72 lines
2.0 KiB
Groff
72 lines
2.0 KiB
Groff
.\" generated by cd2nroff 0.1 from CURLOPT_HEADERDATA.md
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.TH CURLOPT_HEADERDATA 3 "2025-07-07" libcurl
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.SH NAME
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CURLOPT_HEADERDATA \- pointer to pass to header callback
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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_HEADERDATA, void *pointer);
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.fi
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.SH DESCRIPTION
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Pass a \fIpointer\fP to be used to write the header part of the received data
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to.
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If \fICURLOPT_WRITEFUNCTION(3)\fP or \fICURLOPT_HEADERFUNCTION(3)\fP is used,
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\fIpointer\fP is passed in to the respective callback.
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If neither of those options are set, \fIpointer\fP must be a valid FILE * and
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it is used by a plain fwrite() to write headers to.
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If you are using libcurl as a Windows DLL, you \fBMUST\fP use a
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\fICURLOPT_WRITEFUNCTION(3)\fP or \fICURLOPT_HEADERFUNCTION(3)\fP if you set
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this option or you might experience crashes.
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.SH DEFAULT
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NULL
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.SH PROTOCOLS
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This functionality affects all supported protocols
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.SH EXAMPLE
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.nf
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struct my_info {
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int shoesize;
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char *secret;
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};
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static size_t header_callback(char *buffer, size_t size,
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size_t nitems, void *userdata)
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{
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struct my_info *i = userdata;
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printf("shoe size: %d\\n", i->shoesize);
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/* now this callback can access the my_info struct */
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return nitems * size;
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}
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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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struct my_info my = { 10, "the cookies are in the cupboard" };
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, header_callback);
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/* pass in custom data to the callback */
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curl_easy_setopt(curl, CURLOPT_HEADERDATA, &my);
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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 AVAILABILITY
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Added in curl 7.10
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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_HEADERFUNCTION (3),
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.BR CURLOPT_WRITEFUNCTION (3),
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.BR curl_easy_header (3)
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