Este fin de semana, iba a descargar las ROMs y CHDs actualizados para MAME. Llevaba sin actualizarlo unos 3 años, y ya tocaba. Los tiempos han cambiado, y ahora las descargas son mucho más sencillas gracias al esfuerzo del Internet Archive, pero siguen siendo enormes. Hablamos de 500 Gb. comprimidos en ZIP, 60 Gb. para las ROM, y 440 Gb. para los CHD, es decir, al menos 50 horas de transferencia ininterrumpida.

Desde los tiempos de Opera 12, que incluso soportaba descargas por Bittorrent, los navegadores se han simplificado tanto, que lo máximo que permiten, es parar la descarga, y volverla a continuar cuando nos interese. Pero solamente, mientras el navegador esté abierto, ya que si lo cerramos, se perderá todo el progreso. Esto ocurre en Chrome, y el resto de navegadores basados en Webkit como Opera o Vivaldi y otros.

Tampoco nos permiten limitar el ancho de banda que queremos utilizar de nuestra conexión, de manera que no se sature al ocuparla entera, y podamos trabajar normalmente mientras descargamos en segundo plano. Por supuesto, hay extensiones que permiten continuar nuestros downloads aunque cerremos el navegador, sin embargo, resulta extraño que sea una función que no venga de serie.

Probé también con Shareaza, y descubrí que no soportaba el protocolo HTTPS. También revisé algunos gestores de descargas portables, y me encontré con que la mayoría de ellos reservaban el espacio para el archivo completo al inicial la descarga. Aunque a priori puede parecer ventajoso, escribir el archivo completo al principio, porque ayuda a reducir la fragmentación, no suele tener sentido, ya que lo que descargamos, suelen ser archivos temporales que eliminaremos una vez descomprimidos o instalados, así que nos da igual que estén fragmentados. El inconveniente de reservar el espacio, es que tendremos al disco duro trabajando a tope durante más de una hora, y en ese tiempo, nuestro equipo será inusable, al estar ocupadas las transferencias con tanto trasiego.

Es decir, que necesitaba, lo que creo que la mayoría de usuarios necesitamos:
1) Poder parar las descargas, y continuarlas más adelante, incluso habiendo apagado el ordenador.
2) Poder limitar el ancho de banda que usarían los archivos para descargarse.
3) No escribir el archivo completo al principio.

Entonces me acordé de WGET, la clásica herramienta de UNIX y Linux, dedicada precisamente a las descargas. Lo más complicado, y no lo fue mucho, fue conseguirla, ya que por ejemplo el proyecto GNU for Windows, lleva años sin actualizar los binarios. Por fortuna, encontré a Jernej Simončič, que incluso ofrece ejecutables para Win64, y enlazados con las últimas versiones de OpenSSL. Como además, es una herramienta por linea de comandos, el consumo de recursos es mínimo.

Así que nada tan fácil, como ejecutar una orden parecida a esta:
wget –continue –limit-rate 1500k https://ia801508.us.archive.org/25/items/MAME_0.185_ROMs_merged/MAME_0.185_ROMs_merged.zip

Donde el modificador continue indica que queremos que las descargas se puedan reanudar (resume), y –limit-rate limita el ancho de banda usado a 1200 Kb. por segundo. Al final de este artículo, encontrarás de todas formas la referencia de wget completa.

GNU Wget 1.19.1, a non-interactive network retriever.
Usage: wget [OPTION]... [URL]...

Mandatory arguments to long options are mandatory for short options too.

Startup:
  -V,  --version                   display the version of Wget and exit
  -h,  --help                      print this help
  -b,  --background                go to background after startup
  -e,  --execute=COMMAND           execute a `.wgetrc'-style command

Logging and input file:
  -o,  --output-file=FILE          log messages to FILE
  -a,  --append-output=FILE        append messages to FILE
  -d,  --debug                     print lots of debugging information
  -q,  --quiet                     quiet (no output)
  -v,  --verbose                   be verbose (this is the default)
  -nv, --no-verbose                turn off verboseness, without being quiet
       --report-speed=TYPE         output bandwidth as TYPE.  TYPE can be bits
  -i,  --input-file=FILE           download URLs found in local or external FILE
       --input-metalink=FILE       download files covered in local Metalink FILE
  -F,  --force-html                treat input file as HTML
  -B,  --base=URL                  resolves HTML input-file links (-i -F)
                                     relative to URL
       --config=FILE               specify config file to use
       --no-config                 do not read any config file
       --rejected-log=FILE         log reasons for URL rejection to FILE

