Skunkware 5/Skunkware 5.iso/bin/dislocate

Text File | 1995-07-21 | 7KB | 341 lines

#!/usr/skunk/bin/expect --
# dislocate - allow disconnection and reconnection to a background program
# Author: Don Libes, NIST

exp_version -exit 5.1

# The following code attempts to intuit whether cat buffers by default.
# The -u flag is required on HPUX (8 and 9) and IBM AIX (3.2) systems.
if [file exists $exp_exec_library/cat-buffers] {
    set catflags "-u"
} else {
    set catflags ""
}
# If this fails, you can also force it by commenting in one of the following.
# Or, you can use the -catu flag to the script.
#set catflags ""
#set catflags "-u"

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

set pidfile "~/.dislocate"
set prefix "disc"
set timeout -1
set debug_flag 0

while {$argc} {
    set flag [lindex $argv 0]
    switch -- $flag \
    "-catu" {
        set catflags "-u"
        set argv [lrange $argv 1 end]
        incr argc -1
    } "-escape" {
        set escape [lindex $argv 1]
        set escape_printable $escape
        set argv [lrange $argv 2 end]
        incr argc -2
    } "-debug" {
        log_file [lindex $argv 1]
        set debug_flag 1
        set argv [lrange $argv 2 end]
        incr argc -2
    } default {
        break
    }
}

# These are correct from parent's point of view.
# In child, we will reset these so that they appear backwards
# thus allowing following two routines to be used by both parent and child
set  infifosuffix ".i"
set outfifosuffix ".o"

proc infifoname {pid} {
    global prefix infifosuffix

    return "/tmp/$prefix$pid$infifosuffix"
}

proc outfifoname {pid} {
    global prefix outfifosuffix

    return "/tmp/$prefix$pid$outfifosuffix"
}

proc pid_remove {pid} {
    global date proc

    say "removing $pid $proc($pid)"

    unset date($pid)
    unset proc($pid)
}

# lines in data file looks like this:
# pid#date-started#argv

# allow element lookups on empty arrays
set date(dummy) dummy;    unset date(dummy)
set proc(dummy) dummy;    unset proc(dummy)

# load pidfile into memory
proc pidfile_read {} {
    global date proc pidfile

    if [catch {open $pidfile} fp] return

    #
    # read info out of file
    #

    say "reading pidfile"
    set line 0
    while {[gets $fp buf]!=-1} {
        # while pid and date can't have # in it, proc can
        if [regexp "(\[^#]*)#(\[^#]*)#(.*)" $buf junk pid xdate xproc] {
            set date($pid) $xdate
            set proc($pid) $xproc
        } else {
            puts "warning: inconsistency in $pidfile line $line"
        }
        incr line
    }
    close $fp
    say "read $line entries"

    #
    # see if pids and fifos are still around
    #

    foreach pid [array names date] {
        if {$pid && [catch {exec /bin/kill -0 $pid}]} {
            say "$pid no longer exists, removing"
            pid_remove $pid
            continue
        }

        # pid still there, see if fifos are
        if {![file exists [infifoname $pid]] || ![file exists [outfifoname $pid]]} {
            say "$pid fifos no longer exists, removing"
            pid_remove $pid
            continue
        }
    }
}

proc pidfile_write {} {
    global pidfile date proc

    say "writing pidfile"

    set fp [open $pidfile w]
    foreach pid [array names date] {
        puts $fp "$pid#$date($pid)#$proc($pid)"
        say "wrote $pid#$date($pid)#$proc($pid)"
    }
    close $fp
}

proc fifo_pair_remove {pid} {
    global date proc prefix

    pidfile_read
    pid_remove $pid
    pidfile_write

    catch {exec rm -f [infifoname $pid] [outfifoname $pid]}
}

proc fifo_pair_create {pid argdate argv} {
    global prefix date proc

    pidfile_read
    set date($pid) $argdate
    set proc($pid) $argv
    pidfile_write

    mkfifo [infifoname $pid]
    mkfifo [outfifoname $pid]
}

proc mkfifo {f} {
    if [file exists $f] {
        say "uh, fifo already exists?"
        return
    }

