wrshm.c

来自「基于网络编程的例子」· C语言 代码 · 共 49 行

/*
 * wrshm.c - Write data to a shared memory segment
 */
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <ctype.h>

#define BUFSZ 4096

int main(int argc, char *argv[])
{
    int shmid;			/* Segment ID */
    char *shmbuf;		/* Address in process */
    int c, i;
    
    /* Expect an segment id on the command-line */
    if(argc != 2) {
	puts("USAGE: wrshm <identifier>");
	exit(EXIT_FAILURE);
    }
    shmid = atoi(argv[1]);
    
    /* Attach the segment */
    if((shmbuf = shmat(shmid, 0, 0)) < (char *)0) {
	perror("shmat");
	exit(EXIT_FAILURE);
    }
    
    /* Size shmbuf appropriately */
    if((shmbuf = malloc(sizeof(char) * BUFSZ)) == NULL) {
	perror("malloc");
	exit(EXIT_FAILURE);
    }

    /* Write user input to the segment */
    i = 0;
    while((c = getchar()) != EOF) {
	*(shmbuf++) = c;
	++i;
    }
    write(STDOUT_FILENO, shmbuf, i);
    printf("wrote %d characters to shared memory\n", i);
    exit(EXIT_SUCCESS);
}