pshm/pshm_write.c

+/* pshm_write.c
+
+   Usage: pshm_write shm-name string
+
+   Copy 'string' into the POSIX shared memory object named in 'shm-name'.
+
+   See also pshm_read.c.
+*/
 #include <fcntl.h>
 #include <sys/mman.h>
 #include "tlpi_hdr.h"
 
 int
 main(int argc, char *argv[])
 {
     int fd;
     size_t len;                 /* Size of shared memory object */
     char *addr;
 
     if (argc != 3 || strcmp(argv[1], "--help") == 0)
         usageErr("%s shm-name string\n", argv[0]);
 
     fd = shm_open(argv[1], O_RDWR, 0);      /* Open existing object */
     if (fd == -1)
         errExit("shm_open");
 
     len = strlen(argv[2]);
     if (ftruncate(fd, len) == -1)           /* Resize object to hold string */
         errExit("ftruncate");
     printf("Resized to %ld bytes\n", (long) len);
 
     addr = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
     if (addr == MAP_FAILED)
         errExit("mmap");
 
     if (close(fd) == -1)                    /* 'fd' is no longer needed */
         errExit("close");
 
     printf("copying %ld bytes\n", (long) len);
     memcpy(addr, argv[2], len);             /* Copy string to shared memory */
     exit(EXIT_SUCCESS);
 }