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From:	Bengt Kleberg <bengt@softwell.se>
Message-Id: <200003061105.MAA22737@trillian.softwell.se>
To:	sam-fans@hawkwind.utcs.toronto.edu, wilyfans@jli.com
Subject: Re: ssam, again
Date:	Mon, 6 Mar 2000 06:06:49 -0500


Thanks to suggestion and code by "James A. Robinson" <jim.robinson@stanford.edu>
I have managed to cut disk usage in 1/2, using a fifo instead of a tmp file.

I now think it is good enough to ship with sam-9libs. Any one aginst?
(it is still not a stream editor, and would not work if /tmp is 50 MB and
the file to edit is 50 MB, too)

script follows:
#! /usr/local/plan9/bin/rc

cmd_name = $0
fn usage {
	echo Usage: $cmd_name [-n] [-e script ] [-f sfile ] [ script ] [--] [ file ] ...
}

# directory for saving all text to be edited
# use /tmp or TMPDIR if set
tmp_dir=/tmp
if (! ~ $TMPDIR ()) {
	tmp_dir=$TMPDIR
}

# file for saving all text to be edited
tmp_file = $tmp_dir ^ /ssam.$pid.XXXXXXXX
# if OpenBSD mktemp exist, use it
if (test -x /usr/bin/mktemp) {
	tmp_file = `{/usr/bin/mktemp $tmp_file}
	# there is no change-file-into-pipe cmd, so remove it before mkfifo
	# this allows for a denial-of-service attack, but mkfifo -m protect against disclosure
	rm $tmp_file
}
mkfifo -m 0700 $tmp_file
if (! ~ $status 0) {
	echo mkfifo failed, someone is deliberatly "stealing" your filename
	echo this indicates an attempt to read the text you want to edit
	exit 4
}

# clean up on signals
fn sighup {
	rm $tmp_file
	exit 3
}
fn sigint {
	rm $tmp_file
	exit 3
}
fn sigquit {
	rm $tmp_file
	exit 3
}

# default values for variables
printall = 1
edit_script = ()
edit_type = ()

# parse command line arguments
while ({~ $1 -*} && {! ~ $1 --}) {
	switch ($1) {
	case -n
		printall = 0
		shift
	case -e
		shift
		edit_script = ($edit_script $1)
		edit_type = ($edit_type e)
		shift
	case -f
		shift
		if (test -f $1) {
			edit_script = ($edit_script $1)
			edit_type = ($edit_type f)
			shift
		} else {
			echo $0: No such sfile: $1
			exit 2
		}
	case *
		usage
		exit 1
	}
}

# anything left that is not a file is a (single) edit script
if (! test -f $1) {
		edit_script = ($edit_script $1)
		edit_type = ($edit_type e)
		shift
}

# send edit scripts to sam and contents of edit script files
# then print contents, unless -n argument
# quit (twice since file has probably not been saved)
i = 1
max = `{expr $#edit_script + 1}
{
echo r $tmp_file
while (! ~ $i $max) {
	switch ($edit_type($i)) {
	case e
		echo $edit_script($i)
	case f
		cat $edit_script($i)
	}
	i = `{expr $i + 1}
}
if (~ $printall 1) {
	echo '1,$ p'
}
echo q
echo q
} | sam -d >[2] /dev/null &
#}
sam_pid =  $apid

# anything left is file(s) to be edited, otherwise use stdin
if (~ $#* 0) {
	cat >> $tmp_file
} else {
	cat $* >> $tmp_file
}

wait $sam_pid
rm $tmp_file
exit 0