How not to mess terminal up after sys.stdin.read() and subprocess invoking vim?

Question

I want to create interactive mode code like git rebase -i HEAD~6 but for PIPE editing, stdin redirection. another example is vipe of moreutils.

To do that, I learn this code below.

# Source: https://stackoverflow.com/a/39989442/20307768
import sys, tempfile, os
from subprocess import call

EDITOR = os.environ.get('EDITOR', 'vim')  # that easy!

initial_message = b'something'  # if you want to set up the file somehow

with tempfile.NamedTemporaryFile(suffix=".tmp") as tf: 
  tf.write(initial_message)
  tf.flush()
  call([EDITOR, tf.name])

To get PIPE and edit it, I added two lines.

text = sys.stdin.read()
initial_message = text.encode()

The problematic full code is below.

import sys, tempfile, os
from subprocess import call

EDITOR = os.environ.get('EDITOR', 'vim')

text = sys.stdin.read()
initial_message = text.encode()

with tempfile.NamedTemporaryFile(suffix=".tmp") as tf: 
    tf.write(initial_message)
    tf.flush()
    call([EDITOR, tf.name])

After running the second code with echo "some words" | python the_code.py in the shell and exiting vim:q!, the terminal is messed up. (reset in the shell command will fix it.)

Without reset, I can type in a shell of macOS, but the prompt is in a weird place.
I can’t even type in a shell of Linux.

I typed set -x, already.

[rockyos@localhost python-vipe]$ echo "asdfasd" | python vipe.py
+ python vipe.py
+ echo asdfasd
Vim: Warning: Input is not from a terminal
++ printf '33]0;%s@%s:%s07' rockyos localhost '~/TODO/python-vipe'
                                                                            ++ history -a
                                                                                         ++ history -c
                                                                                                      ++ history -r
                                                                                                                   [transmission@localhost python-vipe]$

I just want to return normal terminal after running the second full code.
Also, why is this happening?

I tried os.system('stty sane; clear;') and os.system('reset') at the end of the code.(https://stackoverflow.com/a/17452756/20307768) os.system('reset') gave me what I wanted. But the message is annoying. I mean I can do os.system('clear') again, but that is not what normal other program does.

Erase set to delete. 
Kill set to control-U (^U). 
Interrupt set to control-C (^C).

Asked By: Constantin Hong

||

Source

Answer 1

I want to create interactive mode code like git rebase -i HEAD~6 but for PIPE editing, stdin redirection. another example is vipe of moreutils.

vipe is an open-source tool, and the source code is less than 100 lines long, so let’s take a moment to look at how it does this. It can’t rely on stdin or stdout to be a terminal, because normally it’s used in the middle of a series of pipes.

Here’s how they solved that, in Perl. First, they close STDIN, or file descriptor 0. Then, they open /dev/tty in read mode at descriptor 0. They also do the same thing for STDOUT, but we don’t need that.

close STDIN;
open(STDIN, "</dev/tty") || die "reopen stdin: $!";
open(OUT, ">&STDOUT") || die "save stdout: $!";
close STDOUT;
open(STDOUT, ">/dev/tty") || die "reopen stdout: $!";

So, how can we do the same thing in Python?

Open /dev/tty in read mode.
That might not have been opened at descriptor 0, so copy it to descriptor 0.
Close the old FD.

Code:

import sys, tempfile, os
from subprocess import check_call

EDITOR = os.environ.get('EDITOR', 'vim')

text = sys.stdin.read()
initial_message = text.encode()

with tempfile.NamedTemporaryFile(suffix=".tmp") as tf: 
    tf.write(initial_message)
    tf.flush()

    stdin_fd = os.open('/dev/tty', os.O_RDONLY)
    os.dup2(stdin_fd, 0)
    os.close(stdin_fd)

    check_call([EDITOR, tf.name])

    print(open(tf.name).read())

This was tested on OSX 13.3.1.

Answered By: Nick ODell

How not to mess terminal up after sys.stdin.read() and subprocess invoking vim?

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