hdfsOpenFile()

Supported by libMapRClient for hadoop-2.x

Opens a file in the specified mode. Creates the file and intermediate directories if they do not exist.

Requires a valid filesystem handle, which one of the hdfsConnect() APIs can provide.

Before the call to hdfsOpenFile(), hdfsExists() can check that the file exists, if a check is needed.

After finishing work on a file, call hdfsCloseFile() to free the memory that is associated with the file.

Signature

hdfsFile hdfsOpenFile(hdfsFS fs, const char* path, int flags, int bufferSize, short replication, tSize blocksize)

Parameters

Parameter Description
fs The handle of the filesystem where the file is located. Obtain this handle with one of the hdfsConnect() APIs.
path The full path to the file.
flags One of the following values. These flags are included in the fcntl.h header file.
O_RDONLY
Opens the file in read-only mode with the current offset at 0.
O_RDWR
Opens the file in read-write mode. If the file already exists, it is truncated to offset 0, effectively deleting the content of the file to offset 0.
O_RDWR | O_APPEND
Opens the file in read-write mode with the current offset at 0. Writing to the file with hdfsWrite() appends the written data to the end of the file. Data written with hdfsPwrite() is not appended, but written starting at the offset specified in the call to that API.
O_WRONLY
Opens the file in write-only mode. If the file already exists, it is truncated to offset 0, effectively deleting the content of the file.
O_WRONLY | O_APPEND
Opens the file in write-only mode with the current offset at 0. Writing to the file with hdfsWrite() appends the written data to the end of the file. Data written with hdfsPwrite() is not appended, but written starting at the offset specified in the call to that API.
bufferSize Ignored for files on MapR file system
replication Ignored for files on MapR file system
blocksize The size of chunks for the file in bytes. Specify 0 if you want to use the value that is specified for the fs.mapr.block.size parameter in the /opt/mapr/hadoop/hadoop-2.x/etc/hadoop/core-site.xml file on the client (if the client is using the libMapRClient version of hadoop-2.x). If this parameter is not set in core-site.xml, the default value is taken from the directory’s .dfs_attrributes file.

Return Value

Returns the handle to the open file or NULL on error.

Check errno for error codes and meanings.