neulab/tldr huggingface dataset:
--dht-message-timeout=<SEC> Set timeout in seconds. Default: 10
--enable-dht [true|false] Enable IPv4 DHT functionality. It also enables UDP tracker support. If a private flag is set in a torrent, aria2 doesn't use DHT for that download even if true is given.  Default: true
--enable-dht6 [true|false] Enable IPv6 DHT functionality. If a private flag is set in a torrent, aria2 doesn't use DHT for that download even if true is given. Use --dht-listen-port option to specify port number to listen on. See also --dht-listen-addr6 option.
--enable-peer-exchange [true|false] Enable Peer Exchange extension. If a private flag is set in a torrent, this feature is disabled for that download even if true is given.  Default: true
--follow-torrent=true|false|mem If true or mem is specified, when a file whose suffix is .torrent or content type is application/x-bittorrent is downloaded, aria2 parses it as a torrent file and downloads files mentioned in it. If mem is specified, a torrent file is not written to the disk, but is just kept in memory.  If false is specified, the .torrent file is downloaded to the disk, but is not parsed as a torrent and its contents are not downloaded.  Default: true
-O, --index-out=<INDEX>=<PATH> Set file path for file with index=INDEX. You can find the file index using the --show-files option.  PATH is a relative path to the path specified in --dir option. You can use this option multiple times. Using this option, you can specify the output file names of BitTorrent downloads.
--listen-port=<PORT>... Set TCP port number for BitTorrent downloads.  Multiple ports can be specified by using ,,  for example: 6881,6885.  You can also use - to specify a range: 6881-6999.  , and - can be used together: 6881-6889,6999.  Default: 6881-6999
NOTE: Make sure that the specified ports are open for incoming TCP traffic.
--max-overall-upload-limit=<SPEED> Set max overall upload speed in bytes/sec.  0 means unrestricted. You can append K or M (1K = 1024, 1M = 1024K).  To limit the upload speed per torrent, use --max-upload-limit option.  Default: 0
-u, --max-upload-limit=<SPEED> Set max upload speed per each torrent in bytes/sec.  0 means unrestricted.  You can append K or M (1K = 1024, 1M = 1024K).  To limit the overall upload speed, use --max-overall-upload-limit option.  Default: 0
--peer-id-prefix=<PEER_ID_PREFIX> Specify the prefix of peer ID. The peer ID in BitTorrent is 20 byte length. If more than 20 bytes are specified, only first 20 bytes are used. If less than 20 bytes are specified, random byte data are added to make its length 20 bytes.
Default: A2-$MAJOR-$MINOR-$PATCH-, $MAJOR, $MINOR and $PATCH are replaced by major, minor and patch version number respectively. For instance, aria2 version 1.18.8 has prefix ID A2-1-18-8-.
--peer-agent=<PEER_AGENT> Specify the string used during the bitorrent extended handshake for the peer's client version.
Default: aria2/$MAJOR.$MINOR.$PATCH, $MAJOR, $MINOR and $PATCH are replaced by major, minor and patch version number respectively. For instance, aria2 version 1.18.8 has peer agent aria2/1.18.8.
--seed-ratio=<RATIO> Specify share ratio. Seed completed torrents until share ratio reaches RATIO.  You are strongly encouraged to specify equals or more than 1.0 here.  Specify 0.0 if you intend to do seeding regardless of share ratio.  If --seed-time option is specified along with this option, seeding ends when at least one of the conditions is satisfied.  Default: 1.0
--seed-time=<MINUTES> Specify seeding time in (fractional) minutes. Also see the --seed-ratio option.
NOTE: Specifying --seed-time=0 disables seeding after download completed.
-T, --torrent-file=<TORRENT_FILE> The path to the ".torrent" file.  You are not required to use this option because you can specify ".torrent" files without --torrent-file.
Metalink Specific Options --follow-metalink=true|false|mem If true or mem is specified, when a file whose suffix is .meta4 or .metalink or content type of application/metalink4+xml or application/metalink+xml is downloaded, aria2 parses it as a metalink file and downloads files mentioned in it.  If mem is specified, a metalink file is not written to the disk, but is just kept in memory.  If false is specified, the .metalink file is downloaded to the disk, but is not parsed as a metalink file and its contents are not downloaded.  Default: true
--metalink-base-uri=<URI> Specify base URI to resolve relative URI in metalink:url and metalink:metaurl element in a metalink file stored in local disk. If URI points to a directory, URI must end with /.
-M, --metalink-file=<METALINK_FILE> The file path to ".meta4" and ".metalink" file. Reads input from stdin when - is specified.  You are not required to use this option because you can specify ".metalink" files without --metalink-file.
--metalink-language=<LANGUAGE> The language of the file to download.
--metalink-location=<LOCATION>[,...] The location of the preferred server.  A comma-delimited list of locations is acceptable, for example, jp,us.
--metalink-os=<OS> The operating system of the file to download.
--metalink-version=<VERSION> The version of the file to download.
