hdfsPwrite()

Supported by libMapRClient for hadoop-2.x

Writes starting at a specified position in an open file.

Whereas hdfsWrite() increments the current offset by the amount of bytes returned by the API (except in case of error), hdfsPwrite() does not change the value of current offset. If the current offset before the call to hdfsPwrite() is 0 and you specify the offset 10 for the write operation, after the write the current offset remains 0.

If a call to hdfsPwrite() specifies an offset that is past the end of the file, the result is a hole in the file between the previous end of the file and the offset at which the write begins.

You can obtain the size of a file in bytes by calling hdfsGetPathInfo().

Flushes to the server happen automatically at intervals during a write operation. After a write operation is finished, either call hdfsFlush() explicitly or call hdfsFlush() implicitly by calling hdfsCloseFile() to be sure that any data remaining in the write buffer is flushed.

On error, pending write buffers are flushed to the server.

Signature

tSize hdfsPwrite(hdfsFS fs, hdfsFile file, tOffset position, const void* buffer, tSize length)

Parameters

Parameter Description
fs The handle of the filesystem where the file is located. Obtain this handle with one of the hdfsConnect() APIs.
file The handle of the file. Obtain this handle with one of the hdfsOpenFile() APIs.
position The offset at which to start writing.
buffer The data to write.
length The number of bytes to write. The maximum length is the maximum size of tSize.

Return Value

Returns the number of bytes written, -1 on error.

Check errno for error codes and meanings.