RE: GNU enhancement -- $(xargs cmd, list)

[Howard Chu]

I would omit the XARGS LEN. Presumably the local platform's xargs command is
already properly configured for the native system's line length limitations.

  -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc

> -----Original Message-----
> From: address@hidden [mailto:address@hidden Behalf Of
> Reid Madsen
> Sent: Monday, November 06, 2000 5:42 PM
> To: address@hidden
> Cc: address@hidden; address@hidden
> Subject: Re: GNU enhancement -- $(xargs cmd, list)
>
>
>
>  > Date: 6 Nov 2000 16:56:30 -0600
>  > From: Reid Madsen <address@hidden>
>  >
>  > I also thought about using the _POSIX_ARG_MAX and ARG_MAX
> symbols to determine
>  > when the xargs approach was really needed.  If the command
> line is within
>  > limits, then
>  >
>  >         $(xargs cmd, list)
>  >
>  > would expand to:
>  >
>  >         cmd list
>  >
>  > Do you believe this is doable/portable?
>  >
>  > Reid
>  >
>  >
>  > FYI, a quick perusal of our systems shows:
>  >
>  >         POSIX_ARG_MAX   ARG_MAX
>  >         -------------   -------
>  > Solaris         4096    1MB
>  > HP              4096    2MB
>  > AIX             4096    24576   Pathetic!
>  > OSF             4096    38912   Pathetic!
>  > NT              4096    14500   Pathetic ** 2 !
>  >
>  > Gotta love those 2-4 byte per arg limits on AIX, OSF, and NT.
>
> After experimenting with this on Solaris for about 3 hours, I've
> come to the
> conclusion that this is way to complicated.  The 'exec' man page
> states that
> the error E2BIG is returned when the sum of the command length
> and environment
> length exceeds ARG_MAX.  So, armed with that information I when out and
> created a Makefile with enough big arguments to push it right up
> to the edge.
> Adding a single character would case make to fail with:
>
>       make: execvp: num_args: Arg list too long
>
> However the 'edge' was nowhere close to the size of the command line +
> environment.  It's off by about 100K.  Yuck!
>
> So, instead, I've decided that in addtion to the $(XARGS) variable that
> GNUmake should also define a $(XARGS_LEN) variable.  Which will be used to
> measure the length of the command line.  When less the
> $(XARGS_LEN), then a
> normal command is launched, otherwise xargs is launched as"
>
>       xargs -s $(XARGS_LEN) cmd << tmpfile
>
> In our build process, based on IMAKE, we can set XARGS_LEN
> differently for the
> different platforms we build on.  IMO, this is probably the most flexible.
>
> If you have a better idea, I'd be glad to hear it.
>
> Reid
>
> --
> Reid Madsen                             address@hidden
>
> Senior Member, Tech. Staff              (972) 536-3261 (Desk)
> I2 Technologies                         (214) 850-9613 (Cellular)
> --
> Making incrementally (without 'clean') since May 18, 2000.
> Long live incremental make!
>
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