--metalink-preferred-protocol=<PROTO> Specify preferred protocol.  The possible values are http, https, ftp and none.  Specify none to disable this feature.  Default: none
--metalink-enable-unique-protocol [true|false] If true is given and several protocols are available for a mirror in a metalink file, aria2 uses one of them.  Use --metalink-preferred-protocol option to specify the preference of protocol.  Default: true
RPC Options --enable-rpc [true|false] Enable JSON-RPC/XML-RPC server.  It is strongly recommended to set secret authorization token using --rpc-secret option.  See also --rpc-listen-port option.  Default: false
--pause [true|false] Pause download after added. This option is effective only when --enable-rpc=true is given.  Default: false
--pause-metadata [true|false] Pause downloads created as a result of metadata download. There are 3 types of metadata downloads in aria2: (1) downloading .torrent file. (2) downloading torrent metadata using magnet link. (3) downloading metalink file.  These metadata downloads will generate downloads using their metadata. This option pauses these subsequent downloads. This option is effective only when --enable-rpc=true is given.  Default: false
--rpc-allow-origin-all [true|false] Add Access-Control-Allow-Origin header field with value * to the RPC response.  Default: false
--rpc-certificate=<FILE> Use the certificate in FILE for RPC server. The certificate must be either in PKCS12 (.p12, .pfx) or in PEM format.
When using PEM, you have to specify the private key via --rpc-private-key as well. Use --rpc-secure option to enable encryption.
NOTE: AppleTLS users should use the KeyChain Access utility to first generate a self-signed SSL-Server certificate, e.g. using the wizard, and get the SHA-1 fingerprint from the Information dialog corresponding to that new certificate.  To start aria2c with --rpc-secure use --rpc-certificate=<SHA-1>.  Alternatively PKCS12 files are also supported. PEM files, however, are not supported.
--rpc-listen-all [true|false] Listen incoming JSON-RPC/XML-RPC requests on all network interfaces. If false is given, listen only on local loopback interface.  Default: false
--rpc-listen-port=<PORT> Specify a port number for JSON-RPC/XML-RPC server to listen to. Possible Values: 1024 -65535 Default: 6800
--rpc-max-request-size=<SIZE> Set max size of JSON-RPC/XML-RPC request. If aria2 detects the request is more than SIZE bytes, it drops connection. Default: 2M
--rpc-passwd=<PASSWD> Set JSON-RPC/XML-RPC password.
WARNING: --rpc-passwd option will be deprecated in the future release. Migrate to --rpc-secret option as soon as possible.
--rpc-private-key=<FILE> Use the private key in FILE for RPC server.  The private key must be decrypted and in PEM format. Use --rpc-secure option to enable encryption. See also --rpc-certificate option.
--rpc-save-upload-metadata [true|false] Save the uploaded torrent or metalink meta data in the directory specified by --dir option. The file name consists of SHA-1 hash hex string of meta data plus extension. For torrent, the extension is '.torrent'. For metalink, it is '.meta4'.  If false is given to this option, the downloads added by aria2.addTorrent() or aria2.addMetalink() will not be saved by --save-session option. Default: true
--rpc-secret=<TOKEN> Set RPC secret authorization token. Read RPC authorization secret token to know how this option value is used.
--rpc-secure [true|false] RPC transport will be encrypted by SSL/TLS.  The RPC clients must use https scheme to access the server. For WebSocket client, use wss scheme. Use --rpc-certificate and --rpc-private-key options to specify the server certificate and private key.
--rpc-user=<USER> Set JSON-RPC/XML-RPC user.
WARNING: --rpc-user option will be deprecated in the future release. Migrate to --rpc-secret option as soon as possible.
Advanced Options --allow-overwrite [true|false] Restart download from scratch if the corresponding control file doesn't exist.  See also --auto-file-renaming option.  Default: false
--allow-piece-length-change [true|false] If false is given, aria2 aborts download when a piece length is different from one in a control file.  If true is given, you can proceed but some download progress will be lost.  Default: false
--always-resume [true|false] Always resume download. If true is given, aria2 always tries to resume download and if resume is not possible, aborts download. If false is given, when all given URIs do not support resume or aria2 encounters N URIs which does not support resume (N is the value specified using --max-resume-failure-tries option), aria2 downloads file from scratch.  See --max-resume-failure-tries option. Default: true
--async-dns [true|false] Enable asynchronous DNS.  Default: true
--async-dns-server=<IPADDRESS>[,...] Comma separated list of DNS server address used in asynchronous DNS resolver. Usually asynchronous DNS resolver reads DNS server addresses from /etc/resolv.conf. When this option is used, it uses DNS servers specified in this option instead of ones in /etc/resolv.conf. You can specify both IPv4 and IPv6 address. This option is useful when the system does not have /etc/resolv.conf and user does not have the permission to create it.
--auto-file-renaming [true|false] Rename file name if the same file already exists.  This option works only in HTTP(S)/FTP download.  The new file name has a dot and a number(1..9999) appended after the name, but before the file extension, if any.  Default: true
--auto-save-interval=<SEC> Save a control file(*.aria2) every SEC seconds.  If 0 is given, a control file is not saved during download. aria2 saves a control file when it stops regardless of the value.  The possible values are between 0 to 600.  Default: 60
--conditional-get [true|false] Download file only when the local file is older than remote file. This function only works with HTTP(S) downloads only.  It does not work if file size is specified in Metalink. It also ignores Content-Disposition header.  If a control file exists, this option will be ignored.  This function uses If-Modified-Since header to get only newer file conditionally. When getting modification time of local file, it uses user supplied file name (see --out option) or file name part in URI if --out is not specified.  To overwrite existing file, --allow-overwrite is required.  Default: false
--conf-path=<PATH> Change the configuration file path to PATH.  Default: $HOME/.aria2/aria2.conf if present, otherwise $XDG_CONFIG_HOME/aria2/aria2.conf.
