---
name: "CURLOPT_READDATA"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_READDATA"
---

# CURLOPT\_READDATA(3)

pointer passed to the read callback

## NAME

CURLOPT\_READDATA - pointer passed to the read callback

## SYNOPSIS

```
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_READDATA, void *pointer);
```

## DESCRIPTION

Data *pointer* to pass to the file read function. If you use the *[CURLOPT\_READFUNCTION(3)](/CURLOPT_READFUNCTION/3.md)* option, this is the pointer you get as input in the fourth argument to the callback.

If you do not specify a read callback but instead rely on the default internal read function, this data must be a valid readable FILE \* (cast to 'void \*').

If you are using libcurl as a DLL on Windows, you must use the *[CURLOPT\_READFUNCTION(3)](/CURLOPT_READFUNCTION/3.md)* callback if you set this option, otherwise you might experience crashes.

## DEFAULT

stdin

## PROTOCOLS

This functionality affects all supported protocols

## EXAMPLE

```
struct MyData {
  void *custom;
};
int main(void)
{
  CURL *curl = curl_easy_init();
  struct MyData my_data;
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    /* pass pointer that gets passed in to the
       CURLOPT_READFUNCTION callback */
    curl_easy_setopt(curl, CURLOPT_READDATA, &my_data);
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## HISTORY

This option was once known by the older name CURLOPT\_INFILE, the name *[CURLOPT\_READDATA(3)](/CURLOPT_READDATA/3.md)* was introduced in 7.9.7.

## AVAILABILITY

Added in curl 7.9.7

## RETURN VALUE

This returns CURLE\_OK.

## SEE ALSO

[**CURLOPT\_HEADERDATA**(3)](/CURLOPT_HEADERDATA/3.md), [**CURLOPT\_READFUNCTION**(3)](/CURLOPT_READFUNCTION/3.md), [**CURLOPT\_WRITEDATA**(3)](/CURLOPT_WRITEDATA/3.md), [**CURLOPT\_WRITEFUNCTION**(3)](/CURLOPT_WRITEFUNCTION/3.md)