.de NP
.in -0.8i
@l'6.5i'
'bp
.sp 0.5i
.ps 10
.ft B
.tl 'csci-e28'lecture 4 samples'page %'
.ft R
@l'6.5i'
.ft C
.ps 8
.vs 9p
.in +0.8i
.nf
..
.ec @
.nf
.sp 0.5i
.ft B
.tl 'csci-e28'lecture 4 samples'page %'
.ft R
@l'6.5i'
.ft C
.ps 8
.vs 9p
.in +0.8i
:::::::::::::: perror_demo.c ::::::::::::::
#include	<stdio.h>
#include	<errno.h>
#include	<string.h>
#include	<fcntl.h>

/* program   perror_demo.c
 * purpose   show how errno is set by syscalls
 *           and how perror prints the associated message
 *   usage   perror_demo
 *   action  tries to open() a file for a given mode
 *           then, if error, prints errno and message
 */

int main()
{
	char	name[100];			/* filename		*/
	int	mode;				/* second arg to open	*/
	int	rv = 0;				/* program status reprt */

	printf("Open what file or dir? "); 
	fgets(name, 100, stdin);
	name[strlen(name)-1] = '\0';
	printf("   Open %s for 0,1, or 2? ", name);
	scanf("%d", &mode);
	if ( open( name, mode ) == -1 ){
		printf("Oh No!, errno %d just occurred\n", errno);
		perror( name );			/* print message	*/
		rv = 1;
	}
	else
		printf("%s opened ok\n", name );

	return rv;
}
:::::::::::::: dig ::::::::::::::
#!/bin/sh
#
# script   dig
# purpose  show how to dig deep holes in a file system
# method   mkdir s; cd s; repeat  (like on shampoo bottles)
# warning  good way to annoy system managers

	while true
	do
		mkdir s
		cd s
	done

:::::::::::::: rm1.c ::::::::::::::
#include	<stdio.h>
#include	<unistd.h>

/* example of using unlink to 'delete' a file */

int main(int ac, char *av[])
{
	int	rv = 0;
	while(--ac){
		if ( unlink( *++av ) == -1 ){
			perror(*av);
			rv = 1;
		}
		else
			printf("%s is gone\n", *av);
	}
	return rv;
}
.NP
:::::::::::::: rm2.c ::::::::::::::
#include	<stdio.h>
#include	<unistd.h>
/*
 * rm2 - interactive version of rm using unlink(2)
 */

int main()
{
	char	name[100];
	char	confirm[100];
	int	rv = 0;			/* return value from main */

	while ( printf("delete what file? "), fgets(name,100,stdin) ){
		printf("about to unlink %s, ok? ", name );
		fgets(confirm,100,stdin);
		if ( *confirm == 'y' ){
			if( unlink(name) == -1 ){
				perror(name);
				rv = 1;
			}
			else
				printf("%s is gone\n", name);
		}
	}
	return rv;
}

:::::::::::::: mv1.c ::::::::::::::
#include	<stdio.h>
#include	<errno.h>
#include	<stdlib.h>
#include	<unistd.h>

/*
 * program  mv1.c
 * purpose  show how to use link and unlink to rename a file
 * notes    checks errno to make it more adaptable
 * note     This version could be replaced by rename() but it
 *          works differently when the target exists
 */

int main(int ac, char *av[])
{

	if ( link( av[1], av[2]) != -1 )
		unlink( av[1] );

	else if ( errno == EEXIST )		/* name2 already in use */
	{
		if (unlink( av[2] ) == -1 )	/* not any more		*/
		{
			perror(av[2]);		
			exit(1);
		}
		return main(ac,av);		/* and try again	*/
	}
	return 0;
}
.NP
:::::::::::::: mv2.c ::::::::::::::
#include	<stdio.h>
#include	<limits.h>
#include	<unistd.h>
#include	<stdlib.h>
#include	<string.h>

/**
 **	mv28 version 1
 **
 **		if last arg is a dir, then move all files into there
 **		if two args and last is a file, then move first to
 **		second.  will clobber second if exists.
 **		Uses isadir .
 **
 **		problems: 1) what if an arg is a dir?
 **			  2) what about paths in source files?
 **/

void mv(char *,char *);
void mv_to_newdir(int, char **, char *);
int  isadir(char *);

int main( int ac, char *av[] )
{
	if ( ac < 3 ){
		fprintf( stderr, "too few args\n");
		exit(1);
	}