--console-log-level=<LEVEL> Set log level to output to console.  LEVEL is either debug, info, notice, warn or error.  Default: notice
--content-disposition-default-utf8 [true|false] Handle quoted string in Content-Disposition header as UTF-8 instead of ISO-8859-1, for example, the filename parameter, but not the extended version filename*.  Default: false
-D, --daemon [true|false] Run as daemon. The current working directory will be changed to / and standard input, standard output and standard error will be redirected to /dev/null. Default: false
--deferred-input [true|false] If true is given, aria2 does not read all URIs and options from file specified by --input-file option at startup, but it reads one by one when it needs later. This may reduce memory usage if input file contains a lot of URIs to download.  If false is given, aria2 reads all URIs and options at startup.  Default: false
WARNING: --deferred-input option will be disabled when --save-session is used together.
--disable-ipv6 [true|false] Disable IPv6. This is useful if you have to use broken DNS and want to avoid terribly slow AAAA record lookup. Default: false
--disk-cache=<SIZE> Enable disk cache. If SIZE is 0, the disk cache is disabled. This feature caches the downloaded data in memory, which grows to at most SIZE bytes. The cache storage is created for aria2 instance and shared by all downloads. The one advantage of the disk cache is reduce the disk I/O because the data are written in larger unit and it is reordered by the offset of the file.  If hash checking is involved and the data are cached in memory, we don't need to read them from the disk.  SIZE can include K or M (1K = 1024, 1M = 1024K). Default: 16M
--download-result=<OPT> This option changes the way Download Results is formatted. If OPT is default, print GID, status, average download speed and path/URI. If multiple files are involved, path/URI of first requested file is printed and remaining ones are omitted.  If OPT is full, print GID, status, average download speed, percentage of progress and path/URI. The percentage of progress and path/URI are printed for each requested file in each row.  If OPT is hide, Download Results is hidden.  Default: default
--dscp=<DSCP> Set DSCP value in outgoing IP packets of BitTorrent traffic for QoS. This parameter sets only DSCP bits in TOS field of IP packets, not the whole field. If you take values from /usr/include/netinet/ip.h divide them by 4 (otherwise values would be incorrect, e.g. your CS1 class would turn into CS4). If you take commonly used values from RFC, network vendors' documentation, Wikipedia or any other source, use them as they are.
--rlimit-nofile=<NUM> Set the soft limit of open file descriptors.  This open will only have effect when:
a. The system supports it (posix)
b. The limit does not exceed the hard limit.
c. The specified limit is larger than the current soft limit.
This is equivalent to setting nofile via ulimit, except that it will never decrease the limit.
This option is only available on systems supporting the rlimit API.
--enable-color [true|false] Enable color output for a terminal.  Default: true
--enable-mmap [true|false] Map files into memory. This option may not work if the file space is not pre-allocated. See --file-allocation.
Default: false
--event-poll=<POLL> Specify the method for polling events.  The possible values are epoll, kqueue, port, poll and select.  For each epoll, kqueue, port and poll, it is available if system supports it.  epoll is available on recent Linux. kqueue is available on various *BSD systems including Mac OS X. port is available on Open Solaris. The default value may vary depending on the system you use.
--file-allocation=<METHOD> Specify file allocation method.  none doesn't pre-allocate file space. prealloc pre-allocates file space before download begins. This may take some time depending on the size of the file.  If you are using newer file systems such as ext4 (with extents support), btrfs, xfs or NTFS(MinGW build only), falloc is your best choice. It allocates large(few GiB) files almost instantly. Don't use falloc with legacy file systems such as ext3 and FAT32 because it takes almost same time as prealloc and it blocks aria2 entirely until allocation finishes. falloc may not be available if your system doesn't have posix_fallocate(3) function.  trunc uses ftruncate(2) system call or platform-specific counterpart to truncate a file to a specified length.
Possible Values: none, prealloc, trunc, falloc Default: prealloc
WARNING: Using trunc seemingly allocates disk space very quickly, but what it actually does is that it sets file length metadata in file system, and does not allocate disk space at all.  This means that it does not help avoiding fragmentation.
NOTE: In multi file torrent downloads, the files adjacent forward to the specified files are also allocated if they share the same piece.
--force-save [true|false] Save download with --save-session option even if the download is completed or removed. This option also saves control file in that situations. This may be useful to save BitTorrent seeding which is recognized as completed state.  Default: false
--save-not-found [true|false] Save download with --save-session option even if the file was not found on the server. This option also saves control file in that situations.  Default: true
--gid=<GID> Set GID manually. aria2 identifies each download by the ID called GID. The GID must be hex string of 16 characters, thus [0-9a-fA-F] are allowed and leading zeros must not be stripped. The GID all 0 is reserved and must not be used. The GID must be unique, otherwise error is reported and the download is not added.  This option is useful when restoring the sessions saved using --save-session option. If this option is not used, new GID is generated by aria2.
--hash-check-only [true|false] If true is given, after hash check using --check-integrity option, abort download whether or not download is complete.  Default: false
--human-readable [true|false] Print sizes and speed in human readable format (e.g., 1.2Ki, 3.4Mi) in the console readout. Default: true
--interface=<INTERFACE> Bind sockets to given interface. You can specify interface name, IP address and host name.  Possible Values: interface, IP address, host name
NOTE: If an interface has multiple addresses, it is highly recommended to specify IP address explicitly. See also --disable-ipv6.  If your system doesn't have getifaddrs(3), this option doesn't accept interface name.
