86 lines
2.5 KiB
Groff
86 lines
2.5 KiB
Groff
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.\" generated by cd2nroff 0.1 from CURLOPT_ALTSVC.md
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.TH CURLOPT_ALTSVC 3 "2025-07-07" libcurl
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.SH NAME
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CURLOPT_ALTSVC \- alt\-svc cache filename
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ALTSVC, char *filename);
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.fi
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.SH DESCRIPTION
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Pass in a pointer to a \fIfilename\fP to instruct libcurl to use that file as
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the Alt\-Svc cache to read existing cache contents from and possibly also write
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it back to after a transfer, unless \fBCURLALTSVC_READONLYFILE\fP is set in
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\fICURLOPT_ALTSVC_CTRL(3)\fP.
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Specify a blank filename ("") to make libcurl not load from a file at all.
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The application does not have to keep the string around after setting this
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option.
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Using this option multiple times makes the last set string override the
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previous ones. Set it to NULL to disable its use again.
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.SH SECURITY CONCERNS
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libcurl cannot fully protect against attacks where an attacker has write
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access to the same directory where it is directed to save files. This is
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particularly sensitive if you save files using elevated privileges.
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.SH DEFAULT
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NULL. The alt\-svc cache is not read nor written to file.
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.SH PROTOCOLS
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This functionality affects http only
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.SH EXAMPLE
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.nf
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int main(void)
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{
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CURL *curl = curl_easy_init();
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if(curl) {
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curl_easy_setopt(curl, CURLOPT_ALTSVC_CTRL, (long)CURLALTSVC_H1);
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curl_easy_setopt(curl, CURLOPT_ALTSVC, "altsvc-cache.txt");
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curl_easy_perform(curl);
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}
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}
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.fi
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.SH FILE FORMAT
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A text based file with one line per alt\-svc entry and each line consists of
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nine space\-separated fields.
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An example line could look like
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.nf
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h2 www.example.com 8443 h3 second.example.com 443 "20190808 06:18:37" 1 0
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.fi
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The fields of that line are:
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.IP h2
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ALPN id for the source origin
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.IP www.example.comp
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Hostname for the source origin
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.IP 8443
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Port number for the source origin
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.IP h3
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ALPN id for the destination host
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.IP second.example.com
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Hostname for the destination host
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.IP 443
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Port number for the destination host
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.IP 2019*
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Expiration date and time of this entry within double quotes. The date format
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is "YYYYMMDD HH:MM:SS" and the time zone is GMT.
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.IP 1
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Boolean (1 or 0) if "persist" was set for this entry
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.IP 0
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Integer priority value (not currently used)
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.SH AVAILABILITY
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Added in curl 7.64.1
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.SH RETURN VALUE
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\fIcurl_easy_setopt(3)\fP returns a CURLcode indicating success or error.
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CURLE_OK (0) means everything was OK, non\-zero means an error occurred, see
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\fIlibcurl\-errors(3)\fP.
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.SH SEE ALSO
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.BR CURLOPT_ALTSVC_CTRL (3),
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.BR CURLOPT_CONNECT_TO (3),
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.BR CURLOPT_COOKIEFILE (3),
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.BR CURLOPT_RESOLVE (3)
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