DownloadFile

NAME

SYNOPSIS

DownloadFile -s URL -d filename [ -r retries[,interval] ][ -b ]

DownloadFile -s URL -d filename [ -r retries[,interval] ] -l [ -t timeout | minimum-maximum ][ -z timezone ][ -n ][ -i ]

AVAILABILITY

DESCRIPTION

One time file download

DownloadFile -s URL -d filename [ -r retries[,interval] ][ -b ]

This is used to download the specified file once and terminate.

Repetitive file download

DownloadFile -s URL -d filename [ -r retries[,interval] ] -l [ -t timeout | minimum-maximum ][ -z timezone ][ -n ][ -i ]

When using the -l option (=loop download) the file addressed in the web URL is downloaded repetitively and saved to a local file with a time stamp added to the file name. The downloaded file is only kept if it is different to the previously downloaded file.

This mode can be used for instance to download a webcam image and keep all files to create a time lapse view of the downloaded image files.

The time stamp that is added to the file name has the format YYYYMMDDhhmmss. It might make sense that the time stamp is equal to the time where the web cam is located. To do so, set the time zone of the origin using the -z option or set the TZ=timezone environment variable.

The command shows a wait output indicating a countdown to the next download attempt. When pressing any key during this output the waiting is aborted and an immediate download attempt is performed.

OPTIONS

-h

usage message.

-V

print program version.

-s URL

source URL.

If - is specified as file name, the URL is read from stdin (standard input).

-d filename

destination file name.

-b

add a 'cachebreaker' (e.g.: http://acme.ch/webcam.jpg?1534528554) to the URL to force a fresh download of the file from the server independent of caching proxies in between.

-r retries

number of retries on failed file download.

-r retries,interval

number of retries on failed file download and interval between retries in seconds. The default number of retires is 0 and the minimum retry interval is 4 seconds.

-l

indefinitely repeat the download (=loop download) and save the downloaded file with a time stamp added to the file name. The downloading can be stopped pressing the Ctrl+C keys.

-t timeout

fix interval in seconds between downloads. Default is 60 seconds.

-t minimum-maximum

dynamic interval between a minimum and a maximum in seconds between downloads. The interval is dynamically adjusted between the minimum and the maximum interval.

-z timezone

Timezone of the time stamp in POSIX notification:

Take care in computing the sign of the time difference. Because the time difference is the offset from local time to UTC (rather than the reverse), its sign may be the opposite of what you might intuitively expect. For time zones ahead of UTC, the time difference is negative; for those behind UTC, the difference is positive [1].

Examples:

 -z UTC      England/London (Greenwich Mean Time)
 -z UTC+8    USA/Santa Barbara
 -z UTC+5    Peru/Lima
 -z UTC-1    Switzerland/Beringen
 -z UTC-2    Switzerland/Beringen (Daylight Saving Time)
 -z UTC-10   Australia/Sydney

See: https://www.timeanddate.com/time/map/ for a world map of time zones.

-n

start the looped download (-l) in non-interactive mode to wit the question "start download <yn>:" is automatically answered with y.

-i

create a shortcut on the Desktop with the selected -l options for later re-run of the command.

ENVIRONMENT

TZ=timezone

time zone as in the -z timezone command line option.

EXIT STATUS

0

no error.

1

download failed (when a single file was downloaded).

4

usage message displayed.

5

version printed.

FILES

EXAMPLES

SEE ALSO

NOTES

Therefore, if you are able to download a file using the Internet Explorer, the DownloadFile command is also able to download it.

Bibliography:

[1]

Alphabetical Function Reference, _tzset, 17.08.2018, Microsoft™, URL: https://msdn.microsoft.com/en-us/library/90s5c885.aspx

BUGS

AUTHOR

COPYRIGHT

This is free software; see WA2LSimpleBackup/man/COPYING for copying conditions. There is ABSOLUTELY NO WARRANTY; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.