dirs_links/view_symlink.c

+/* 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);
 }