curl/docs/libcurl/opts/CURLOPT_USE_SSL.md
Viktor Szakats d01d2ec9f1
docs: add CURLOPT type change history, drop casts where present
Some CURLOPT constants defined in the curl public headers were initially
enums (= ints), or macros with bare numeric values. Recent curl releases
upgraded them to `long` constants, to make them pass correctly to
`curl_easy_setop()` by default, i.e. without requiring a `(long)` cast.

This patch drops such casts from the examples embedded in the docs. At
the same time it documents which curl release made them `long` types,
to keep them useful when working with previous libcurl versions.

Also:
- drop a `(long)` cast that was never necessary.
- CURLOPT_ALTSVC_CTRL.md: bump local copy of macros to long.
- test1119: make it ignore symbols ending with an underscore, to skip
  wildcard, e.g. `**CURLAUTH_***`.

Closes #18130
2025-08-02 00:05:33 +02:00

97 lines
2 KiB
Markdown

---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_USE_SSL
Section: 3
Source: libcurl
See-also:
- CURLOPT_PROXY_SSLVERSION (3)
- CURLOPT_SSLVERSION (3)
- CURLOPT_SSL_OPTIONS (3)
Protocol:
- FTP
- SMTP
- POP3
- IMAP
Added-in: 7.17.0
---
# NAME
CURLOPT_USE_SSL - request using SSL / TLS for the transfer
# SYNOPSIS
~~~c
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_USE_SSL, long level);
~~~
# DESCRIPTION
Pass a long using one of the values from below, to make libcurl use your
desired *level* of SSL for the transfer.
These are all protocols that start out plain text and get "upgraded" to SSL
using the STARTTLS command.
This is for enabling SSL/TLS when you use FTP, SMTP, POP3, IMAP etc.
## CURLUSESSL_NONE
do not attempt to use SSL.
## CURLUSESSL_TRY
Try using SSL, proceed as normal otherwise. Note that server may close the
connection if the negotiation does not succeed.
## CURLUSESSL_CONTROL
Require SSL for the control connection or fail with *CURLE_USE_SSL_FAILED*.
## CURLUSESSL_ALL
Require SSL for all communication or fail with *CURLE_USE_SSL_FAILED*.
# DEFAULT
CURLUSESSL_NONE
# %PROTOCOLS%
# EXAMPLE
~~~c
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "ftp://example.com/dir/file.ext");
/* require use of SSL for this, or fail */
curl_easy_setopt(curl, CURLOPT_USE_SSL, CURLUSESSL_ALL);
/* Perform the request */
curl_easy_perform(curl);
}
}
~~~
# HISTORY
This option was known as CURLOPT_FTP_SSL up to 7.16.4. Supported by LDAP since
7.81.0. Fully supported by the OpenLDAP backend only.
**CURLUSESSL_*** enums became `long` types in 8.13.0, prior to this version
a `long` cast was necessary when passed to curl_easy_setopt(3).
# %AVAILABILITY%
# RETURN VALUE
curl_easy_setopt(3) returns a CURLcode indicating success or error.
CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
libcurl-errors(3).