# PR_Write

Writes a buffer of data to a file or socket.

## Syntax

```{code}
#include <prio.h>

PRInt32 PR_Write(
  PRFileDesc *fd,
  const void *buf,
  PRInt32 amount);
```

### Parameters

The function has the following parameters:

`fd`

: A pointer to the {ref}`PRFileDesc` object for a file or socket.

`buf`

: A pointer to the buffer holding the data to be written.

`amount`

: The amount of data, in bytes, to be written from the buffer.

### Returns

One of the following values:

- A positive number indicates the number of bytes successfully written.
- The value -1 indicates that the operation failed. The reason for the
  failure is obtained by calling {ref}`PR_GetError`.

## Description

The thread invoking {ref}`PR_Write` blocks until all the data is written or
the write operation fails. Therefore, the return value is equal to
either `amount` (success) or -1 (failure). Note that if {ref}`PR_Write`
returns -1, some data (less than `amount` bytes) may have been written
before an error occurred.