--keep-unfinished-download-result [true|false] Keep unfinished download results even if doing so exceeds --max-download-result.  This is useful if all unfinished downloads must be saved in session file (see --save-session option).  Please keep in mind that there is no upper bound to the number of unfinished download result to keep.  If that is undesirable, turn this option off.  Default: true
--max-download-result=<NUM> Set maximum number of download result kept in memory. The download results are completed/error/removed downloads. The download results are stored in FIFO queue and it can store at most NUM download results. When queue is full and new download result is created, oldest download result is removed from the front of the queue and new one is pushed to the back. Setting big number in this option may result high memory consumption after thousands of downloads. Specifying 0 means no download result is kept.  Note that unfinished downloads are kept in memory regardless of this option value. See --keep-unfinished-download-result option. Default: 1000
--max-mmap-limit=<SIZE> Set the maximum file size to enable mmap (see --enable-mmap option). The file size is determined by the sum of all files contained in one download. For example, if a download contains 5 files, then file size is the total size of those files. If file size is strictly greater than the size specified in this option, mmap will be disabled.  Default: 9223372036854775807
--max-resume-failure-tries=<N> When used with --always-resume=false, aria2 downloads file from scratch when aria2 detects N number of URIs that does not support resume. If N is 0, aria2 downloads file from scratch when all given URIs do not support resume.  See --always-resume option. Default: 0
--min-tls-version=<VERSION> Specify minimum SSL/TLS version to enable.  Possible Values: TLSv1.1, TLSv1.2, TLSv1.3 Default: TLSv1.2
--multiple-interface=<INTERFACES> Comma separated list of interfaces to bind sockets to. Requests will be splited among the interfaces to achieve link aggregation. You can specify interface name, IP address and hostname. If --interface is used, this option will be ignored.  Possible Values: interface, IP address, hostname
--log-level=<LEVEL> Set log level to output.  LEVEL is either debug, info, notice, warn or error.  Default: debug
--on-bt-download-complete=<COMMAND> For BitTorrent, a command specified in --on-download-complete is called after download completed and seeding is over. On the other hand, this option set the command to be executed after download completed but before seeding.  See Event Hook for more details about COMMAND.  Possible Values: /path/to/command
--on-download-complete=<COMMAND> Set the command to be executed after download completed.  See Event Hook for more details about COMMAND.  See also --on-download-stop option.  Possible Values: /path/to/command
--on-download-error=<COMMAND> Set the command to be executed after download aborted due to error.  See Event Hook for more details about COMMAND.  See also --on-download-stop option.  Possible Values: /path/to/command
--on-download-pause=<COMMAND> Set the command to be executed after download was paused.  See Event Hook for more details about COMMAND.  Possible Values: /path/to/command
--on-download-start=<COMMAND> Set the command to be executed after download got started.  See Event Hook for more details about COMMAND.  Possible Values: /path/to/command
--on-download-stop=<COMMAND> Set the command to be executed after download stopped. You can override the command to be executed for particular download result using --on-download-complete and --on-download-error. If they are specified, command specified in this option is not executed.  See Event Hook for more details about COMMAND.  Possible Values: /path/to/command
--optimize-concurrent-downloads [true|false|<A>:<B>] Optimizes the number of concurrent downloads according to the bandwidth available. aria2 uses the download speed observed in the previous downloads to adapt the number of downloads launched in parallel according to the rule N = A + B Log10(speed in Mbps). The coefficients A and B can be customized in the option arguments with A and B separated by a colon. The default values (A=5, B=25) lead to using typically 5 parallel downloads on 1Mbps networks and above 50 on 100Mbps networks. The number of parallel downloads remains constrained under the maximum defined by the --max-concurrent-downloads parameter.  Default: false
--piece-length=<LENGTH> Set a piece length for HTTP/FTP downloads. This is the boundary when aria2 splits a file. All splits occur at multiple of this length. This option will be ignored in BitTorrent downloads.  It will be also ignored if Metalink file contains piece hashes. Default: 1M
NOTE: The possible use case of --piece-length option is change the request range in one HTTP pipelined request.  To enable HTTP pipelining use --enable-http-pipelining.
--show-console-readout [true|false] Show console readout. Default: true
--stderr [true|false] Redirect all console output that would be otherwise printed in stdout to stderr.  Default: false
--summary-interval=<SEC> Set interval in seconds to output download progress summary. Setting 0 suppresses the output.  Default: 60
-Z, --force-sequential [true|false] Fetch URIs in the command-line sequentially and download each URI in a separate session, like the usual command-line download utilities.  Default: false
--max-overall-download-limit=<SPEED> Set max overall download speed in bytes/sec.  0 means unrestricted.  You can append K or M (1K = 1024, 1M = 1024K).  To limit the download speed per download, use --max-download-limit option.  Default: 0
--max-download-limit=<SPEED> Set max download speed per each download in bytes/sec. 0 means unrestricted.  You can append K or M (1K = 1024, 1M = 1024K).  To limit the overall download speed, use --max-overall-download-limit option.  Default: 0
--no-conf [true|false] Disable loading aria2.conf file.