Download:
  -t,  --tries=NUMBER              set number of retries to NUMBER (0 unlimits)
       --retry-connrefused         retry even if connection is refused
  -O,  --output-document=FILE      write documents to FILE
  -nc, --no-clobber                skip downloads that would download to
                                     existing files (overwriting them)
  -c,  --continue                  resume getting a partially-downloaded file
       --start-pos=OFFSET          start downloading from zero-based position OFFSET
       --progress=TYPE             select progress gauge type
       --show-progress             display the progress bar in any verbosity mode
  -N,  --timestamping              don't re-retrieve files unless newer than
                                     local
       --no-if-modified-since      don't use conditional if-modified-since get
                                     requests in timestamping mode
       --no-use-server-timestamps  don't set the local file's timestamp by
                                     the one on the server
  -S,  --server-response           print server response
       --spider                    don't download anything
  -T,  --timeout=SECONDS           set all timeout values to SECONDS
       --dns-timeout=SECS          set the DNS lookup timeout to SECS
       --connect-timeout=SECS      set the connect timeout to SECS
       --read-timeout=SECS         set the read timeout to SECS
  -w,  --wait=SECONDS              wait SECONDS between retrievals
       --waitretry=SECONDS         wait 1..SECONDS between retries of a retrieval
       --random-wait               wait from 0.5*WAIT...1.5*WAIT secs between retrievals
       --no-proxy                  explicitly turn off proxy
  -Q,  --quota=NUMBER              set retrieval quota to NUMBER
       --bind-address=ADDRESS      bind to ADDRESS (hostname or IP) on local host
       --limit-rate=RATE           limit download rate to RATE
       --no-dns-cache              disable caching DNS lookups
       --restrict-file-names=OS    restrict chars in file names to ones OS allows
       --ignore-case               ignore case when matching files/directories
  -4,  --inet4-only                connect only to IPv4 addresses
  -6,  --inet6-only                connect only to IPv6 addresses
       --prefer-family=FAMILY      connect first to addresses of specified family,
                                     one of IPv6, IPv4, or none
       --user=USER                 set both ftp and http user to USER
       --password=PASS             set both ftp and http password to PASS
       --ask-password              prompt for passwords
       --use-askpass=COMMAND       specify credential handler for requesting 
                                     username and password.  If no COMMAND is 
                                     specified the WGET_ASKPASS or the SSH_ASKPASS 
                                     environment variable is used.
       --no-iri                    turn off IRI support
       --local-encoding=ENC        use ENC as the local encoding for IRIs
       --remote-encoding=ENC       use ENC as the default remote encoding
       --unlink                    remove file before clobber
       --keep-badhash              keep files with checksum mismatch (append .badhash)
       --metalink-index=NUMBER     Metalink application/metalink4+xml metaurl ordinal NUMBER
       --metalink-over-http        use Metalink metadata from HTTP response headers
       --preferred-location        preferred location for Metalink resources

Directories:
  -nd, --no-directories            don't create directories
  -x,  --force-directories         force creation of directories
  -nH, --no-host-directories       don't create host directories
       --protocol-directories      use protocol name in directories
  -P,  --directory-prefix=PREFIX   save files to PREFIX/..
       --cut-dirs=NUMBER           ignore NUMBER remote directory components

HTTP options:
       --http-user=USER            set http user to USER
       --http-password=PASS        set http password to PASS
       --no-cache                  disallow server-cached data
       --default-page=NAME         change the default page name (normally
                                     this is 'index.html'.)
  -E,  --adjust-extension          save HTML/CSS documents with proper extensions
       --ignore-length             ignore 'Content-Length' header field
       --header=STRING             insert STRING among the headers
       --max-redirect              maximum redirections allowed per page
       --proxy-user=USER           set USER as proxy username
       --proxy-password=PASS       set PASS as proxy password
       --referer=URL               include 'Referer: URL' header in HTTP request
       --save-headers              save the HTTP headers to file
  -U,  --user-agent=AGENT          identify as AGENT instead of Wget/VERSION
       --no-http-keep-alive        disable HTTP keep-alive (persistent connections)
       --no-cookies                don't use cookies
       --load-cookies=FILE         load cookies from FILE before session
       --save-cookies=FILE         save cookies to FILE after session
       --keep-session-cookies      load and save session (non-permanent) cookies
       --post-data=STRING          use the POST method; send STRING as the data
       --post-file=FILE            use the POST method; send contents of FILE
       --method=HTTPMethod         use method "HTTPMethod" in the request
       --body-data=STRING          send STRING as data. --method MUST be set
       --body-file=FILE            send contents of FILE. --method MUST be set
       --content-disposition       honor the Content-Disposition header when
                                     choosing local file names (EXPERIMENTAL)
       --content-on-error          output the received content on server errors
       --auth-no-challenge         send Basic HTTP authentication information
                                     without first waiting for the server's
                                     challenge

