FCLEAR(2,L)                 AIX Technical Reference                 FCLEAR(2,L)



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fclear



PURPOSE

Clears space in a file, freeing unused disk space.

SYNTAX

long fclear (fildes, nbytes)
int fildes;
unsigned long nbytes;

DESCRIPTION

The fclear system call zeros the number of bytes specified by the nbytes
parameter starting at the current position of the file open on file descriptor
fildes.  This function differs from the logically equivalent write operation in
that it returns full blocks of binary zeros to the file system, constructing
holes in the file.  The seek pointer of the file is advanced by nbytes.

If you fclear past the end of a file, the rest of the file is cleared, and the
seek pointer is advanced by nbytes.  The file size is updated to include this
new hole, which leaves the current file position at the byte immediately beyond
the new end-of-file.  Successful completion of the fclear system call clears
the set-user-ID and set-group-ID attributes of the file.

RETURN VALUE

Upon successful completion, a value of nbytes is returned.  If the fclear
system call fails, a value of -1 is returned, and errno is set to indicate the
error.

ERROR CONDITIONS

The fclear system call fails if one or more of the following are true:

EIO       I/O error.

EBADF     The fildes option is not a valid file descriptor open for writing.

EINVAL    The file is a FIFO, directory, or special file.

EAGAIN    The write operation in fclear failed, due to an enforced write lock
          on the file.

If the Transparent Computing Facility is installed on your system, fclear can
also fail if one or more of the following are true:





Processed November 7, 1990        FCLEAR(2,L)                                 1

FCLEAR(2,L)                 AIX Technical Reference                 FCLEAR(2,L)



ESITEDN1  The storage site is down or has gone down since this file descriptor
          was issued.

ESITEDN2  The operation was terminated because a site failed.

RELATED INFORMATION

In this book:  "ftruncate, truncate."















































Processed November 7, 1990        FCLEAR(2,L)                                 2