CURLOPT_LOGIN_OPTIONS(3)

💅 CURLOPT_LOGIN_OPTIONS(3) — the libcurl manual, bestie edition 🎀

okay so this is a page straight out of the libcurl Library Functions Manual, and it's all about one very specific little setopt. she's niche, she's protocol-specific, and she's literally the key to telling your mail server how you wanna log in. let's get into it ✨

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🌸 NAME 🌸

CURLOPT_LOGIN_OPTIONS — login options. that's it, that's the vibe. it's the option where you drop your protocol-specific login tea ☕

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✨ SYNOPSIS ✨

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_LOGIN_OPTIONS, char *options);

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🦋 DESCRIPTION 🦋

so you pass a char pointer as the parameter, and that pointer should be pointing at the null-terminated options string you wanna use for the transfer. simple. clean. iconic. 💫

if you want the full lore on login options, the manual says go read RFC 2384, RFC 5092 and the IETF draft draft-earhart-url-smtp-00.txt. it's giving "required reading for the girlies who want the deep lore" 📚

CURLOPT_LOGIN_OPTIONS(3) is your girl for setting protocol-specific login options, like the preferred authentication mechanism via "AUTH=NTLM" or "AUTH=*". and bestie, please use her in conjunction with the CURLOPT_USERNAME(3) option — they're a matching set, like a two-piece outfit 🫶

since 8.2.0, IMAP supports the login option "AUTH=+LOGIN". with this option, curl uses the plain (not SASL) LOGIN IMAP command even if the server advertises SASL authentication. now — care should be taken in using this option, because it sends your password in plain text. 😭 no cap, that's a security vibe check. and it does not work if the IMAP server disables the plain LOGIN (e.g. to prevent password snooping). the server said "nope, not today" 🚫

⚠️ the good news: the application does not have to keep the string around after setting this option. curl handles it. you can let it go, queen — you don't gotta hover 💅

using this option multiple times makes the last set string override the previous ones. so yeah, last one wins, main character energy only. set it to NULL to disable its use again. bye bye 👋

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🎀 DEFAULT 🎀

NULL

(yeah. nothing. empty. she starts unset, as she should 🌸)

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🌈 PROTOCOLS 🌈

this functionality affects imap, ldap, pop3 and smtp — the quad squad of mail-and-directory protocols 💌

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🔥 EXAMPLE 🔥

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "smtp://example.com/");
    curl_easy_setopt(curl, CURLOPT_LOGIN_OPTIONS, "AUTH=*");
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

look at her go 😭 init, set the URL, set AUTH=*, perform, cleanup. the full lifecycle. we love a complete example 🫶

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🧚 HISTORY 🧚

support for OpenLDAP was added in 7.82.0. so she got an upgrade, and she ate 💅

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⭐ AVAILABILITY ⭐

added in curl 7.34.0. she's been around a minute, she's a legacy icon 👑

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💜 RETURN VALUE 💜

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK — slay, no notes. non-zero means an error occurred, and you should go see libcurl-errors(3) for the full breakdown of what went wrong 🔍

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🍓 SEE ALSO 🍓

• CURLOPT_PASSWORD(3)
• CURLOPT_USERNAME(3)

(the friendship trio — go read them next, iykyk 🫶)

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that's the whole page, bestie — every flag, every default, every warning, preserved with love. 💖

mwah 💋 — this gem came from libcurl, last touched 2026-10-12, and the page you just read is CURLOPT_LOGIN_OPTIONS(3). go forth and authenticate responsibly ✨