Is there any way to run a java (.jar) program from a C or C ++ program?


I want to know if there is a way I can write a program .jar , and write a C / C ++ program that calls the JVM to execute the .jar file. It's possible? If so, can you give me an example code or an instruction how to do this?

asked by anonymous 25.07.2016 / 03:26

2 answers


The most standard solution would be to use the system() function of the default library stdlib.h .

BUT , from the point of view of *nix systems, the use of system() should be avoided:


1 - The call of the system() function executes the command interpreter   (shell), which makes it much slower than calling a fork()   followed by exec() ;


2 - This is a potential security risk if you pass as a parameter   an untrusted source string;


3 - Can not be used asynchronously, ie the system is   blocked waiting for the child process to return;


4 - Double fork() and exec() give us much more control before and between your   calls.

The following example exemplifies running .jar using fork() , exec() , and waitpid() calls on a Linux system.

Note that the child process prepares the environment by redirecting the output streams ( exec() and STDERR ) to two output files: STDOUT and stderr.txt .

The parent process stream is purposely blocked with the stdout.txt call, but could be "working" on another task:

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>

#define MAX_CMD_TAM  (1024)

int main( int argc, char * argv[] )
    char cmd[ MAX_CMD_TAM + 1 ] = {0};

    /* Verifica se o nome de arquivo .jar foi passado como parametro na linha de comando */
    if( argc != 2 )
        printf("Erro de sintaxe: %s [ARQUIVO_JAR]\n", argv[0] );
        return 1;

    /* Processo pai cria uma copia de si mesmo (cria um processo filho) */
    pid_t child = fork();

    /* Monta a linha de comando que sera executada */
    snprintf( cmd, MAX_CMD_TAM, "java -jar %s", argv[1] );

    if( child == 0 ) /* Fluxo do processo filho */
        /* Abre/Cria arquivos para substituirem as saidss padroes: STDOUT e STDERR */
        int fdout = open( "stdout.txt", O_RDWR | O_CREAT | O_APPEND, S_IRUSR | S_IWUSR );
        int fderr = open( "stderr.txt", O_RDWR | O_CREAT | O_APPEND, S_IRUSR | S_IWUSR );

        /* Redireciona o STDOUT e STDERR para os arquivos correspondentes */
        dup2( fdout, STDOUT_FILENO );
        dup2( fderr, STDERR_FILENO );

        /* Depois de duplicados, os descritores dos arquivos nao sao mais necessarios */

        /* Executa comando */
        execlp( cmd, NULL );
    else if( child > 0 ) /* Fluxo do processo pai */
        /* Processo pai aguarda a execucao do processo filho */
        printf( "Executando Comando: \"%s\"\n", cmd );

        printf( "Aguardando a execucao do processo filho...\n");

        printf("fork() falhou!\n");
        return 1;

    return 0;

/* fim-de-arquivo */

I hope I have helped!

25.07.2016 / 21:02

You can use the command line ( system() ):

 java -jar "arquivo.jar"

Depending on what you want to do, you can use JNI . It's pretty complicated.

25.07.2016 / 03:36