--no-file-allocation-limit=<SIZE> No file allocation is made for files whose size is smaller than SIZE.  You can append K or M (1K = 1024, 1M = 1024K).  Default: 5M
-P, --parameterized-uri [true|false] Enable parameterized URI support.  You can specify set of parts: http://{sv1,sv2,sv3}/foo.iso.  Also you can specify numeric sequences with step counter: http://host/image[000-100:2].img.  A step counter can be omitted.  If all URIs do not point to the same file, such as the second example above, -Z option is required. Default: false
-q, --quiet [true|false] Make aria2 quiet (no console output).  Default: false
--realtime-chunk-checksum [true|false] Validate chunk of data by calculating checksum while downloading a file if chunk checksums are provided.  Default: true
--remove-control-file [true|false] Remove control file before download. Using with --allow-overwrite=true, download always starts from scratch. This will be useful for users behind proxy server which disables resume.
--save-session=<FILE> Save error/unfinished downloads to FILE on exit.  You can pass this output file to aria2c with --input-file option on restart. If you like the output to be gzipped append a .gz extension to the file name.  Please note that downloads added by aria2.addTorrent() and aria2.addMetalink() RPC method and whose meta data could not be saved as a file are not saved.  Downloads removed using aria2.remove() and aria2.forceRemove() will not be saved. GID is also saved with gid, but there are some restrictions, see below.
NOTE: Normally, GID of the download itself is saved. But some downloads use meta data (e.g., BitTorrent and Metalink). In this case, there are some restrictions.
magnet URI, and followed by torrent download GID of BitTorrent meta data download is saved.
URI to torrent file, and followed by torrent download GID of torrent file download is saved.
URI to metalink file, and followed by file downloads described in metalink file GID of metalink file download is saved.
local torrent file GID of torrent download is saved.
local metalink file Any meaningful GID is not saved.
--save-session-interval=<SEC> Save error/unfinished downloads to a file specified by --save-session option every SEC seconds. If 0 is given, file will be saved only when aria2 exits. Default: 0
--socket-recv-buffer-size=<SIZE> Set the maximum socket receive buffer in bytes.  Specifying 0 will disable this option. This value will be set to socket file descriptor using SO_RCVBUF socket option with setsockopt() call. Default: 0
--stop=<SEC> Stop application after SEC seconds has passed.  If 0 is given, this feature is disabled.  Default: 0
--stop-with-process=<PID> Stop application when process PID is not running.  This is useful if aria2 process is forked from a parent process. The parent process can fork aria2 with its own pid and when parent process exits for some reason, aria2 can detect it and shutdown itself.
--truncate-console-readout [true|false] Truncate console readout to fit in a single line.  Default: true
-v, --version Print the version number, copyright and the configuration information and exit.
Notes for Options Optional arguments The options that have its argument surrounded by square brackets([]) take an optional argument. Usually omitting the argument is evaluated to true. If you use short form of these options(such as -V) and give an argument, then the option name and its argument should be concatenated(e.g. -Vfalse). If any spaces are inserted between the option name and the argument, the argument will be treated as URI and usually this is not what you expect.
Units (K and M) Some options takes K and M to conveniently represent 1024 and 1048576 respectively.  aria2 detects these characters in case-insensitive way. In other words, k and m can be used as well as K and M respectively.
URI, MAGNET, TORRENT_FILE, METALINK_FILE You can specify multiple URIs in command-line.  Unless you specify --force-sequential option, all URIs must point to the same file or downloading will fail.
You can specify arbitrary number of BitTorrent Magnet URI. Please note that they are always treated as a separate download.  Both hex encoded 40 characters Info Hash and Base32 encoded 32 characters Info Hash are supported. The multiple tr parameters are supported.  Because BitTorrent Magnet URI is likely to contain & character, it is highly recommended to always quote URI with single(') or double(") quotation.  It is strongly recommended to enable DHT especially when tr parameter is missing. See http://www.bittorrent.org/beps/bep_0009.html for more details about BitTorrent Magnet URI.
You can also specify arbitrary number of torrent files and Metalink documents stored on a local drive. Please note that they are always treated as a separate download. Both Metalink4 and Metalink version 3.0 are supported.
You can specify both torrent file with -T option and URIs. By doing this, you can download a file from both torrent swarm and HTTP(S)/FTP/SFTP server at the same time, while the data from HTTP(S)/FTP/SFTP are uploaded to the torrent swarm.  For single file torrents, URI can be a complete URI pointing to the resource or if URI ends with /, name in torrent file in torrent is added. For multi-file torrents, name and path are added to form a URI for each file.
NOTE: Make sure that URI is quoted with single(') or double(") quotation if it contains & or any characters that have special meaning in shell.
Resuming Download Usually, you can resume transfer by just issuing same command (aria2c URI) if the previous transfer is made by aria2.
If the previous transfer is made by a browser or wget like sequential download manager, then use --continue option to continue the transfer.
Event Hook aria2 provides options to specify arbitrary command after specific event occurred. Currently following options are available: --on-bt-download-complete, --on-download-pause, --on-download-complete. --on-download-start, --on-download-error, --on-download-stop.
aria2 passes 3 arguments to specified command when it is executed.  These arguments are: GID, the number of files and file path.  For HTTP, FTP, and SFTP downloads, usually the number of files is 1.  BitTorrent download can contain multiple files.  If number of files is more than one, file path is first one.  In other words, this is the value of path key of first struct whose selected key is true in the response of aria2.getFiles() RPC method.  If you want to get all file paths, consider to use JSON-RPC/XML-RPC.  Please note that file path may change during download in HTTP because of redirection or Content-Disposition header.
