Bprint returns zero on success.
 [rsc] --rw-rw-r-- M 1309610 glenda sys 6523 Jan 26 23:14 sys/man/2/bio
	/n/sourcesdump/2006/0126/plan9/sys/man/2/bio:271,277 - 
	/n/sourcesdump/2006/0127/plan9/sys/man/2/bio:271,279
	  a negative value
	  .RB ( Beof )
	  is returned.
	- Otherwise, the number of bytes output is returned.
	+ Otherwise, 
	+ .I Bprint
	+ returns zero.
	  .I Bvprint
	  does the same except it takes as argument a
	  .B va_list
 [rsc] --rw-rw-r-- M 1309610 glenda sys 44583 Jan 26 23:15 sys/src/cmd/upas/ned/nedmail.c
	/n/sourcesdump/2006/0126/plan9/sys/src/cmd/upas/ned/nedmail.c:1460,1466 - 
	/n/sourcesdump/2006/0127/plan9/sys/src/cmd/upas/ned/nedmail.c:1460,1466
	  		if(interrupted)
	  			break;
	  		p[Blinelen(b)-1] = 0;
	- 		if(Bprint(&out, "%s%s\n", indent, p) <= 0)
	+ 		if(Bprint(&out, "%s%s\n", indent, p) < 0)
	  			break;
	  	}
	  	Bprint(&out, "\n");