ls2.c

unix linux 编程实践源代码

/* ls2.c
 *	purpose  list contents of directory or directories
 *	action   if no args, use .  else list files in args
 *	note     uses stat and pwd.h and grp.h 
 *	BUG: try ls2 /tmp  
 */
#include	<stdio.h>
#include	<sys/types.h>
#include	<dirent.h>
#include	<sys/stat.h>

void do_ls(char[]);
void dostat(char *);
void show_file_info( char *, struct stat *);
void mode_to_letters( int , char [] );
char *uid_to_name( uid_t );
char *gid_to_name( gid_t );

main(int ac, char *av[])
{
	if ( ac == 1 )
		do_ls( "." );
	else
		while ( --ac ){
			printf("%s:\n", *++av );
			do_ls( *av );
		}
}

void do_ls( char dirname[] )
/*
 *	list files in directory called dirname
 */
{
	DIR		*dir_ptr;		/* the directory */
	struct dirent	*direntp;		/* each entry	 */

	if ( ( dir_ptr = opendir( dirname ) ) == NULL )
		fprintf(stderr,"ls1: cannot open %s\n", dirname);
	else
	{
		while ( ( direntp = readdir( dir_ptr ) ) != NULL )
			dostat( direntp->d_name );
		closedir(dir_ptr);
	}
}

void dostat( char *filename )
{
	struct stat info;

	if ( stat(filename, &info) == -1 )		/* cannot stat	 */
		perror( filename );			/* say why	 */
	else					/* else show info	 */
		show_file_info( filename, &info );
}

void show_file_info( char *filename, struct stat *info_p )
/*
 * display the info about 'filename'.  The info is stored in struct at *info_p
 */
{
	char	*uid_to_name(), *ctime(), *gid_to_name(), *filemode();
	void	mode_to_letters();
        char    modestr[11];

	mode_to_letters( info_p->st_mode, modestr );

	printf( "%s"    , modestr );
	printf( "%4d "  , (int) info_p->st_nlink);	
	printf( "%-8s " , uid_to_name(info_p->st_uid) );
	printf( "%-8s " , gid_to_name(info_p->st_gid) );
	printf( "%8ld " , (long)info_p->st_size);
	printf( "%.12s ", 4+ctime(&info_p->st_mtime));
	printf( "%s\n"  , filename );

}

/*
 * utility functions
 */

/*
 * This function takes a mode value and a char array
 * and puts into the char array the file type and the 
 * nine letters that correspond to the bits in mode.
 * NOTE: It does not code setuid, setgid, and sticky
 * codes
 */
void mode_to_letters( int mode, char str[] )
{
    strcpy( str, "----------" );           /* default=no perms */

    if ( S_ISDIR(mode) )  str[0] = 'd';    /* directory?       */
    if ( S_ISCHR(mode) )  str[0] = 'c';    /* char devices     */
    if ( S_ISBLK(mode) )  str[0] = 'b';    /* block device     */

    if ( mode & S_IRUSR ) str[1] = 'r';    /* 3 bits for user  */
    if ( mode & S_IWUSR ) str[2] = 'w';
    if ( mode & S_IXUSR ) str[3] = 'x';

    if ( mode & S_IRGRP ) str[4] = 'r';    /* 3 bits for group */
    if ( mode & S_IWGRP ) str[5] = 'w';
    if ( mode & S_IXGRP ) str[6] = 'x';

    if ( mode & S_IROTH ) str[7] = 'r';    /* 3 bits for other */
    if ( mode & S_IWOTH ) str[8] = 'w';
    if ( mode & S_IXOTH ) str[9] = 'x';
}

#include	<pwd.h>

char *uid_to_name( uid_t uid )
/* 
 *	returns pointer to username associated with uid, uses getpw()
 */	
{
	struct	passwd *getpwuid(), *pw_ptr;
	static  char numstr[10];

	if ( ( pw_ptr = getpwuid( uid ) ) == NULL ){
		sprintf(numstr,"%d", uid);
		return numstr;
	}
	else
		return pw_ptr->pw_name ;
}

#include	<grp.h>

char *gid_to_name( gid_t gid )
/*
 *	returns pointer to group number gid. used getgrgid(3)
 */
{
	struct group *getgrgid(), *grp_ptr;
	static  char numstr[10];

	if ( ( grp_ptr = getgrgid(gid) ) == NULL ){
		sprintf(numstr,"%d", gid);
		return numstr;
	}
	else
		return grp_ptr->gr_name;
}