Re: [gentoo-dev] multiprocessing.eclass: doing parallel work in bash

[Zac Medico]

On 06/02/2012 12:54 PM, Mike Frysinger wrote:

> # @FUNCTION: redirect_alloc_fd
> # @USAGE: <var> <file> [redirection]
> # @DESCRIPTION:
> # Find a free fd and redirect the specified file via it.  Store the new
> # fd in the specified variable.  Useful for the cases where we don't care
> # about the exact fd #.
> redirect_alloc_fd() {
> 	local var=$1 file=$2 redir=${3:-"<>"}
>
> 	if [[ $(( (BASH_VERSINFO[0] << 8) + BASH_VERSINFO[1] )) -ge $(( (4 << 8) + 1 )) ]] ; then
> 		# Newer bash provides this functionality.
> 		eval "exec {${var}}${redir}'${file}'"
> 	else
> 		# Need to provide the functionality ourselves.
> 		local fd=10
> 		while :; do
> 			if [[ ! -L /dev/fd/${fd} ]] ; then
> 				eval "exec ${fd}${redir}'${file}'" && break
> 			fi
> 			[[ ${fd} -gt 1024 ]] && return 1 # sanity
> 			: $(( ++fd ))
> 		done
> 		: $(( ${var} = fd ))
> 	fi
> }

I launched up a GhostBSD livedvd to see what /dev/fd/ looks like on
FreeBSD, and it seems to contain plain character devices instead of
symlinks to character devices:

[ghostbsd@livecd ~]$ uname -a
FreeBSD livecd 9.0-RELEASE FreeBSD 9.0-RELEASE #0: Sun Jan 15 17:17:43
AST 2012
root@××××××××××××××××.org:/usr/obj/i386.i386/usr/src/sys/GHOSTBSD  i386
[ghostbsd@livecd ~]$ ls -l /dev/fd/
total 0
crw-rw-rw-  1 root  wheel    0,  19 Jun  2 20:15 0
crw-rw-rw-  1 root  wheel    0,  21 Jun  2 20:15 1
crw-rw-rw-  1 root  wheel    0,  23 Jun  2 20:15 2

-- 
Thanks,
Zac