UNIX 文件系统基本操作

dir = opendir( "some/path/name" )
entry = readdir( dir )
while entry is not NULL:
    do_something_with( entry )
    entry = readdir( dir )
closedir( dir )

#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 ) {
            /* stat() succeeded, let's party */
            count++;
            
            if( S_ISDIR( entryInfo.st_mode ) ) {            
/* directory */
                printf( "processing %s//n", pathName );
                count += process_directory( pathName );
            } else if( S_ISREG( entryInfo.st_mode ) ) { 
/* regular file */
                printf( "/t%s has %lld bytes/n",
                    pathName, (long long)entryInfo.st_size );
            } 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;
}