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# PRFileDesc
A file descriptor used to represent any open file, such as a normal
file, an end point of a pipe, or a socket (end point of network
communication).
## Syntax
```{code}
#include <prio.h>
struct PRFileDesc {
PRIOMethods *methods;
PRFilePrivate *secret;
PRFileDesc *lower, *higher;
void (*dtor)(PRFileDesc *fd);
PRDescIdentity identity;
};
typedef struct PRFileDesc PRFileDesc;
```
### Parameters
`methods`
: The I/O methods table. See {ref}`PRIOMethods`.
`secret`
: Layer-dependent implementation data. See {ref}`PRFilePrivate`.
`lower`
: Pointer to lower layer.
`higher`
: Pointer to higher layer.
`dtor`
: A destructor function for the layer.
`identity`
: Identity of this particular layer. See {ref}`PRDescIdentity`.
## Description
The fields of this structure are significant only if you are
implementing a layer on top of NSPR, such as SSL. Otherwise, you use
functions such as {ref}`PR_Open` and {ref}`PR_NewTCPSocket` to obtain a file
descriptor, which you should treat as an opaque structure.
For more details about the use of {ref}`PRFileDesc` and related structures,
see [File Descriptor Types](I_O_Types#File_Descriptor_Types).