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gpfs_iread() Subroutine
Name
gpfs_iread() - Reads a file opened by gpfs_iopen().
Library
GPFS Library (libgpfs.a for AIX, libgpfs.so for Linux)
Synopsis
#include
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” on page 24.
Notes:
1. Compile any program that uses this subroutine with the -lgpfs flag from the following library:
v libgpfs.a for AIX
v 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
EISDIR The specified file is a directory.
ENOSYS The gpfs_iread() subroutine is not available.
Chapter 9. GPFS programming interfaces 319