    if 0==[catch {exec mkfifo $f}] return        ;# POSIX
    if 0==[catch {exec mknod $f p}] return
    # some systems put mknod in wierd places
    if 0==[catch {exec /usr/etc/mknod $f p}] return    ;# Sun
    if 0==[catch {exec /etc/mknod $f p}] return    ;# AIX, Cray
    puts "Couldn't figure out how to make a fifo - where is mknod?"
    exit
}

proc child {argdate argv} {
    global catflags infifosuffix outfifosuffix

    disconnect

    # these are backwards from the child's point of view so that
    # we can make everything else look "right"
    set  infifosuffix ".o"
    set outfifosuffix ".i"
    set pid 0

    eval spawn $argv
    set proc_spawn_id $spawn_id

    while {1} {
        say "opening [infifoname $pid] for read"
         spawn -open [open "|cat $catflags < [infifoname $pid]" "r"]
        set in $spawn_id

        say "opening [outfifoname $pid] for write"
        spawn -open [open [outfifoname $pid] w]
        set out $spawn_id

        fifo_pair_remove $pid

        say "interacting"
        interact {
            -u $proc_spawn_id eof exit
            -output $out
            -input $in
        }

        # parent has closed connection
        say "parent closed connection"
        catch {close -i $in}
        catch {close -i $out}

        # switch to using real pid
        set pid [pid]
        # put entry back
        fifo_pair_create $pid $argdate $argv
    }
}

proc say {msg} {
    global debug_flag

    if !$debug_flag return

    if [catch {puts "parent: $msg"}] {
        send_log "child: $msg\n"
    }
}

proc escape {} {
    # export process handles so that user can get at them
    global in out

    puts "\nto disconnect, enter: exit (or ^D)"
    puts "to suspend, press appropriate job control sequence"
    puts "to return to process, enter: return"
    interpreter
    puts "returning ..."
}

# interactively query user to choose process, return pid
proc choose {} {
    global index date

    while 1 {
        send_user "enter # or pid: "
        expect_user -re "(.*)\n" {set buf $expect_out(1,string)}
        if [info exists index($buf)] {
            set pid $index($buf)
        } elseif [info exists date($buf)] {
            set pid $buf
        } else {
            puts "no such # or pid"
            continue
        }
        return $pid
    }
}

if {$argc} {
    # initial creation occurs before fork because if we do it after
    # then either the child or the parent may have to spin retrying
    # the fifo open.  Unfortunately, we cannot know the pid ahead of
    # time so use "0".  This will be set to the real pid when the
    # parent does its initial disconnect.  There is no collision
    # problem because the fifos are deleted immediately anyway.

    set datearg [exec date]
    fifo_pair_create 0 $datearg $argv

    set pid [fork]
    say "after fork, pid = $pid"
    if $pid==0 {
        child $datearg $argv
    }
    # parent thinks of child as pid==0 for reason given earlier
    set pid 0
}

say "examining pid"

if ![info exists pid] {
    global fifos date proc

    say "pid does not exist"

    pidfile_read

    set count 0
    foreach pid [array names date] {
        incr count
    }

    if $count==0 {
        puts "no connectable processes"
        exit
    } elseif $count==1 {
        puts "one connectable process: $proc($pid)"
        puts "pid $pid, started $date($pid)"
        send_user "connect? \[y] "
        expect_user -re "(.*)\n" {set buf $expect_out(1,string)}
        if {$buf!="y" && $buf!=""} exit
    } else {
        puts "connectable processes:"
        set count 1
        puts " #   pid      date started      process"
        foreach pid [array names date] {
            puts [format "%2d %6d  %.19s  %s" \
                $count $pid $date($pid) $proc($pid)]
            set index($count) $pid
            incr count
        }
        set pid [choose]
    }
}

say "opening [outfifoname $pid] for write"
spawn -noecho -open [open [outfifoname $pid] w]
set out $spawn_id

say "opening [infifoname $pid] for read"
spawn -noecho -open [open "|cat $catflags < [infifoname $pid]" "r"]
set in $spawn_id

puts "Escape sequence is $escape_printable"

proc prompt1 {} {
    global argv0

    return "$argv0[history nextid]> "
}

interact {
    -reset $escape escape
    -output $out
    -input $in
}