How to check for existence of an URL?

[mamo]

Dear Eviewers,

I use Eviews 10+.
Would anybody have a suggestion how to check for the existence of an url?
(for instance: excel file with US GDP data at the BEA, "https://www.bea.gov/national/xls/gdplev.xlsx")
It seems that the Eviews-function "@fileexist" does not work with urls.

Best, mamo

[EViews Gareth]

Try opening it and if it fails, it doesn’t exist?

[mamo]

Well I am looking for sth which can be applied in a program, for instance

%url="https://www.bea.gov/national/xls/gdplev.xlsx"
if @urlexist(%url) then
'do something
else
'do something else
endif

[EViews Gareth]

Code: Select all

setmaxerrs 2 wfopen "https://www.bea.gov/national/xls/gdplev.xlsx" if @errorcount>0 then 'do something else ' do something else endif

[mamo]

Many thanks, this is a workable patch-around.
For completeness and for whom it may be useful, I provide below a subroutine with improved code (disabling also log-messages, and resetting the error counter).
However, this work-around requires reading in the respective file linked to by the url. If the file is large, this wastes considerable computing time.
Hence, I'd like to suggest to the EVIEWS team to consider implementing a more efficient approach in a function named like '@urlexist' in upcoming versions.

mamo

Code: Select all

' %url="http://www.euklems.net/TCB/2017/US_output_17i.xlsx" ' smaller file; routine works reasonably fast %url="https://www.bea.gov/national/xls/gdplev.xlsx" ' large file; routine take a lot of time for a simple check! !checkurl=0 call checkurl(%url, !checkurl) statusline !checkurl subroutine checkurl(string %url, scalar !check) setmaxerrs 2 logmode -e !check=0 wfopen %url if @errorcount=0 then !check=1 wfclose endif clearerrs setmaxerrs 1 logmode 2 endsub