Let's see an example of how arguments are passed to command:
$ cat hook.sh #!/bin/sh echo "Called with [$1] [$2] [$3]" $ aria2c --on-download-complete hook.sh http://example.org/file.iso Called with [1] [1] [/path/to/file.iso]
Because aria2 can handle multiple downloads at once, it encounters lots of errors in a session.  aria2 returns the following exit status based on the last error encountered.
0      If all downloads were successful.
1      If an unknown error occurred.
2      If time out occurred.
3      If a resource was not found.
4      If aria2 saw the specified number of "resource not found" error. See --max-file-not-found option.
5      If a download aborted because download speed was too slow.  See --lowest-speed-limit option.
6      If network problem occurred.
7      If there were unfinished downloads. This error is only reported if all finished downloads were successful and there were unfinished downloads in a queue when aria2 exited by pressing Ctrl-C by an user or sending TERM or INT signal.
8      If remote server did not support resume when resume was required to complete download.
9      If there was not enough disk space available.
10     If piece length was different from one in .aria2 control file. See --allow-piece-length-change option.
11     If aria2 was downloading same file at that moment.
12     If aria2 was downloading same info hash torrent at that moment.
13     If file already existed. See --allow-overwrite option.
14     If renaming file failed. See --auto-file-renaming option.
15     If aria2 could not open existing file.
16     If aria2 could not create new file or truncate existing file.
17     If file I/O error occurred.
18     If aria2 could not create directory.
19     If name resolution failed.
20     If aria2 could not parse Metalink document.
21     If FTP command failed.
22     If HTTP response header was bad or unexpected.
23     If too many redirects  occurred.
24     If HTTP authorization failed.
25     If aria2 could not parse bencoded file (usually ".torrent" file).
26     If ".torrent" file was corrupted or missing information that aria2 needed.
27     If Magnet URI was bad.
28     If bad/unrecognized option was given or unexpected option argument was given.
29     If the remote server was unable to handle the request due to a temporary overloading or maintenance.
30     If aria2 could not parse JSON-RPC request.
31     Reserved.  Not used.
32     If checksum validation failed.
NOTE: An error occurred in a finished download will not be reported as exit status.
aria2 recognizes the following environment variables.
http_proxy [http://][USER:PASSWORD@]HOST[:PORT] Specify proxy server for use in HTTP.  Overrides http-proxy value in configuration file.  The command-line option --http-proxy overrides this value.
https_proxy [http://][USER:PASSWORD@]HOST[:PORT] Specify proxy server for use in HTTPS.  Overrides https-proxy value in configuration file.  The command-line option --https-proxy overrides this value.
ftp_proxy [http://][USER:PASSWORD@]HOST[:PORT] Specify proxy server for use in FTP.  Overrides ftp-proxy value in configuration file.  The command-line option --ftp-proxy overrides this value.
all_proxy [http://][USER:PASSWORD@]HOST[:PORT] Specify proxy server for use if no protocol-specific proxy is specified.  Overrides all-proxy value in configuration file.  The command-line option --all-proxy overrides this value.
NOTE: Although aria2 accepts ftp:// and https:// scheme in proxy URI, it simply assumes that http:// is specified and does not change its behavior based on the specified scheme.
no_proxy [DOMAIN,...] Specify a comma-separated list of host names, domains and network addresses with or without a subnet mask where no proxy should be used.  Overrides the no-proxy value in configuration file.  The command-line option --no-proxy overrides this value.
aria2.conf By default, aria2 checks whether the legacy path $HOME/.aria2/aria2.conf is present, otherwise it parses $XDG_CONFIG_HOME/aria2/aria2.conf as its configuration file.  You can specify the path to configuration file using --conf-path option.  If you don't want to use the configuration file, use --no-conf option.
The configuration file is a text file and has 1 option per each line. In each line, you can specify name-value pair in the format: NAME=VALUE, where name is the long command-line option name without -- prefix. You can use same syntax for the command-line option. The lines beginning # are treated as comments:
# sample configuration file for aria2c listen-port=60000 dht-listen-port=60000 seed-ratio=1.0 max-upload-limit=50K ftp-pasv=true
NOTE: The confidential information such as user/password might be included in the configuration file. It is recommended to change file mode bits of the configuration file (e.g., chmod 600 aria2.conf), so that other user cannot see the contents of the file.
The environment variables, such as ${HOME}, are expanded by shell.  This means that those variables used in configuration file are not expanded. However, it is useful to ${HOME} to refer user's home directory in configuration file to specify file paths.  Therefore, aria2 expands ${HOME} found in the following option values to user's home directory:
• ca-certificate
• certificate
• dht-file-path
• dht-file-path6
• dir
• input-file
• load-cookies
• log
• metalink-file
• netrc-path
• on-bt-download-complete
• on-download-complete
• on-download-error
• on-download-start
• on-download-stop
• on-download-pause
• out
• private-key
• rpc-certificate
• rpc-private-key
• save-cookies
• save-session
• server-stat-if
• server-stat-of
• torrent-file
Note that this expansion occurs even if the above options are used in the command-line.  This means that expansion may occur 2 times: first, shell and then aria2c.
dht.dat Unless the legacy file paths $HOME/.aria2/dht.dat and $HOME/.aria2/dht6.dat are pointing to existing files, the routing table of IPv4 DHT is saved to the path $XDG_CACHE_HOME/aria2/dht.dat and the routing table of IPv6 DHT is saved to the path $XDG_CACHE_HOME/aria2/dht6.dat.
