Mini Shell

#!/usr/bin/sh
# -*- tcl -*-
# The next line is executed by /bin/sh, but not tcl \
exec tclsh "$0" ${1+"$@"}

package require Expect


# share an xterm with other users
# See xkibitz(1) man page for complete info.
# Compare with kibitz.
# Author: Don Libes, NIST
# Version: 1.2

proc help {} {
    puts "Commands          Meaning"
    puts "--------          -------"
    puts "return            return to program"        
    puts "=                 list"
    puts "+ <display>       add"
    puts "- <tag>           drop"
    puts "where <display> is an X display name such as nist.gov or nist.gov:0.0"
    puts "and <tag> is a tag from the = command."
    puts "+ and - require whitespace before argument."
    puts {return command must be spelled out ("r", "e", "t", ...).}
}

proc prompt1 {} {
    return "xkibitz> "
}

proc h {} help
proc ? {} help

# disable history processing - there seems to be some incestuous relationship
# between history and unknown in Tcl 8.0
proc history {args} {}
proc unknown {args} {
    puts "$args: invalid command"
    help
}

set tag2pid(0)			[pid]
set pid2tty([pid])		"/dev/tty"
if {[info exists env(DISPLAY)]} {
    set pid2display([pid])	$env(DISPLAY)
} else {
    set pid2display([pid])	""
}

# small int allowing user to more easily identify display
# maxtag always points at highest in use
set maxtag 0

proc + {display} {
    global ids pid2display pid2tag tag2pid maxtag pid2sid
    global pid2tty env

    if {![string match *:* $display]} {
	append display :0.0
    }

    if {![info exists env(XKIBITZ_XTERM_ARGS)]} {
	set env(XKIBITZ_XTERM_ARGS) ""
    }

    set dummy1 [open /dev/null]
    set dummy2 [open /dev/null]
    spawn -pty -noecho
    close $dummy1
    close $dummy2

    stty raw -echo < $spawn_out(slave,name)
    # Linux needs additional stty, sounds like a bug in its stty to me.
    # raw should imply this stuff, no?
    stty -icrnl -icanon < $spawn_out(slave,name)

    regexp ".*(.)(.)" $spawn_out(slave,name) dummy c1 c2
    if {[string compare $c1 "/"] == 0} {
	# On Pyramid and AIX, ttynames such as /dev/pts/1
	# requre suffix to be padded with a 0
	set c1 0
    }

    set pid [eval exec xterm \
	    -display $display \
	    -geometry [stty columns]x[stty rows] \
	    -S$c1$c2$spawn_out(slave,fd) \
	    $env(XKIBITZ_XTERM_ARGS) &]
    close -slave

    # xterm first sends back window id, discard
    log_user 0
    expect {
	eof {wait;return}
	\n
    }
    log_user 1

    lappend ids $spawn_id
    set pid2display($pid) $display
    incr maxtag
    set tag2pid($maxtag) $pid
    set pid2tag($pid) $maxtag
    set pid2sid($pid) $spawn_id
    set pid2tty($pid) $spawn_out(slave,name)
    return
}

proc = {} {
    global pid2display tag2pid pid2tty

    puts "Tag  Size Display"
    foreach tag [lsort -integer [array names tag2pid]] {
	set pid $tag2pid($tag)
	set tty $pid2tty($pid)
	
	puts [format "%3d [stty columns < $tty]x[stty rows < $tty] $pid2display($pid)" $tag]
    }
}

proc - {tag} {
    global tag2pid pid2tag pid2display maxtag ids pid2sid
    global pid2tty

    if {![info exists tag2pid($tag)]} {
	puts "no such tag"
	return
    }
    if {$tag == 0} {
	puts "cannot drop self"
	return
    }

    set pid $tag2pid($tag)

    # close and remove spawn_id from list
    set spawn_id $pid2sid($pid)
    set index [lsearch $ids $spawn_id]
    set ids [lreplace $ids $index $index]

    exec kill -9 $pid
    close
    wait

    unset tag2pid($tag)
    unset pid2tag($pid)
    unset pid2display($pid)
    unset pid2sid($pid)
    unset pid2tty($pid)

    # lower maxtag if possible
    while {![info exists tag2pid($maxtag)]} {
	incr maxtag -1
    }
}

rename exit exitReal

proc exit {} {
    global pid2display

    unset pid2display([pid])	;# avoid killing self

    foreach pid [array names pid2display] {
	catch {exec kill -9 $pid}
    }
    exitReal
}

trap exit HUP

trap {
    set r [stty rows]
    set c [stty columns]
    stty rows $r columns $c < $app_tty
    foreach pid [array names pid2tty] {
	if {$pid == [pid]} continue
	stty rows $r columns $c < $pid2tty($pid)
    }
} WINCH

set escape \035		;# control-right-bracket
set escape_printable "^\]"

while {[llength $argv]>0} {
    set flag [lindex $argv 0]
    switch -- $flag \
	    "-escape" {
	set escape [lindex $argv 1]
	set escape_printable $escape
	set argv [lrange $argv 2 end]
    } "-display" {
	+ [lindex $argv 1]
	set argv [lrange $argv 2 end]
    } default {
	break
    }
}

if {[llength $argv]>0} {
    eval spawn -noecho $argv
} else {
    spawn -noecho $env(SHELL)
}
set prog $spawn_id
set app_tty $spawn_out(slave,name)

puts "Escape sequence is $escape_printable"

interact {
    -input $user_spawn_id -reset $escape {
	puts "\nfor help enter: ? or h or help"
	interpreter -eof exit
    } -output $prog
    -input ids -output $prog
    -input $prog eof exit -output $user_spawn_id -output ids
}