CURLOPT_WRITEDATA(3)

💖 CURLOPT_WRITEDATA — curl_easy_setopt(3) energy ✨

okay so bestie, this page is from the libcurl library functions manual and it's literally about CURLOPT_WRITEDATA — the little pointer you hand over so curl knows where to dump the goods. stay with me, it's short and it slaps 🫶

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✨ NAME ✨

CURLOPT_WRITEDATA — the pointer that gets passed to the write callback 💅

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🌸 SYNOPSIS 🌸

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_WRITEDATA, void *pointer);

like, that's the whole vibe. a void * and a dream 💫

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🦋 DESCRIPTION 🦋

so this is a data pointer that gets passed to the write callback. that's it. that's the whole thing.

if you're using the CURLOPT_WRITEFUNCTION(3) option, then this is exactly the pointer you get back in that callback's fourth and last argument. no cap. the fourth argument is literally this guy 🎀

if you are not using a write callback, then heads up — you must make pointer a FILE * (cast to void *) because libcurl passes it straight to fwrite(3) when it writes data. so yeah, it's doing the work behind the scenes 👑

and the internal CURLOPT_WRITEFUNCTION(3) writes the data to the FILE * you gave with this option — or to stdout if you never set this option at all. stdout is the main character by default, periodt.

⚠️ okay this part matters, don't skip it: if you are using libcurl as a Windows DLL, you must also use CURLOPT_WRITEFUNCTION(3) if you set this option, or you might experience crashes 😭💀 like actual crashes. not a vibe. so don't do that to yourself.

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🍓 DEFAULT 🍓

stdout — she's always there for you, bestie 💖

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🌈 PROTOCOLS 🌈

this functionality affects all supported protocols. every single one. she's versatile like that ✨

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🧚 EXAMPLE 🧚

a common technique (and honestly kind of iconic) is to use the write callback to stash the incoming data into a dynamically growing allocated buffer — and then CURLOPT_WRITEDATA(3) points to a struct or to the buffer where you want the data stored. like in the getinmemory example:

https://curl.se/libcurl/c/getinmemory.html

go look at it, it's giving textbook behavior 📚💅

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💜 HISTORY 💜

this option was formerly known as CURLOPT_FILE — glow-up era — and the name CURLOPT_WRITEDATA(3) was added in 7.9.7 🌟

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👑 AVAILABILITY 👑

added in curl 7.9.7 🎀

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🔥 RETURN VALUE 🔥

this returns CURLE_OK. that's it. no drama, no surprises, just a clean little success return 😌

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💀 SEE ALSO 💀

• CURLOPT_HEADERDATA(3)
• CURLOPT_READDATA(3)
• CURLOPT_WRITEFUNCTION(3)

all the data-pointer besties, in one place 🫶

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okay that's the whole page!! published by libcurl on 2026-10-12, and the page itself is CURLOPT_WRITEDATA(3) — now go forth and point your pointers responsibly bestie, mwah 💋✨🌸