	/*
	 *	if last arg is a dir, then move args to there
 	 */
	if ( isadir( av[ac-1] ) )
		mv_to_newdir(ac-1,av,av[ac-1]);

	/*
	 *	last arg is not a dir, so must be two args only
	 */
	else if ( ac != 3 ){
		fprintf( stderr, "too many args\n");
		exit(1);
	}
	else mv(av[1], av[2]);
	return 0;
}

void mv_to_newdir( int ac, char *av[], char *newdir )
/*
 *	move av[1], av[2], ... av[ac-1] into newdir
 */
{
	char	newpath[PATH_MAX];
	int	pos ;

	for( pos = 1 ; pos<ac; pos++ ){
		if ( strlen(newdir)+strlen(av[pos])+2 <= PATH_MAX )
		{
			sprintf( newpath , "%s/%s", newdir, av[pos]);
			mv( av[pos] , newpath );
		}
	}
}

void mv( char *oldname, char *newname )
{
	if ( link(oldname, newname) == -1 || unlink(oldname) == -1 ){
		fprintf(stderr,"error mv'ing %s to %s\n", oldname, newname);
		exit(1);
	}
}
.NP
:::::::::::::: pwd28.c ::::::::::::::
#include	<stdio.h>
#include	<sys/types.h>
#include	<sys/stat.h>
#include	<dirent.h>
#include	<unistd.h>
#include	<stdlib.h>
#include	<string.h>

/**
 **	a simplified version of pwd
 **
 **	Starts in current directory and recursively
 **	   climbs up to root of filesystem, prints top part
 **	   then prints current part
 **	Uses readdir() to get info about each thing
 **/

void	get_info(char*, dev_t *, ino_t *);
void    printpathto(dev_t, ino_t);
void	inum_to_name(dev_t , ino_t , char *);

int main()
{
	ino_t	myinode ;
	dev_t	mydev   ;

	get_info(".", &mydev, &myinode);
	printpathto( mydev, myinode );		/* print path to here	*/
	putchar('\n');				/* then add newline	*/
	return 0;
}

void printpathto( dev_t this_dev, ino_t this_inode )
/*
 *	prints path leading down to an object with this dev,inode
 */
{
	ino_t	myinode , par_inode;
	dev_t	mydev,    par_dev;
	char	its_name[BUFSIZ];

	chdir( ".." );					/* up one dir	*/

	inum_to_name(this_dev,this_inode,its_name );	/* get its name	*/

	get_info(".",&mydev,&myinode);			/* print head	*/
	get_info("..",&par_dev,&par_inode);
	if ( myinode != par_inode || mydev != par_dev )
		printpathto( mydev, myinode );		/* recursively	*/
	printf("/%s", its_name );			/* now print	*/
							/* name of this	*/
}

/*
 * gets inode and dev for the specified path, uses lstat
 */
void get_info(char *path, dev_t *dp, ino_t *inp)
{
	struct stat info;

	if ( lstat(path, &info) == -1 ){
		perror(path);
		exit(2);
	}
	*inp = info.st_ino;
	*dp  = info.st_dev;
}
.NP
void inum_to_name(dev_t dev_to_find, ino_t inode_to_find , char *namebuf)
/*
 *	looks through current directory for a file with this inode
 *	number and copies its name into namebuf
 */
{
	DIR		*dir_ptr;		/* the directory */
	struct dirent	*direntp;		/* each entry	 */
	ino_t		cur_inum;
	dev_t		cur_dev;

	dir_ptr = opendir( "." );
	if ( dir_ptr == NULL ){
		fprintf(stderr, "cannot open a directory\n");
		exit(1);
	}
	/*
	 * search directory for a file with specified inum and device
	 */
	while ( ( direntp = readdir( dir_ptr ) ) != NULL ){
		get_info(direntp->d_name, &cur_dev, &cur_inum);
		if ( cur_inum == inode_to_find && cur_dev == dev_to_find )
		{
			strcpy( namebuf, direntp->d_name );
			closedir( dir_ptr );
			return ;
		}
	}
	fprintf(stderr, "error looking for inum %d\n", (int) inode_to_find);
	exit(1);
}