Term::ReadKey, non-blocking read in raw mode: Detect EOF? - perl

Question

When I pipe stuff into my program, it does not seem to get any character like 0x4 to indicate EOF.
$ echo "abc" | map 'cat'
saw a: \x61
saw b: \x62
saw c: \x63
saw
: \x0A
zzzbc
^C
I have to press Ctrl+C to quit, but I'm not really sure what the Ctrl+C is acting on. It's probably having the shell send a SIGINT to the pipeline? I don't know how pipelines work on that level.
Here is my program map:
#!/usr/bin/env perl
use strict;
use warnings;
use IO::Pty::Easy;
use Term::ReadKey;
use Encode;
$#ARGV % 2 and die "Odd number of args required.\n";
if ($#ARGV == -1) {
warn ("No args provided. A command must be specified.\n");
exit 1;
}
# be sure to enter the command as a string
my %mapping = #ARGV[-#ARGV..-2];
my $interactive = -t STDIN;
# my %mapping = #ARGV;
# my #mapkeys = keys %mapping;
# warn #mapkeys;
if ($interactive) {
print "Spawning command in pty: #ARGV\n"
# print "\nContinue? (y/n)";
# my $y_n;
# while (($y_n = <STDIN>) !~ /^(y|n)$/) {
# print '(y/n)';
# }
# exit if $y_n eq "n\n";
}
my $pty = IO::Pty::Easy->new();
my $spawnret = $pty->spawn("#ARGV")."\n";
print STDERR "Spawning has failed: #ARGV\n" if !$spawnret;
ReadMode 4;
END {
ReadMode 0; # Reset tty mode before exiting
}
my $i = undef;
my $j = 0;
{
local $| = 1;
while (1) {
myread();
# responsive to key input, and pty output may be behind by 50ms
my $key = ReadKey(0.05);
# last if !defined($key) || !$key;
if (defined($key)) {
my $code = ord($key); # this byte is...
if ($interactive and $code == 4) {
# User types Ctrl+D
print STDERR "Saw ^D from term, embarking on filicide with TERM signal\n";
$pty->kill("TERM", 0); # blocks till death of child
myread();
$pty->close();
last;
}
printf("saw %s: \\x%02X\n", $key, $code);
# echo translated input to pty
if ($key eq "a") {
$pty->write("zzz"); # print 'Saw "a", wrote "zzz" to pty';
} else {
$pty->write($key); # print "Wrote to pty: $key";
}
}
}
}
sub myread {
# read out pty's activity to echo to stdout
my $from_pty = $pty->read(0);
if (defined($from_pty)) {
if ($from_pty) {
# print "read from pty -->$from_pty<--\n";
print $from_pty;
} else {
if ($from_pty eq '') {
# empty means EOF means pty has exited, so I exit because my fate is sealed
print STDERR "Got back from pty EOF, quitting\n" if $interactive;
$pty->close();
last;
}
}
}
}
That would explain why it produced "zzzbc".
Now my question is how can I get map to be able to know about echo "abc" having reached the end of input? cf. echo "abc" | cat completes on its own. ReadKey does not seem to provide API for determining this situation.
Similarly I am not sure how to do the same to pass along the EOF to the child in the pty. I am thinking this might cause issues when a command is to write to a file or something, because EOF vs sending a kill signal is the difference between writing the file correctly and not exiting cleanly.

Answer 1

Try reading from STDIN and not that $pty object. The pipe you create via the shell passes the data to your STDIN file descriptor 0, which in perl is your handle .
The $pty, I assume that's your terminal. That's why the script just hangs (I guess).