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CURLOPT_UNIX_SOCKET_PATH(3) curl_easy_setopt options
CURLOPT_UNIX_SOCKET_PATH - Unix domain socket
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_UNIX_SOCKET_PATH, char
Enables the use of Unix domain sockets as connection endpoint and sets
the path to path. If path is NULL, then Unix domain sockets are
disabled. An empty string will result in an error at some point, it
will not disable use of Unix domain sockets.
When enabled, curl will connect to the Unix domain socket instead of
establishing a TCP connection to a host. Since no TCP connection is
created, curl does not need to resolve the DNS hostname in the URL.
The maximum path length on Cygwin, Linux and Solaris is 107. On other
platforms it might be even less.
Proxy and TCP options such as CURLOPT_TCP_NODELAY(3) are not supported.
Proxy options such as CURLOPT_PROXY(3) have no effect either as these
are TCP-oriented, and asking a proxy server to connect to a certain
Unix domain socket is not possible.
The application does not have to keep the string around after setting
Default is NULL, meaning that no Unix domain sockets are used.
All protocols except for FILE and FTP are supported in theory. HTTP,
IMAP, POP3 and SMTP should in particular work (including their SSL/TLS
Given that you have an HTTP server running listening on
/tmp/httpd.sock, you can request an HTTP resource with:
curl_easy_setopt(curl_handle, CURLOPT_UNIX_SOCKET_PATH, "/tmp/httpd.sock");
curl_easy_setopt(curl_handle, CURLOPT_URL, "http://localhost/");
If you are on Linux and somehow have a need for paths larger than 107
bytes, you could use the proc filesystem to bypass the limitation:
int dirfd = open(long_directory_path_to_socket, O_DIRECTORY | O_RDONLY);
snprintf(path, sizeof(path), "/proc/self/fd/%d/httpd.sock", dirfd);
curl_easy_setopt(curl_handle, CURLOPT_UNIX_SOCKET_PATH, path);
/* Be sure to keep dirfd valid until you discard the handle */
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION
libcurl 7.79.1 September 8, 2021 CURLOPT_UNIX_SOCKET_PATH(3)