[unix-pc.bugs] Named pipes on the UNIX PC, is there a problem with ls

lenny@icus.islp.ny.us (Lenny Tropiano) (09/26/88)

The "mknod(1M)" command can be used to create character and block
devices, as well as, FIFO's or named pipes.   mknod(1M) needs to
be run as the super-user if you are creating anything but fifo's.

Usage: mknod name c|b maj min
-or-   mknod name p

Normally when you create a named pipe, the ls(1) command signifies this
the same as it does with directories (d), character devices (c), and
block devices (b) with "p".  For some reason this doesn't work.  For
example the file /usr/spool/lp/FIFO is a named pipe, but the directory
doesn't tell us.

$ ls -l /usr/spool/lp/FIFO
-rw-------  1 lp      other         0 Sep 25 19:42 /usr/spool/lp/FIFO 
^
 Here should be a "p".

Here's a short program to test for FIFO status:

/* isfifo.c */

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>

main(argc,argv)
int argc;
char *argv[];
{
	struct	stat	statbuf;

	if (argc < 2) {
		printf("usage: %s file\n", argv[0]);
		exit(1);
	}
	if (stat(argv[1],&statbuf) < 0) {
		perror("stat()");
		exit(1);
	}
	printf("%s", argv[1]);
	if (statbuf.st_mode & S_IFIFO) 
		printf(" is ");
	else
		printf(" isn't ");
	printf("a fifo\n");
}

$ isfifo isfifo.c
isfifo.c isn't a fifo

$ isfifo /usr/spool/lp/FIFO
/usr/spool/lp/FIFO is a fifo

Why can't ls(1) do this too?  I've seen it work elsewhere.

-Lenny
---
Lenny Tropiano             ICUS Software Systems         w: +1 (516) 582-5525
lenny@icus.islp.ny.us      Telex: 154232428 ICUS         h: +1 (516) 968-8576
{talcott,boulder,hombre,pacbell,sbcs}!icus!lenny         attmail!icus!lenny
        ICUS Software Systems -- PO Box 1; Islip Terrace, NY  11752

mark@jhereg.Jhereg.MN.ORG (Mark H. Colburn) (09/27/88)

The file(1) command will also tell you whether a file is a named pipe.
For example:

	$ file /usr/spool/lp/FIFO
	/usr/spool/lp/FIFO:	fifo

I find it easier than using another program. (sorry, Lenny...)

dpb@tellab5.tellabs.CHI.IL.US (Darryl Baker) (09/27/88)

Well sports fans the reason ls on the 3B1 is not marking named pipes correctly
is that it is the BSD version of ls. It must not have been modified to handle
named pipes. The easiest way to check this is link /bin/ls and /bin/lf then type
lf. It will act as if you typed "ls -F", a totally Berkeley trait.
-- 
   __                      _      __
  /  )                    //     /  )       /
 /  / __.  __  __  __  , //     /--<  __.  /_  _  __    Darryl Baker
/__/_(_/|_/ (_/ (_/ (_/_</_    /___/_(_/|_/ <_</_/ (_   dpb@tellabs.chi.il.us
                     /					dpb@liltyke.chi.il.us
                    '

ditto@cbmvax.UUCP (Michael "Ford" Ditto) (09/27/88)

In article <1099@tellab5.tellabs.CHI.IL.US> dpb@tellab5.UUCP (Darryl Baker) writes:
>Well sports fans the reason ls on the 3B1 is not marking named pipes correctly
>is that it is the BSD version of ls. It must not have been modified to handle
>named pipes. The easiest way to check this is link /bin/ls and /bin/lf then type
>lf. It will act as if you typed "ls -F", a totally Berkeley trait.

Those are "standard" features of ls from AT&T; they were taken out for
System V for some reason.  Darryl is correct, though in pointing out that
it is a symptom of the problem... the Unix PC apparrently has the V7 ls.

Perhaps I should fix the one last bug in my own ls program and post it;
it's what I've always been using, so I never noticed the missing fifo
support.
-- 
					-=] Ford [=-

"The number of Unix installations	(In Real Life:  Mike Ditto)
has grown to 10, with more expected."	ford@kenobi.cts.com
- The Unix Programmer's Manual,		...!sdcsvax!crash!elgar!ford
  2nd Edition, June, 1972.		ditto@cbmvax.commodore.com