Section 3: library functions
CURLOPT_TFTP_BLKSIZE – TFTP block size Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TFTP_BLKSIZE, long blocksize); DescriptionSpecify blocksize to use for TFTP data transmission. Valid range as per RFC2348 is 8-65464 bytes. The default of 512 bytes will be used if this option is not specified. The specified block size will only be used pending support by the…
CURLOPT_TELNETOPTIONS – custom telnet options Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TELNETOPTIONS, struct curl_slist *cmds); DescriptionProvide a pointer to a curl_slist with variables to pass to the telnet negotiations. The variables should be in the format <option=value>. libcurl supports the options ‘TTYPE’, ‘XDISPLOC’ and ‘NEW_ENV’. See the TELNET standard for details. DefaultNULL ProtocolsTELNET ExampleTODO AvailabilityAlong with TELNET…
CURLOPT_TCP_NODELAY – set the TCP_NODELAY option Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TCP_NODELAY, long nodelay); DescriptionPass a long specifying whether the TCP_NODELAY option is to be set or cleared (1 = set, 0 = clear). The option is cleared by default. This will have no effect after the connection has been established. Setting this option will…
CURLOPT_TCP_KEEPINTVL – set TCP keep-alive interval Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TCP_KEEPINTVL, long interval); DescriptionPass a long. Sets the interval, in seconds, that the operating system will wait between sending keepalive probes. Not all operating systems support this option. (Added in 7.25.0) DefaultProtocolsExampleTODO AvailabilityAlways Return ValueReturns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if…
CURLOPT_TCP_KEEPIDLE – set TCP keep-alive idle time wait Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TCP_KEEPIDLE, long delay); DescriptionPass a long. Sets the delay, in seconds, that the operating system will wait while the connection is idle before sending keepalive probes. Not all operating systems support this option. Default? ProtocolsAll ExampleTODO AvailabilityAdded in 7.25.0 Return ValueReturns CURLE_OK…
CURLOPT_TCP_KEEPALIVE – enable TCP keep-alive probing Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TCP_KEEPALIVE, long probe); DescriptionPass a long. If set to 1, TCP keepalive probes will be sent. The delay and frequency of these probes can be controlled by the CURLOPT_TCP_KEEPIDLE(3) and CURLOPT_TCP_KEEPINTVL(3) options, provided the operating system supports them. Set to 0 (default behavior) to…
CURLOPT_STDERR – redirect stderr to another stream Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_STDERR, FILE *stream); DescriptionPass a FILE * as parameter. Tell libcurl to use this stream instead of stderr when showing the progress meter and displaying CURLOPT_VERBOSE(3) data. Defaultstderr ProtocolsAll ExampleTODO AvailabilityAlways Return ValueReturns CURLE_OK See AlsoCURLOPT_VERBOSE(3), CURLOPT_NOPROGRESS(3),
CURLOPT_SSL_VERIFYPEER – verify the peer’s SSL certificate Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_VERIFYPEER, long verify); DescriptionPass a long as parameter to enable or disable. This option determines whether curl verifies the authenticity of the peer’s certificate. A value of 1 means curl verifies; 0 (zero) means it doesn’t. When negotiating a TLS or SSL connection,…
CURLOPT_SSL_VERIFYHOST – verify the certificate’s name against host Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_VERIFYHOST, long verify); DescriptionPass a long as parameter specifying what to verify. This option determines whether libcurl verifies that the server cert is for the server it is known as. When negotiating TLS and SSL connections, the server sends a certificate indicating…
CURLOPT_SSL_SESSIONID_CACHE – enable/disable use of the SSL session-ID cache Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_SESSIONID_CACHE, long enabled);DescriptionPass a long set to 0 to disable libcurl’s use of SSL session-ID caching. Set this to 1 to enable it. By default all transfers are done using the cache enabled. While nothing ever should get hurt by attempting…
CURLOPT_SSL_OPTIONS – set SSL behavior options Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_OPTIONS, long bitmask); DescriptionPass a long with a bitmask to tell libcurl about specific SSL behaviors. CURLSSLOPT_ALLOW_BEAST is the only supported bit and by setting this the user will tell libcurl to not attempt to use any workarounds for a security flaw in the…
CURLOPT_SSL_ENABLE_NPN – enable NPN Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_ENABLE_NPN, long npn); DescriptionPass a long as parameter, 0 or 1 where 1 is for enable and 0 for disable. This option enables/disables NPN in the SSL handshake (if the SSL backend libcurl is built to use supports it), which can be used to negotiate http2….
CURLOPT_SSL_ENABLE_ALPN – enable ALPN Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_ENABLE_ALPN, long npn); DescriptionPass a long as parameter, 0 or 1 where 1 is for enable and 0 for disable. This option enables/disables ALPN in the SSL handshake (if the SSL backend libcurl is built to use supports it), which can be used to negotiate http2….
CURLOPT_SSL_CTX_FUNCTION – openssl specific callback to do SSL magic Synopsis#include <curl/curl.h> CURLcode ssl_ctx_callback(CURL *curl, void *ssl_ctx, void *userptr); CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CTX_FUNCTION, ssl_ctx_callback);DescriptionThis option only works for libcurl powered by OpenSSL. If libcurl was built against another SSL library, this functionality is absent. Pass a pointer to your callback function, which should match the prototype…
CURLOPT_SSL_CTX_DATA – custom pointer passed to ssl_ctx callback Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CTX_DATA, void *pointer); DescriptionData pointer to pass to the ssl context callback set by the option CURLOPT_SSL_CTX_FUNCTION(3), this is the pointer you’ll get as third parameter. DefaultNULL ProtocolsAll TLS based protocols: HTTPS, FTPS, IMAPS, POP3, SMTPS etc. ExampleTODO AvailabilityAdded in 7.11.0. Only…
CURLOPT_SSL_CIPHER_LIST – specify ciphers to use for TLS Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CIPHER_LIST, char *list); DescriptionPass a char *, pointing to a zero terminated string holding the list of ciphers to use for the SSL connection. The list must be syntactically correct, it consists of one or more cipher strings separated by colons. Commas…
CURLOPT_SSLVERSION – set preferred TLS/SSL version Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLVERSION, long version); DescriptionPass a long as parameter to control which version of SSL/TLS to attempt to use. Use one of the available defines for this purpose. The available options are: CURL_SSLVERSION_DEFAULT The default action. This will attempt to figure out the remote SSL…
CURLOPT_SSLKEYTYPE – set type of the private key file Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLKEYTYPE, char *type); DescriptionPass a pointer to a zero terminated string as parameter. The string should be the format of your private key. Supported formats are "PEM", "DER" and "ENG". The format "ENG" enables you to load the private key from…
CURLOPT_SSLKEY – specify private keyfile for TLS and SSL client cert Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLKEY, char *keyfile); DescriptionPass a pointer to a zero terminated string as parameter. The string should be the file name of your private key. The default format is "PEM" and can be changed with CURLOPT_SSLKEYTYPE(3). (iOS and Mac OS…
CURLOPT_SSLENGINE_DEFAULT – make SSL engine default Synopsis#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLENGINE_DEFAULT, long val); DescriptionPass a long set to 1 as parameter. Sets the actual crypto engine as the default for (asymmetric) crypto operations. If the crypto device cannot be set, CURLE_SSL_ENGINE_SETFAILED is returned. DefaultNone ProtocolsAll TLS based protocols: HTTPS, FTPS, IMAPS, POP3, SMTPS etc….