CODEWITHSUNDEEP
qnx
harishaj90
harishaj90

Reputation: 132

can I use shm_open instead of shmget on QNX

I am new to QNX platform, and we are porting Linux project to QNX. and found code related to shared memory creating in linux using shmget system call. but shmget not present in QNX. and I saw similar call shm_open, I don't know difference b/w both.

My straight question is like, should I use shm_open instead of shmget in QNX platform ? If yes, how ? if not, why not ?

Upvotes: 0

Views: 1227

Answers (1)

Shaibal
Shaibal

Reputation: 925

First of all QNX does NOT support the shmget() API.

You will need to use shm_open() instead.

Below is a sample program from online QNX documentation
that demonstrates the proper use of shm_open() on QNX:

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <limits.h>
#include <sys/mman.h>

int main( int argc, char** argv )
{
    int fd;
    unsigned* addr;

    /*
     * In case the unlink code isn't executed at the end
     */
    if( argc != 1 ) {
        shm_unlink( "/bolts" );
        return EXIT_SUCCESS;
    }

    /* Create a new memory object */
    fd = shm_open( "/bolts", O_RDWR | O_CREAT, 0777 );
    if( fd == -1 ) {
        fprintf( stderr, "Open failed:%s\n",
            strerror( errno ) );
        return EXIT_FAILURE;
    }

    /* Set the memory object's size */
    if( ftruncate( fd, sizeof( *addr ) ) == -1 ) {
        fprintf( stderr, "ftruncate: %s\n",
            strerror( errno ) );
       return EXIT_FAILURE;
    }

    /* Map the memory object */
    addr = mmap( 0, sizeof( *addr ),
            PROT_READ | PROT_WRITE,
            MAP_SHARED, fd, 0 );
    if( addr == MAP_FAILED ) {
        fprintf( stderr, "mmap failed: %s\n",
            strerror( errno ) );
        return EXIT_FAILURE;
    }

    printf( "Map addr is 0x%08x\n", addr );

    /* Write to shared memory */
    *addr = 1;

    /*
     * The memory object remains in
     * the system after the close
     */
    close( fd );

    /*
     * To remove a memory object
     * you must unlink it like a file.
     *
     * This may be done by another process.
     */
    shm_unlink( "/bolts" );

    return EXIT_SUCCESS;
}

Hope this helps.

Upvotes: 1

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