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Oracle® Big Data Connectors User's Guide
Release 2 (2.1)

Part Number E36961-05
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PDF · Mobi · ePub

hdfs.download

Copies a file from HDFS to the local file system.

Usage

hdfs.download(
        dfs.id,
        filename, 
        overwrite)

Arguments

dfs.id

The name of a file in HDFS. The file name can include a path that is either absolute or relative to the current path.

filename

The name of a file in the local file system where the data is copied.

overwrite

Controls whether the operation can overwrite an existing local file. Set to TRUE to overwrite filename, or FALSE to signal an error (default).

Usage Notes

This function provides the fastest and easiest way to copy a file from HDFS. No data transformations occur except merging multiple parts into a single file. The local file has the exact same data as the HDFS file.

Return Value

Local file name, or NULL if the copy failed

Example

This example displays a list of files in the current HDFS directory and copies ontime2000.DB to the local file system as /home/oracle/ontime2000.dat.

R> hdfs.ls()
[1] "ontime2000_DB" "ontime_DB"     "ontime_File"   "ontime_R"      "testdata.dat" 
R> tmpfile <- hdfs.download("ontime2000_DB", "/home/oracle/ontime2000.dat", overwrite=F)
R> tmpfile
[1] "/home/oracle/ontime2000.dat"