Finding headless shells

headless.pl

#!/usr/bin/perl -an

# One-liner version:
# lsof -d txt,0,1,2 | perl -anE'push@g,$F[1]if$F[4]eq"CHR"and$F[8]=~/^.dev.[pt]t[sy]/;$t{$F[1]}=$_ if$F[3]eq"txt"and$F[8]=~/^.(usr.)?bin.((b|d)?a|z|k|c|tc)*sh/;END{delete$t{$_}for@g;say values%t}'

# store the PID of processes that use a PTY/TTY for STDIN, STDOUT, or STDERR
push @g, $F[1] if $F[4] eq "CHR" and $F[8]=~/^.dev.[pt]t[sy]/;

# Store the whole line if the txt file descriptor is a shell
$t{$F[1]}=$_ if $F[3] eq "txt" and $F[8]=~/^.(usr.)?bin.((b|d)?a|z|k|c|tc)*sh/;

END {
  # clear out the PIDs that use a pty/tty
  delete $t{$_} for @g;
  # and print what's left
  say values %t;
}