Netrc Netrc support is enabled by default for HTTP(S)/FTP/SFTP.  To disable netrc support, specify --no-netrc option.  Your .netrc file should have correct permissions(600).
If machine name starts ., aria2 performs domain-match instead of exact match. This is an extension of aria2. For example of domain match, imagine the following .netrc entry:
machine .example.org login myid password mypasswd
aria2.example.org domain-matches .example.org and uses myid and mypasswd.
Some domain-match example follow: example.net does not domain-match .example.org. example.org does not domain-match .example.org because of preceding .. If you want to match example.org, specify example.org.
Control File aria2 uses a control file to track the progress of a download.  A control file is placed in the same directory as the downloading file and its file name is the file name of downloading file with .aria2 appended.  For example, if you are downloading file.zip, then the control file should be file.zip.aria2.  (There is a exception for this naming convention.  If you are downloading a multi torrent, its control file is the "top directory" name of the torrent with .aria2 appended.  The "top directory" name is a value of "name" key in "info" directory in a torrent file.)
Usually a control file is deleted once download completed.  If aria2 decides that download cannot be resumed(for example, when downloading a file from a HTTP server which doesn't support resume), a control file is not created.
Normally if you lose a control file, you cannot resume download.  But if you have a torrent or metalink with chunk checksums for the file, you can resume the download without a control file by giving -V option to aria2c in command-line.
Input File The input file can contain a list of URIs for aria2 to download.  You can specify multiple URIs for a single entity: separate URIs on a single line using the TAB character.
Each line is treated as if it is provided in command-line argument. Therefore they are affected by --force-sequential and --parameterized-uri options.
Since URIs in the input file are directly read by aria2, they must not be quoted with single(') or double(") quotation.
Lines starting with # are treated as comments and skipped.
Additionally, the following options can be specified after each line of URIs. These optional lines must start with white space(s).
• all-proxy
• all-proxy-passwd
• all-proxy-user
• allow-overwrite
• allow-piece-length-change
• always-resume
• async-dns
• auto-file-renaming
• bt-enable-hook-after-hash-check
• bt-enable-lpd
• bt-exclude-tracker
• bt-external-ip
• bt-force-encryption
• bt-hash-check-seed
• bt-load-saved-metadata
• bt-max-peers
• bt-metadata-only
• bt-min-crypto-level
• bt-prioritize-piece
• bt-remove-unselected-file
• bt-request-peer-speed-limit
• bt-require-crypto
• bt-save-metadata
• bt-seed-unverified
• bt-stop-timeout
• bt-tracker
• bt-tracker-connect-timeout
• bt-tracker-interval
• bt-tracker-timeout
• check-integrity
• checksum
• conditional-get
• connect-timeout
• content-disposition-default-utf8
• continue
• dry-run
• enable-http-keep-alive
• enable-http-pipelining
• enable-mmap
• enable-peer-exchange
• file-allocation
• follow-metalink
• follow-torrent
• force-save
• ftp-passwd
• ftp-pasv
• ftp-proxy
• ftp-proxy-passwd
• ftp-proxy-user
• ftp-reuse-connection
• ftp-type
• ftp-user
• hash-check-only
• header
• http-accept-gzip
• http-auth-challenge
• http-no-cache
• http-passwd
• http-proxy
• http-proxy-passwd
• http-proxy-user
• http-user
• https-proxy
• https-proxy-passwd
• https-proxy-user
• index-out
• lowest-speed-limit
• max-connection-per-server
• max-download-limit
• max-file-not-found
• max-mmap-limit
• max-resume-failure-tries
• max-tries
• max-upload-limit
• metalink-base-uri
• metalink-enable-unique-protocol
• metalink-language
• metalink-location
• metalink-os
• metalink-preferred-protocol
• metalink-version
• min-split-size
• no-file-allocation-limit
• no-netrc
• no-proxy
• parameterized-uri
• pause-metadata
• piece-length
• proxy-method
• realtime-chunk-checksum
• referer
• remote-time
• remove-control-file
• retry-wait
• reuse-uri
• rpc-save-upload-metadata
• seed-ratio
• seed-time
• select-file
• split
• ssh-host-key-md
• stream-piece-selector
• timeout
• uri-selector
• use-head
• user-agent
These options have exactly same meaning of the ones in the command-line options, but it just applies to the URIs it belongs to.  Please note that for options in input file -- prefix must be stripped.
For example, the content of uri.txt is:
http://server/file.iso http://mirror/file.iso dir=/iso_images out=file.img http://foo/bar
If aria2 is executed with -i uri.txt -d /tmp options, then file.iso is saved as /iso_images/file.img and it is downloaded from http://server/file.iso and http://mirror/file.iso.  The file bar is downloaded from http://foo/bar and saved as /tmp/bar.
In some cases, out parameter has no effect.  See note of --out option for the restrictions.
Server Performance Profile This section describes the format of server performance profile.  The file is plain text and each line has several NAME=VALUE pair, delimited by comma.  Currently following NAMEs are recognized:
host   Host name of the server. Required.
protocol Protocol for this profile, such as ftp, http. Required.
dl_speed The average download speed observed in the previous download in bytes per sec.  Required.
sc_avg_speed The average download speed observed in the previous download in bytes per sec. This value is only updated if the download is done in single connection environment and only used by AdaptiveURISelector. Optional.
mc_avg_speed The average download speed observed in the previous download in bytes per sec. This value is only updated if the download is done in multi connection environment and only used by AdaptiveURISelector. Optional.
counter How many times the server is used. Currently this value is only used by AdaptiveURISelector.  Optional.
last_updated Last contact time in GMT with this server, specified in the seconds since the Epoch(00:00:00 on January 1, 1970, UTC). Required.
status ERROR is set when server cannot be reached or out-of-service or timeout occurred. Otherwise, OK is set.
