CURLOPT_FOLLOWLOCATION - follow HTTP 3xx redirects
#include <curl/curl.h> CURLcodecurl_easy_setopt(CURL *handle,CURLOPT_FOLLOWLOCATION, long mode);
This option tells the library to followLocation: header redirects that an HTTP server sends in a 30x response. TheLocation: header can specify a relative or an absolute URL to follow. The long parametermode instructs how libcurl should act on subsequent requests.
mode only had a single value (1L) for a long time that enables redirect following. Since8.13.0, two additional modes are also supported. See below.
When following redirects, libcurl issues another request for the new URL and follows subsequent newLocation: redirects all the way until no more such headers are returned or the maximum limit is reached.CURLOPT_MAXREDIRS is used to limit the number of redirects libcurl follows.
libcurl restricts what protocols it automatically follow redirects to. The accepted target protocols are set withCURLOPT_REDIR_PROTOCOLS_STR. By default libcurl allows HTTP, HTTPS, FTP and FTPS on redirects.
When following a redirect, the specific 30x response code also dictates which request method libcurl uses in the subsequent request: For 301, 302 and 303 responses libcurl switches method from POST to GET unlessCURLOPT_POSTREDIR instructs libcurl otherwise. All other redirect response codes make libcurl use the same method again.
For users who think the existing location following is too naive, too simple or just lacks features, it is easy to instead implement your own redirect follow logic with the use ofcurl_easy_getinfo'sCURLINFO_REDIRECT_URL option instead of usingCURLOPT_FOLLOWLOCATION.
By default, libcurl only sendsAuthentication: or explicitly setCookie: headers to the initial host given in the original URL, to avoid leaking username + password to other sites.CURLOPT_UNRESTRICTED_AUTH is provided to change that behavior.
Due to the way HTTP works, almost any header can be made to contain data a client may not want to pass on to other servers than the initially intended host and for all other headers than the two mentioned above, there is no protection from this happening when libcurl is told to follow redirects.
Pick one of the following modes:
Before8.13.0 this bit had no name and 1L was just the value to enable this option. This makes a set custom method be used in all HTTP requests, even after redirects.
When there is a custom request method set withCURLOPT_CUSTOMREQUEST, that set method replaces what libcurl would otherwise use. If a 301/302/303 response code is returned to signal a redirect, the method is changed from POST toGET. For 307/308, the custom method remains set and used.
Note that only POST (or a custom post) is changed to GET on 301/302, its not change PUT etc - and therefore also not when libcurl issues a custom PUT. A 303 response makes it switch to GET independently of the original method (except for HEAD).
To control for which of the 301/302/303 status codes libcurl shouldnot switch back to GET for when doing a custom POST, and instead keep the custom method, useCURLOPT_POSTREDIR.
If you prefer a custom POST method to be reset to exactly the methodPOST, use CURLFOLLOW_FIRSTONLY instead.
When there is a custom request method set withCURLOPT_CUSTOMREQUEST, that set method replaces what libcurl would otherwise use in the first outgoing request only. The second request is then done according to the redirect response code.
If you prefer your custom method to remain in use after a 307/308 redirect, use CURLFOLLOW_OBEYCODE instead.
Since libcurl changes method or not based on the specific HTTP response code, settingCURLOPT_CUSTOMREQUEST while following redirects may change what libcurl would otherwise do and if not that carefully may even make it misbehave sinceCURLOPT_CUSTOMREQUEST overrides the method libcurl would otherwise select internally.
Setting the CURLFOLLOW_OBEYCODE bit makes libcurlnot use the custom set method after redirects for 301, 302 and 303 responses. Unless theCURLOPT_POSTREDIR bits are set for those status codes.
0, disabled
This functionality affects http only
int main(void){ CURL *curl =curl_easy_init(); if(curl) { curl_easy_setopt(curl,CURLOPT_URL, "https://example.com"); /* example.com is redirected, so we tell libcurl to follow redirection */ curl_easy_setopt(curl,CURLOPT_FOLLOWLOCATION, 1L); curl_easy_perform(curl); }}Added in curl7.1
curl_easy_setopt returns a CURLcode indicating success or error.
CURLE_OK (0) means everything was OK, non-zero means an error occurred, seelibcurl-errors.
CURLINFO_REDIRECT_COUNT(3),CURLINFO_REDIRECT_URL(3),CURLOPT_POSTREDIR(3),CURLOPT_PROTOCOLS_STR(3),CURLOPT_REDIR_PROTOCOLS_STR(3),CURLOPT_UNRESTRICTED_AUTH(3)
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