HTTPS (SSL/TLS) options:
       --secure-protocol=PR        choose secure protocol, one of auto, SSLv2,
                                     SSLv3, TLSv1 and PFS
       --https-only                only follow secure HTTPS links
       --no-check-certificate      don't validate the server's certificate
       --certificate=FILE          client certificate file
       --certificate-type=TYPE     client certificate type, PEM or DER
       --private-key=FILE          private key file
       --private-key-type=TYPE     private key type, PEM or DER
       --ca-certificate=FILE       file with the bundle of CAs
       --ca-directory=DIR          directory where hash list of CAs is stored
       --crl-file=FILE             file with bundle of CRLs
       --pinnedpubkey=FILE/HASHES  Public key (PEM/DER) file, or any number
                                   of base64 encoded sha256 hashes preceded by
                                   'sha256//' and separated by ';', to verify
                                   peer against
       --random-file=FILE          file with random data for seeding the SSL PRNG

HSTS options:
       --no-hsts                   disable HSTS
       --hsts-file                 path of HSTS database (will override default)

FTP options:
       --ftp-user=USER             set ftp user to USER
       --ftp-password=PASS         set ftp password to PASS
       --no-remove-listing         don't remove '.listing' files
       --no-glob                   turn off FTP file name globbing
       --no-passive-ftp            disable the "passive" transfer mode
       --preserve-permissions      preserve remote file permissions
       --retr-symlinks             when recursing, get linked-to files (not dir)

FTPS options:
       --ftps-implicit                 use implicit FTPS (default port is 990)
       --ftps-resume-ssl               resume the SSL/TLS session started in the control connection when
                                         opening a data connection
       --ftps-clear-data-connection    cipher the control channel only; all the data will be in plaintext
       --ftps-fallback-to-ftp          fall back to FTP if FTPS is not supported in the target server
WARC options:
       --warc-file=FILENAME        save request/response data to a .warc.gz file
       --warc-header=STRING        insert STRING into the warcinfo record
       --warc-max-size=NUMBER      set maximum size of WARC files to NUMBER
       --warc-cdx                  write CDX index files
       --warc-dedup=FILENAME       do not store records listed in this CDX file
       --no-warc-compression       do not compress WARC files with GZIP
       --no-warc-digests           do not calculate SHA1 digests
       --no-warc-keep-log          do not store the log file in a WARC record
       --warc-tempdir=DIRECTORY    location for temporary files created by the
                                     WARC writer

Recursive download:
  -r,  --recursive                 specify recursive download
  -l,  --level=NUMBER              maximum recursion depth (inf or 0 for infinite)
       --delete-after              delete files locally after downloading them
  -k,  --convert-links             make links in downloaded HTML or CSS point to
                                     local files
       --convert-file-only         convert the file part of the URLs only (usually known as the basename)
       --backups=N                 before writing file X, rotate up to N backup files
  -K,  --backup-converted          before converting file X, back up as X.orig
  -m,  --mirror                    shortcut for -N -r -l inf --no-remove-listing
  -p,  --page-requisites           get all images, etc. needed to display HTML page
       --strict-comments           turn on strict (SGML) handling of HTML comments

Recursive accept/reject:
  -A,  --accept=LIST               comma-separated list of accepted extensions
  -R,  --reject=LIST               comma-separated list of rejected extensions
       --accept-regex=REGEX        regex matching accepted URLs
       --reject-regex=REGEX        regex matching rejected URLs
       --regex-type=TYPE           regex type (posix)
  -D,  --domains=LIST              comma-separated list of accepted domains
       --exclude-domains=LIST      comma-separated list of rejected domains
       --follow-ftp                follow FTP links from HTML documents
       --follow-tags=LIST          comma-separated list of followed HTML tags
       --ignore-tags=LIST          comma-separated list of ignored HTML tags
  -H,  --span-hosts                go to foreign hosts when recursive
  -L,  --relative                  follow relative links only
  -I,  --include-directories=LIST  list of allowed directories
       --trust-server-names        use the name specified by the redirection
                                     URL's last component
  -X,  --exclude-directories=LIST  list of excluded directories
  -np, --no-parent                 don't ascend to the parent directory

Mail bug reports and suggestions to 

Actualizado a jueves 20 de julio de 2017. 8:19:
Actualizo con el importante aporte de EdSon, agregando la opción documentada de no comprobar certificados SSL, para evitar posibles errores en la descarga, pero también, la importante opción no documentada de omitir robots.txt:
wget -e robots=off –nocheck-certificate –continue –limit-rate 1500k https://ia801508.us.archive.org/25/items/MAME_0.185_ROMs_merged/MAME_0.185_ROMs_merged.zip