Those fields must exist in one line. The order of the fields is not significant. You can put pairs other than the above; they are simply ignored.
An example follows:
host=localhost, protocol=http, dl_speed=32000, last_updated=1222491640, status=OK host=localhost, protocol=ftp, dl_speed=0, last_updated=1222491632, status=ERROR
aria2 provides JSON-RPC over HTTP and XML-RPC over HTTP interfaces that offer basically the same functionality.  aria2 also provides JSON-RPC over WebSocket. JSON-RPC over WebSocket uses the same method signatures and response format as JSON-RPC over HTTP, but additionally provides server-initiated notifications. See JSON-RPC over WebSocket section for more information.
The request path of the JSON-RPC interface (for both over HTTP and over WebSocket) is /jsonrpc.  The request path of the XML-RPC interface is /rpc.
The WebSocket URI for JSON-RPC over WebSocket is ws://HOST:PORT/jsonrpc. If you enabled SSL/TLS encryption, use wss://HOST:PORT/jsonrpc instead.
The implemented JSON-RPC is based on JSON-RPC 2.0 <‐ http://jsonrpc.org/specification>, and supports HTTP POST and GET (JSONP).  The WebSocket transport is an aria2 extension.
The JSON-RPC interface does not support notifications over HTTP, but the RPC server will send notifications over WebSocket. It also does not support floating point numbers. The character encoding must be UTF-8.
When reading the following documentation for JSON-RPC, interpret structs as JSON objects.
Terminology GID The GID (or gid) is a key to manage each download. Each download will be assigned a unique GID. The GID is stored as 64-bit binary value in aria2.  For RPC access, it is represented as a hex string of 16 characters (e.g., 2089b05ecca3d829). Normally, aria2 generates this GID for each download, but the user can specify GIDs manually using the --gid option. When querying downloads by GID, you can specify only the prefix of a GID as long as it is unique among others.
RPC authorization secret token As of 1.18.4, in addition to HTTP basic authorization, aria2 provides RPC method-level authorization. In a future release, HTTP basic authorization will be removed and RPC method-level authorization will become mandatory.
To use RPC method-level authorization, the user has to specify an RPC secret authorization token using the --rpc-secret option. For each RPC method call, the caller has to include the token prefixed with token:. Even when the --rpc-secret option is not used, if the first parameter in the RPC method is a string and starts with token:, it will removed from the parameter list before the request is being processed.
For example, if the RPC secret authorization token is $$secret$$, calling aria2.addUri RPC method would have to look like this:
aria2.addUri("token:$$secret$$", ["http://example.org/file"])
The system.multicall RPC method is treated specially. Since the XML-RPC specification only allows a single array as a parameter for this method, we don't specify the token in the call. Instead, each nested method call has to provide the token as the first parameter as described above.
NOTE: The secret token validation in aria2 is designed to take at least a certain amount of time to mitigate brute-force/dictionary attacks against the RPC interface. Therefore it is recommended to prefer Batch or system.multicall requests when appropriate.
system.listMethods and system.listNotifications can be executed without token. Since they just return available methods/notifications, they do not alter anything, they're safe without secret token.
Methods All code examples are compatible with the Python 2.7 interpreter.  For information on the secret parameter, see RPC authorization secret token.
aria2.addUri([secret], uris[, options[, position]]) This method adds a new download. uris is an array of HTTP/FTP/SFTP/BitTorrent URIs (strings) pointing to the same resource.  If you mix URIs pointing to different resources, then the download may fail or be corrupted without aria2 complaining. When adding BitTorrent Magnet URIs, uris must have only one element and it should be BitTorrent Magnet URI.  options is a struct and its members are pairs of option name and value.  See Options below for more details.  If position is given, it must be an integer starting from 0. The new download will be inserted at position in the waiting queue. If position is omitted or position is larger than the current size of the queue, the new download is appended to the end of the queue.  This method returns the GID of the newly registered download.
JSON-RPC Example
The following example adds http://example.org/file:
>>> import urllib2, json >>> jsonreq = json.dumps({'jsonrpc':'2.0', 'id':'qwer', ...                       'method':'aria2.addUri', ...                       'params':[['http://example.org/file']]}) >>> c = urllib2.urlopen('http://localhost:6800/jsonrpc', jsonreq) >>> c.read() '{"id":"qwer","jsonrpc":"2.0","result":"2089b05ecca3d829"}'
XML-RPC Example
>>> import xmlrpclib >>> s = xmlrpclib.ServerProxy('http://localhost:6800/rpc') >>> s.aria2.addUri(['http://example.org/file']) '2089b05ecca3d829'
The following example adds a new download with two sources and some options:
>>> s.aria2.addUri(['http://example.org/file', 'http://mirror/file'], dict(dir="/tmp")) 'd2703803b52216d1'
The following example adds a download and inserts it to the front of the queue:
>>> s.aria2.addUri(['http://example.org/file'], {}, 0) 'ca3d829cee549a4d'