Call a Java program from a C program in Linux

Question

On a CentOS 7 server, I have a Java program /path/to/parent/bin/mainpackage/SendText.class that works perfectly when I call it from a c program located at /path/to/parent/bin using the syntax:

system("java -cp .:\"/path/to/parent/dependencies/*\" mainpackage.SendText username pincode");

But the problem is that the C program cannot be located in /path/to/parent/bin. Instead, the C program must be located in /path/to/parent/. How can I change the syntax so that the Java program will run when called from /path/to/parent/?

Here is what I have done to set things up so far:

The Java program was compiled from /path/to/anotherparent/ using the command

javac -d bin -cp .:/path/to/anotherparent/dependencies/twilio-java-sdk-3.4.5.jar:/path/to/anotherparent/dependencies/httpcore-4.1.2.jar SendText.java

I then created the destination and copied SendText.class and its dependencies to the destination as follows:

[user@domain somedir]$ mkdir /path/to/parent/bin/
[user@domain somedir]$ mkdir /path/to/parent/bin/mainpackage
[user@domain somedir]$ sudo cp /home/username/javacode/bin/mainpackage/SendText.class /path/to/parent/bin/mainpackage
[user@domain somedir]$ sudo mkdir /path/to/parent/dependencies
[user@domain somedir]$ sudo cp -R /home/username/javacode/dependencies/* /path/to/parent/dependencies

Next, I created the C program atest.c in /path/to/parent/ as follows:

[user@domain somedir]$ cd /path/to/parent
[user@domain parent]$ sudo nano atest.c

int main (void){
    char jcmd[256] = "java -cp .:\"/path/to/parent/dependencies/*\" mainpackage.SendText username pincode";
    printf(jcmd);
    system(jcmd);
    return 0;
}

Ctrl-X to save the program

I compiled the C program and tried to run it from /path/to/parent/ as follows:

[user@domain parent]$ sudo cc atest.c -o atest
[user@domain parent]$ ./atest
Error: Could not find or load main class mainpackage.SendText
java -cp .:"/path/to/parent/dependencies/*" mainpackage.SendText username pincode

To confirm that the problem is the location of the C file, I did the following:

[user@domain parent]$ sudo cp atest bin
[user@domain parent]$ cd /path/to/parent/bin
[user@domain bin]$ ./atest

Program runs successfully from /path/to/parent/bin

So what do I change in order to get the Java program to run successfully when it is called from /path/to/parent/ with the command ./atest?

user207421 · Accepted Answer · 2015-08-28 00:44:59Z

1

javac -d bin ...

That means that bin, as an absolute path, must appear in the CLASSPATH when you run it. Better still, create a JAR file for the contents of bin, put it whenever you like, and provide the absolute path of the JAR file as a CLASSPATH element when you execute.

edited Aug 28, 2015 at 0:44

answered Aug 27, 2015 at 9:16

user207421

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