the BDFR will sleep for a time before retrying the download, giving the remote server time to "rest". This is done in 60 second increments. For example, if a rate-limiting-related error is given, the BDFR will sleep for 60 seconds before retrying. Then, if the same type of error occurs, it will sleep for another 120 seconds, then 180 seconds, and so on.
The option `--max-wait-time` and the configuration option `max_wait_time` both specify the maximum time the BDFR will wait. If both are present, the command-line option takes precedence. For instance, the default is 120, so the BDFR will wait for 60 seconds, then 120 seconds, and then move one. **Note that this results in a total time of 180 seconds trying the same download**. If you wish to try to bypass the rate-limiting system on the remote site, increasing the maximum wait time may help. However, note that the actual wait times increase exponentially if the resource is not downloaded i.e. specifying a max value of 300 (5 minutes), can make the BDFR pause for 15 minutes on one submission, not 5, in the worst case.
