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ISFDTYPE(3) Library Functions Manual ISFDTYPE(3)

isfdtype —
determine whether a file descriptor is of a specific type

#include <sys/stat.h>

int
isfdtype(int fd, int fdtype);

The isfdtype() function checks whether or not the file descriptor fd is of type fdtype.

A list of possible file types may be found in stat(2) and the <sys/stat.h> include file.

The isfdtype() function returns 1 if fd is of type fdtype and 0 if it is not. If isfdtype() fails, a value of -1 is returned and the global variable errno is set to indicate the error.

The following error codes may be set in errno:
[]
fd is not a valid open file descriptor.
[]
An I/O error occurred while reading from or writing to the file system.

stat(2)

The isfdtype() function first appeared in OpenBSD 3.3.
January 25, 2019 OpenBSD-current