dirs_links/view_symlink.c

This is dirs_links/view_symlink.c (Listing 18-4, page 369), 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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/* view_symlink.c

   Demonstrate the use of readlink() and realpath() to read and display
   the contents of a symbolic link.
*/
#include <sys/stat.h>
#include <limits.h>             /* For definition of PATH_MAX */
#include "tlpi_hdr.h"

#define BUF_SIZE PATH_MAX
int
main(int argc, char *argv[])
{
    struct stat statbuf;
    char buf[BUF_SIZE];
    ssize_t numBytes;

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

    /* User lstat() to check whether the supplied pathname is
       a symbolic link. Alternatively, we could have checked to
       whether readlink() failed with EINVAL. */

    if (lstat(argv[1], &statbuf) == -1)
        errExit("lstat");

    if (!S_ISLNK(statbuf.st_mode))
        fatal("%s is not a symbolic link", argv[1]);

    numBytes = readlink(argv[1], buf, BUF_SIZE - 1);
    if (numBytes == -1)
        errExit("readlink");
    buf[numBytes] = '\0';                       /* Add terminating null byte */
    printf("readlink: %s --> %s\n", argv[1], buf);

    if (realpath(argv[1], buf) == NULL)
        errExit("realpath");
    printf("realpath: %s --> %s\n", argv[1], buf);

    exit(EXIT_SUCCESS);
}

 

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