mmap/mmcat.c

This is mmap/mmcat.c (Listing 49-1, page 1022), an example from the book, The Linux Programming Interface.

The source code file is copyright 2022, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

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Function list (Bold in this list means a function is not static)

/* mmcat.c

   Use mmap() plus write() to display the contents of a file (specified
   as a command-line argument) on standard output.
*/
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "tlpi_hdr.h"
int
main(int argc, char *argv[])
{
    char *addr;
    int fd;
    struct stat sb;

    if (argc != 2 || strcmp(argv[1], "--help") == 0)
        usageErr("%s file\n", argv[0]);

    fd = open(argv[1], O_RDONLY);
    if (fd == -1)
        errExit("open");

    /* Obtain the size of the file and use it to specify the size of
       the mapping and the size of the buffer to be written */

    if (fstat(fd, &sb) == -1)
        errExit("fstat");

    /* Handle zero-length file specially, since specifying a size of
       zero to mmap() will fail with the error EINVAL */

    if (sb.st_size == 0)
        exit(EXIT_SUCCESS);

    addr = mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
    if (addr == MAP_FAILED)
        errExit("mmap");

    if (write(STDOUT_FILENO, addr, sb.st_size) != sb.st_size)
        fatal("partial/failed write");
    exit(EXIT_SUCCESS);
}

 

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