curl_easy_nextheader(3) Library Functions Manual curl_easy_nextheader(3)
NAME
curl_easy_nextheader - get the next HTTP header
SYNOPSIS
#include <curl/curl.h>
struct curl_header *curl_easy_nextheader(CURL *easy,
unsigned int origin,
int request,
struct curl_header *prev);
DESCRIPTION
This function lets an application iterate over all previously received
HTTP headers.
The origin argument is for specifying which headers to receive, as a
single HTTP transfer might provide headers from several different places
and they may then have different importance to the user and headers us-
ing the same name might be used. The origin is a bitmask for what header
sources you want. See the curl_easy_header(3) man page for the origin
descriptions.
The request argument tells libcurl from which request you want headers
from. A single transfer might consist of a series of HTTP requests and
this argument lets you specify which particular individual request you
want the headers from. 0 being the first request and then the number in-
creases for further redirects or when multi-state authentication is
used. Passing in -1 is a shortcut to "the last" request in the series,
independently of the actual amount of requests used.
It is suggested that you pass in the same origin and request when iter-
ating over a range of headers as changing the value mid-loop might give
you unexpected results.
If prev is NULL, this function returns a pointer to the first header
stored within the given scope (origin + request).
If prev is a pointer to a previously returned header struct,
curl_easy_nextheader(3) returns a pointer the next header stored within
the given scope. This way, an application can iterate over all available
headers.
The memory for the struct this points to, is owned and managed by
libcurl and is associated with the easy handle. Applications must copy
the data if they want it to survive subsequent API calls or the
life-time of the easy handle.
PROTOCOLS
This functionality affects http only
EXAMPLE
int main(void)
{
struct curl_header *prev = NULL;
struct curl_header *h;
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
curl_easy_perform(curl);
/* extract the normal headers from the first request */
while((h = curl_easy_nextheader(curl, CURLH_HEADER, 0, prev))) {
printf("%s: %s\n", h->name, h->value);
prev = h;
}
/* extract the normal headers + 1xx + trailers from the last request */
unsigned int origin = CURLH_HEADER| CURLH_1XX | CURLH_TRAILER;
while((h = curl_easy_nextheader(curl, origin, -1, prev))) {
printf("%s: %s\n", h->name, h->value);
prev = h;
}
}
}
AVAILABILITY
Added in curl 7.83.0
RETURN VALUE
This function returns the next header, or NULL when there are no more
(matching) headers or an error occurred.
If this function returns NULL when prev was set to NULL, then there are
no headers available within the scope to return.
SEE ALSO
curl_easy_header(3), curl_easy_perform(3)
libcurl 2026-07-12 curl_easy_nextheader(3)
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