CURLOPT\_READDATA(3) Library Functions Manual CURLOPT\_READDATA(3)

# [NAME](#NAME)

CURLOPT\_READDATA - pointer passed to the read callback

# [SYNOPSIS](#SYNOPSIS)

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

# [DESCRIPTION](#DESCRIPTION)

Data *pointer* to pass to the file read function. If you use the [*CURLOPT\_READFUNCTION(3)*](/man/os/curl/CURLOPT_READFUNCTION.3) 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)*](/man/os/curl/CURLOPT_READFUNCTION.3) callback if you set this option, otherwise you might experience crashes.

# [DEFAULT](#DEFAULT)

stdin

# [PROTOCOLS](#PROTOCOLS)

This functionality affects all supported protocols

# [EXAMPLE](#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](#HISTORY)

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

# [AVAILABILITY](#AVAILABILITY)

Added in curl 7.9.7

# [RETURN VALUE](#RETURN_VALUE)

This returns CURLE\_OK.

# [SEE ALSO](#SEE_ALSO)

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

2026-09-24 libcurl

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Document: CURLOPT_READDATA(3) from curl 8.22.0-r3 (Chainguard OS)
Source: https://github.com/curl/curl.git