Bug: read -n strips leading and trailing whitespace

[glyh]

Script a:

#!/usr/bin/env ysh

var block_size = 4
var EOF=']]]'
while (true) {
  read -n $block_size chunk
  write -n $chunk$EOF
}

script b:

#!/usr/bin/env bash

EOF=']]]'
while true
do
  read -n4 chunk
  echo -n $chunk$EOF
  sleep 1
done

test:

$ echo 'I am a pretty long string' |  ./a
I am]]]a p]]]rett]]]y lo]]]ng s]]]trin]]]g]]]    read -n $block_size chunk
    ^~~~
./a:6: errexit PID 501165: command.Simple failed with status 1
$ echo 'I am a pretty long string' |  ./b
I am]]]a p]]]rett]]]y lo]]]ng s]]]trin]]]g]]]]]]]]]]]]]]]]]]]] (omitted, bash keeps hanging forever even if the stdin to read is closed) 

[glyh]

Was bitten by this when testing channels.

[andychu]

Hmm actually this is an Oils bug only? What's wrong with bash?

andy@andy-VirtualBox:~/git/oilshell/oil$ bash -c 'echo " a b" |(read -n 4; echo "$REPLY")'
 a b
andy@andy-VirtualBox:~/git/oilshell/oil$ bin/osh -c 'echo " a b" |(read -n 4; echo "$REPLY")'
a b

Great find, thank you

I believe it might be related to stripping leading and trailing whitespace

[andychu]

andy@andy-VirtualBox:~/git/oilshell/oil$ bash -c 'echo "  a b  " |(read -n 7; echo "[$REPLY]")'
[  a b  ]
andy@andy-VirtualBox:~/git/oilshell/oil$ bin/osh -c 'echo "  a b  " |(read -n 7; echo "[$REPLY]")'
[a b]

[andychu]

OK I wrote some failing spec tests

I think there are multiple things going on here, let me start a Zulip thread