static int decode()
{
	extern int errno;
	struct passwd *pw;
	register int n;
	register char ch, *p;
	int mode, n1;
	char buf[MAXPATHLEN];

	/* search for header line */
	do{
		if(!fgets(buf,sizeof(buf),stdin))
		{
			(void)fprintf(stderr,"uudecode: %s: no \"begin\" line\n", filename);
			return(1);
		}
	}while(strncmp(buf,"begin ",6));

	(void)sscanf(buf,"begin %o %s",&mode,buf);
	/* handle ~user/file format */
	if(buf[0]=='~')
	{
		if(!(p=index(buf,'/')))
		{
		  (void)fprintf(stderr, "uudecode: %s: illegal ~user.\n",filename);
			return(1);
		}
		*p++=NULL;
		if(!(pw=getpwnam(buf+1)))
		{
			(void)fprintf(stderr,"uudecode: %s: no user %s.\n",filename,buf);
			return(1);
		}
		n=strlen(pw->pw_dir);
		n1=strlen(p);
		if(n+n1+2>MAXPATHLEN)
		{
			(void)fprintf(stderr, "uudecode: %s: path too long.\n",filename);
			return(1);
		}
		bcopy(p,buf+n+1,n1+1);
		bcopy(pw->pw_dir,buf,n);
		buf[n]='/';
	}
	/* create output file, set mode */
	if(!freopen(buf,"w",stdout)||fchmod(fileno(stdout),mode&0666))
	{
		(void)fprintf(stderr,"uudecode: %s: %s: %s\n", buf,filename,strerror(errno));
		return(1);
	}
	// for each input line
	for(;;)
	{
		if(!fgets(p=buf,sizeof(buf),stdin))
		{
			(void)fprintf(stderr,"uudecode: %s: short file.\n",filename);
			return(1);
		}
#define	DEC(c)	(((c) - ' ') & 077)		/* single character decode */
//  '`n' is used to avoid writing out all the characters at the end of the file.
		if((n=DEC(*p))<=0)break;
		for(++p;n>0;p+=4,n-=3)
			if(n>=3)
			{
				ch=DEC(p[0])<<2|DEC(p[1])>>4;
				putchar(ch);
				ch=DEC(p[1])<<4|DEC(p[2])>>2;
				putchar(ch);
				ch=DEC(p[2])<<6|DEC(p[3]);
				putchar(ch);
			}
			else
			{
			  if(n>=1)
				{
					ch=DEC(p[0])<<2|DEC(p[1])>>4;
					putchar(ch);
				}
				if(n>=2)
				{
					ch=DEC(p[1])<<4|DEC(p[2])>>2;
					putchar(ch);
				}
				if(n>=3)
				{
					ch=DEC(p[2])<<6|DEC(p[3]);
					putchar(ch);
				}
			}
	}
	if(!fgets(buf,sizeof(buf),stdin)||strcmp(buf,"end\n"))
	{
		(void)fprintf(stderr, "uudecode: %s: no \"end\" line.\n",filename);
		return(1);
	}
	return(0);
}

static void
usage()
{
	(void)fprintf(stderr, "usage: uudecode [file ...]\n");
	exit(1);
}