[NTG-context] Files on a server

Taco Hoekwater taco at elvenkind.com
Wed May 16 14:23:42 CEST 2018


Or use luasocket, which is included in the luatex binary:

\startluacode
content, status, authinfo = socket.http.request{
    method = "HEAD",
    url = "http://hansvandermeer.myqnapcloud.com/archive/denhaag/hga-dtb-1869-6040.pdf” 
}

print (status)

\stopluacode

prints ‘404’ in this case.

Taco

> On 16 May 2018, at 13:45, Henri Menke <henrimenke at gmail.com> wrote:
> 
> On 05/16/2018 11:23 PM, Hans van der Meer wrote:
>> I would be satisfied when a returned 404 error code will be handled
>> within a reasonable (configurable) time delay. As for redirection, there
>> I would not mind if it is not included.
>> Restrictions like that are not a problem for me, because this is for
>> building a pdf that accesses many internet located files. The check on
>> existence is therefore especially meant for spotting missing or misnamed
>> files.
> 
> You can use libcurl via ffi: https://curl.haxx.se/libcurl/
> 
> \startluacode
> local ffi = require("ffi")
> 
> ffi.cdef[[
> typedef struct Curl_easy CURL;
> typedef int CURLcode;
> typedef int CURLoption;
> typedef int CURLINFO;
> typedef size_t(*callback)(void *buffer, size_t size, size_t nmemb, void
> *userp);
> 
> CURLcode curl_global_init(long flags);
> CURL *curl_easy_init(void);
> CURLcode curl_easy_setopt(CURL *curl, CURLoption option, ...);
> CURLcode curl_easy_perform(CURL *curl);
> CURLcode curl_easy_getinfo(CURL *curl, CURLINFO info, ...);
> void curl_easy_cleanup(CURL *curl);
> void curl_global_cleanup(void);
> ]]
> 
> -- magic numbers
> local CURL_GLOBAL_DEFAULT = 3
> local CURLOPT_URL = 10002
> local CURLOPT_NOBODY = 44
> local CURLOPT_HEADER = 42
> local CURLOPT_WRITEFUNCTION = 20011
> local CURLINFO_RESPONSE_CODE = 0x200000 + 2
> 
> local lcurl = ffi.load("curl")
> 
> local function discard(buffer, size, nmemb, userp)
>    return size * nmemb
> end
> 
> function check_status(url)
>    lcurl.curl_global_init(CURL_GLOBAL_DEFAULT)
> 
>    local curl = lcurl.curl_easy_init()
> 
>    lcurl.curl_easy_setopt(curl, CURLOPT_URL, url)
>    lcurl.curl_easy_setopt(curl, CURLOPT_NOBODY, ffi.cast("long",1))
>    lcurl.curl_easy_setopt(curl, CURLOPT_HEADER, ffi.cast("long",1))
>    lcurl.curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION,
> ffi.cast("callback",discard));
> 
>    local res = lcurl.curl_easy_perform(curl)
>    local c_http_code = ffi.new("long[1]")
>    lcurl.curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, c_http_code);
> 
>    lcurl.curl_easy_cleanup(curl)
>    lcurl.curl_global_cleanup()
> 
>    return tonumber(c_http_code[0])
> end
> \stopluacode
> 
> \starttext
> 
> \ctxlua{context(check_status("http://example.com/"))}
> 
> \ctxlua{context(check_status("https://example.com/"))}
> 
> \ctxlua{context(check_status("https://example.com/xyz"))}
> 
> \stoptext
> 
>> 
>> Hans van der Meer
>> 
>>> On 16 May 2018, at 12:41, Henri Menke <henrimenke at gmail.com
>>> <mailto:henrimenke at gmail.com>> wrote:
>>> 
>>> On 05/16/2018 09:31 PM, Hans van der Meer wrote:
>>>> I tried to determine the existence of a file on the internet. See the
>>>> following macro call:
>>>> 
>>>>         % Test if file exists.
>>>>         \edef\theurl{\linkprotocol://\urlbase\xmlatt{#1}{link}\thesuffix}
>>>>         \doiffileelse
>>>>         {\theurl}
>>>>         {\verbose{HVDM-PEV-TEST}{file exists: \theurl}}
>>>>         {\verbose{HVDM-PEV-TEST}{file does not exist: \theurl}}
>>>> 
>>>> It seems that \doiffileelse always results in true except for local
>>>> files where nonexistence is correctly handled.
>>>> 
>>>> For example the following url definitely does not exist but nevertheless
>>>> \doiffileelse reports its existence:
>>>> HVDM-PEV-TEST   > file exists:
>>>> http://hansvandermeer.myqnapcloud.com/archive/denhaag/hga-dtb-1869-6040.pdf
>>>> 
>>>> Is it possible that the \doiffile macros are extended for files on the
>>>> internet or a correponding set \doifurl is developed?
>>> 
>>> I'm not speaking for the devs here, but I don't think that this is going
>>> to be included.  It would require that all webpages send proper 404
>>> codes and timeout after reasonable delay.  Also how would you handle
>>> redirects?  Should the ConTeXt run be stalled because checking for a
>>> files existence on the web is caught in a redirect loop?
>>> 
>>>> 
>>>> Hans van der Meer
>>>> 
>>>> 
>>>> 
>>>> ___________________________________________________________________________________
>>>> If your question is of interest to others as well, please add an
>>>> entry to the Wiki!
>>>> 
>>>> maillist : ntg-context at ntg.nl <mailto:ntg-context at ntg.nl> /
>>>> http://www.ntg.nl/mailman/listinfo/ntg-context
>>>> webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
>>>> archive  : https://bitbucket.org/phg/context-mirror/commits/
>>>> wiki     : http://contextgarden.net
>>>> ___________________________________________________________________________________
>>>> 
>>> 
>>> ___________________________________________________________________________________
>>> If your question is of interest to others as well, please add an entry
>>> to the Wiki!
>>> 
>>> maillist : ntg-context at ntg.nl
>>> <mailto:ntg-context at ntg.nl> / http://www.ntg.nl/mailman/listinfo/ntg-context
>>> webpage  : http://www.pragma-ade.nl
>>> <http://www.pragma-ade.nl/> / http://context.aanhet.net
>>> <http://context.aanhet.net/>
>>> archive  : https://bitbucket.org/phg/context-mirror/commits/
>>> wiki     : http://contextgarden.net <http://contextgarden.net/>
>>> ___________________________________________________________________________________
>> 
>> 
>> 
>> ___________________________________________________________________________________
>> If your question is of interest to others as well, please add an entry to the Wiki!
>> 
>> maillist : ntg-context at ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
>> webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
>> archive  : https://bitbucket.org/phg/context-mirror/commits/
>> wiki     : http://contextgarden.net
>> ___________________________________________________________________________________
>> 
> 
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
> 
> maillist : ntg-context at ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
> archive  : https://bitbucket.org/phg/context-mirror/commits/
> wiki     : http://contextgarden.net
> ___________________________________________________________________________________

Taco Hoekwater
Elvenkind BV






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