% cat -n file-line-directives.c
     1  #include <stdio.h>
     2  #include <stdlib.h>
     3
     4  int main(int argc, char **argv)
     5  {
     6          FILE *fd;
     7          char *errinfo = NULL;
     8
     9          errinfo = (char *) malloc (sizeof (char) * 50);
    10
    11          fd = fopen (argv[1], "r");
    12          if (fd == NULL)
    13          {
    14                  sprintf (errinfo, "Error at line %d of %s", (__LINE__ - 3), __FILE__);
    15                  perror (errinfo);
    16                  free (errinfo);
    17          }
    18          else
    19          {
    20                  printf ("file descriptor = %d", fileno(fd));
    21                  fclose (fd);
    22          }
    23
    24          return (0);
    25  }

% cc -o directives file-line-directives.c

% ./directives <- needs an argument ie., file name
Error at line 11 of file-line-directives.c: Bad address

% ./directives /tmp/nonexistingfile <- need an existing file name, to open it up for reading
Error at line 11 of file-line-directives.c: No such file or directory

% ls /tmp/*.log
/tmp/activity.log

%./directives /tmp/activity.log
file descriptor = 3

Posted by: Giri Mandalika.    # 8:45 PM Tweet