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Questions on codes

There're several questions i would like to ask for the following codes:

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <limits.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <unistd.h>


unsigned process_directory( char *theDir )
{
    	DIR *dir = NULL;
    	struct dirent entry;
    	struct dirent *entryPtr = NULL;
    	int retval = 0;
    	unsigned count = 0;
	char pathName[PATH_MAX + 1];

    	/* Open the given directory, if you can. */  
    	dir = opendir( theDir );
    	if( dir == NULL ) 
	{
        	printf( "Error opening %s: %s", theDir, strerror( errno ) );
        	return 0;
    	}
	
	retval = readdir_r( dir, &entry, &entryPtr );
    	while( entryPtr != NULL ) 
	{
        	struct stat entryInfo;
        
        	if( ( strncmp( entry.d_name, ".", PATH_MAX ) == 0 ) || ( strncmp( entry.d_name, "..", PATH_MAX ) == 0 ) ) 
		{
            		/* Short-circuit the . and .. entries. */
            		retval = readdir_r( dir, &entry, &entryPtr );
            		continue;
        	}
		(void)strncpy( pathName, theDir, PATH_MAX );
        	(void)strncat( pathName, "/", PATH_MAX );
        	(void)strncat( pathName, entry.d_name, PATH_MAX );
        
        	if( lstat( pathName, &entryInfo ) == 0 ) 
		{
            		count++;
                        // to check whether it is a directory
            		if( S_ISDIR( entryInfo.st_mode ) ) 
			{            
				/* directory */
                		printf( "processing %s/\n", pathName );
                		count += process_directory( pathName );
            		} 
                        // to check whether it is a file
			else if( S_ISREG( entryInfo.st_mode ) ) 
			{ 
				/* regular file */
                		printf( "\t%s has %lld bytes\n", pathName, (long long)entryInfo.st_size );
            		} 
                        // to check whether it is a symbolic link
			else if( S_ISLNK( entryInfo.st_mode ) ) 
			{ 
				/* symbolic link */
                		char targetName[PATH_MAX + 1];
                		if( readlink( pathName, targetName, PATH_MAX ) != -1 ) 
				{
                    			printf( "\t%s -> %s\n", pathName, targetName );
                		} 
				else 
				{
                    			printf( "\t%s -> (invalid symbolic link!)\n", pathName );
                		}
            		}
        	} 
		else 
		{
            		printf( "Error statting %s: %s\n", pathName, strerror( errno ) );
        	}
 		retval = readdir_r( dir, &entry, &entryPtr );
    	}
    
    	/* Close the directory and return the number of entries. */
    	(void)closedir( dir );
    	return count;
}

/* readdir_demo main()
 * 
 * Run through the specified directories, and pass them
 * to process_directory().
 */
int main( int argc, char **argv )
{
    int idx = 0;
    unsigned count = 0;
    
    for( idx = 1; idx < argc; idx++ ) {
        count += process_directory( argv[idx] );
    }
    
    return EXIT_SUCCESS;
}

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1) I got some errors while compiling this code, not too sure what are these

as3.c: In function `process_directory':
as3.c:30: error: too many arguments to function `readdir_r'
as3.c:30: warning: assignment makes integer from pointer without a cast
as3.c:38: error: too many arguments to function `readdir_r'
as3.c:38: warning: assignment makes integer from pointer without a cast
as3.c:79: error: too many arguments to function `readdir_r'
as3.c:79: warning: assignment makes integer from pointer without a cast

2) Is that possible for me to use chdir in this prog? Let's say if i remove the following line and replace with the chdir func (like chdir (entry.d_name) and chdir (".."))?
           retval = readdir_r( dir, &entry, &entryPtr );

3) what does this return >> EXIT_SUCCESS at the end of the main func what is the difference than the usual?

4) Is there any difference of using void and without void in some of these lines, what do they meant to be here?
(void)strncpy( pathName, theDir, PATH_MAX );
      (void)strncat( pathName, "/", PATH_MAX );
      (void)strncat( pathName, entry.d_name, PATH_MAX );

5) Is there any possibility for me getting a NULL when reading a directory?

Any help will be greatly appreciated:)

ASKER CERTIFIED SOLUTION

Narendra Kumar S S

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SOLUTION

Infinity08

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Infinity08

Heh, sorry for repeating you, ssnkumar :)