Hadoop accesses HDFs via the C API

When accessing HDFs through the C API of Hadoop, there are many problems with compiling and running, so here's a summary:

System: ubuntu11.04,hadoop-0.20.203.0

The sample code is provided in the official documentation to:

#include "hdfs.h" 

int main (int argc, char **argv) {

    Hdfsfs fs = Hdfsconnect ("default", 0);
    Const char* Writepath = "/tmp/testfile.txt";
    Hdfsfile WriteFile = Hdfsopenfile (FS, Writepath, o_wronly| O_creat, 0, 0, 0);
    if (!writefile) {
          fprintf (stderr, "Failed to open%s for writing!\n", Writepath);
          Exit ( -1);
    }
    char* buffer = "Hello, world!";
    Tsize num_written_bytes = Hdfswrite (FS, WriteFile, (void*) buffer, strlen (buffer) +1);
    if (Hdfsflush (FS, WriteFile)) {
           fprintf (stderr, "Failed to ' flush '%s\n", writepath); 
          Exit ( -1);
    }
   Hdfsclosefile (FS, WriteFile);
}

Compiling: The official website describes this

The Makefile for hdfs_test.c in the Libhdfs source directory (${hadoop_home}/src/c++/libhdfs/makefile) or something Li Ke
GCC Above_sample.c-i${hadoop_home}/src/c++/libhdfs-l${hadoop_home}/libhdfs-lhdfs-o above_sample

But I have tried two methods, no, the back is found to be less:

LIB =-l$ (hadoop_install)/c++/linux-i386-32/lib/
libjvm=/usr/lib/jvm/java-6-openjdk/jre/lib/i386/client/ Libjvm.so

So complete to Makefile is:

hadoop_install=/home/fzuir/hadoop-0.20.203.0
platform=linux-i386-32
java_home=/usr/lib/jvm/ java-6-openjdk/
cppflags=-i$ (hadoop_install)/src/c++/libhdfs
LIB =-l$ (hadoop_install)/c++/linux-i386-32 /lib/
libjvm=/usr/lib/jvm/java-6-openjdk/jre/lib/i386/client/libjvm.so
ldflags =-lhdfs

TestHdfs: TESTHDFS.C
	gcc testhdfs.c  $ (cppflags) $ (LIB) $ (ldflags) $ (LIBJVM)-O testhdfs clean

:
	rm Testhdfs

OK, the compilation passes, but the following error message appears when running:

1.

./testhdfs:error while loading shared libraries:xxx.so.0:cannot open Shared object file:no such file or directory

Workaround: Add the xxx.so.0 directory to the/etc/ld.so.conf, then/sbin/ldconfig–v it.

2.

Exception in thread "main" java.lang.noclassdeffounderror:org/apache/commons/configuration/configuration

...

Call to Org.apache.hadoop.fs.filesystem::get (URI, Configuration) failed!
Exception in thread "main" java.lang.NullPointerException
Call to get Configuration object from filesystem failed!

Workaround, modify the/etc/profile, and add the corresponding classpath:

hadoop_home=/home/fzuir/hadoop-0.20.203.0
Export path= $HADOOP _home/bin: $PATH
export classpath=.: $HADOOP _ Home/lib/commons-lang-2.4.jar: $HADOOP _home/hadoop-cor
e-1.0.1.jar: $HADOOP _home/lib/ Commons-logging-api-1.0.4.jar: $HADOOP _home/lib/comm
Ons-configuration-1.6.jar: $JAVA _home/lib: $JRE _home/lib : $HADOOP _home/contrib/stre
Aming/hadoop-streaming-1.0.1.jar: $CLASSPATH

Finally, congratulations, the problem has been solved.