How can I convert terminal output?

Question

I want to convert all output to the terminal that a certain command generates, using some filter program. How can I achieve this?

The immediate answer might be, “Use a pipeline”. However, too many Unix tools these days deviate from the original Unix approach with its stress on composability by peeking at the context they are running in and then behaving differently depending on whether they output to a terminal or something else and, in the former case, what the capabilities of the terminal are. I want the command to act as if it was outputting to the original terminal, with its capabilities, and just convert its terminal output in addition.

Answer 1

This is how I've been doing it. I'm not sure exactly what you mean by filter, but Command 1 output: of the echo gives you the means to work with the log file.

#!/bin/bash
set -x
my_command() {
    command1_output=$(command1)
    echo "Command 1 output: $command1_output"
# Add more commands as needed

}
my_command >> my_logging_file 2>&1

Sometimes set -x is too much info. You can run tail -f my_logging_file from another terminal and watch it in real-time.

Update for comment:
Avoid the log and initiate, piped to tail, to observe immediately.

#!/bin/bash
set -x
my_command() {
    command1_output=$(command1)
    echo "Command 1 output: $command1_output"
# Add more commands as needed

}
my_command 2>&1 | tail -f /dev/stdin

Function my_command is executed, and it's stdout and stderr are piped to tail -f /dev/stdin.

---

Whereas script logs stdout & stderr, it's intended to "record" the entire session and then "played" back. You can use:

script my_session.log
# Your commands here
exit 0

Then, use scriptreplay my_session.log to watch the session.

---

The expect command is a scripting language for automating interactive programs. (i.e. commands that require user input.)
For example:

#!/usr/bin/expect
spawn my_command
expect "Input:"  # Replace with expected prompt
send "input_value\r"
expect eof

This automates interactions with my_command by waiting for the specific prompt, then sending the chosen input.