CURLOPT_STDERR(3)

💅 CURLOPT_STDERR — redirect stderr to another stream 💅

okay bestie, so this is a page from the Library Functions Manual, and it's about CURLOPT_STDERR(3) — literally the glow-up where you tell libcurl to stop screaming into plain old stderr and scream into your stream instead. iconic behavior tbh 🎀

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✨ SYNOPSIS ✨

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_STDERR, FILE *stream);

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🌸 DESCRIPTION 🌸

So you pass a FILE * as the parameter. that's it, that's the vibe. 🫶

You're telling libcurl: "hey girl, use this stream instead of stderr when you're showing the progress meter and when you're displaying CURLOPT_VERBOSE(3) data." so all that chatty output gets rerouted to wherever you want — a file, a pipe, whatever, no cap. ✨

⚠️ okay but listen, this one's important: if you're using libcurl as a Windows DLL, this option causes an exception and a crash in the library, because it cannot access a FILE * passed on from the application. literally a whole crash bestie, not cute at all 😭 the work-around is to instead use CURLOPT_DEBUGFUNCTION(3). slay that instead 💅

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🌈 DEFAULT 🌈

stderr

like, the original main character. it stays the default unless you say otherwise.

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🦋 PROTOCOLS 🦋

This functionality affects all supported protocols — every single one, periodt 👑

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💖 EXAMPLE 💖

int main(void)
{
  CURL *curl = curl_easy_init();
  FILE *filep = fopen("dump", "wb");
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    curl_easy_setopt(curl, CURLOPT_STDERR, filep);

    curl_easy_perform(curl);
  }
}

look at that. opens dump for writing, points the stderr stream at it, and lets curl cook. ate and left no crumbs 🍓

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⭐ AVAILABILITY ⭐

Added in curl 7.1 — an elder icon, honestly. been serving since forever 👑

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🧚 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 — go check libcurl-errors(3) for the tea 🔥

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🎀 SEE ALSO 🎀

• CURLOPT_DEBUGFUNCTION(3)
• CURLOPT_NOPROGRESS(3)
• CURLOPT_VERBOSE(3)

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mwah 💜 that's the whole page. brought to you by libcurl, dated 2026-10-12, same date as always bestie — go forth and redirect your stderr responsibly ✨💅