gpfs_iread() subroutine

Reads a file opened by gpfs_iopen().

Library

GPFS Library (libgpfs.a for AIX®, libgpfs.so for Linux®)

Synopsis

#include <gpfs.h>
int gpfs_iread(gpfs_ifile_t *ifile, 
               void *buffer, 
               int bufferSize, 
               gpfs_off64_t *offset);

Description

The gpfs_iread() subroutine reads data from the file indicated by the ifile parameter returned from gpfs_iopen(). This subroutine reads data beginning at parameter offset and continuing for bufferSize bytes into the buffer specified by buffer. If successful, the subroutine returns a value that is the length of the data read, and sets parameter offset to the offset of the next byte to be read. A return value of 0 indicates end-of-file.

For an overview of using gpfs_iread() in a backup application, see Using APIs to develop backup applications.

Note: Compile any program that uses this subroutine with the -lgpfs flag from the following library:

libgpfs.a for AIX
libgpfs.so for Linux

Parameters

ifile: Pointer to gpfs_ifile_t from gpfs_iopen().
buffer: Buffer for the data to be read.
bufferSize: Size of the buffer (that is, the amount of data to be read).
offset: Offset of where within the file to read. If gpfs_iread() is successful, offset is updated to the next byte after the last one that was read.

Exit status

If the gpfs_iread() subroutine is successful, it returns the number of bytes read.

If the gpfs_iread() subroutine is unsuccessful, it returns a value of -1 and sets the global error variable errno to indicate the nature of the error.

Exceptions

None.

Error status

Error codes include but are not limited to the following:

EISDIR: The specified file is a directory.
EINVAL: Missing or incorrect parameter.
ENOSYS: The gpfs_iread() subroutine is not available.
EPERM: The caller does not have superuser privileges.
ESTALE: Cached file system information was not valid.
GPFS_E_INVAL_IFILE: Incorrect ifile parameter.
GPFS_E_ISLNK: The specified file is a symlink. Use gpfs_ireadlink subroutine on symlink.

Location

/usr/lpp/mmfs/lib/libgpfs.a for AIX

/usr/lpp/mmfs/lib/libgpfs.so for Linux