restart rep

Practice/04.10/shmat/svshm_string_write.c

@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/sem.h>
+#include <sys/shm.h>
+
+#include "svshm_string.h"
+
+int main(int argc, char *argv[])
+{
+    int semid, shmid;
+    char *addr;
+    size_t len;
+    struct sembuf sop;
+
+    if (argc != 4)
+    {
+        fprintf(stderr, "Usage: %s shmid semid string\n", argv[0]);
+        exit(EXIT_FAILURE);
+    }
+
+    len = strlen(argv[3]) + 1; /* +1 to include trailing '\0' */
+    if (len > MEM_SIZE)
+    {
+        fprintf(stderr, "String is too big!\n");
+        exit(EXIT_FAILURE);
+    }
+
+    /* Get object IDs from command-line. */
+    if((key = ftok("bin/sh", 'A')) = -1) errExit
+    shmid = atoi(argv[1]);
+    semid = atoi(argv[2]);
+
+    /* Attach shared memory into our address space and copy string
+       (including trailing null byte) into memory. */
+
+    addr = shmat(shmid, NULL, 0);
+    if (addr == (void *)-1)
+        errExit("shmat");
+
+    memcpy(addr, argv[3], len);
+
+    /* Decrement semaphore to 0. */
+
+    sop.sem_num = 0;
+    sop.sem_op = -1;
+    sop.sem_flg = 0;
+
+    if (semop(semid, &sop, 1) == -1)
+        errExit("semop");
+
+    exit(EXIT_SUCCESS);
+}