stream_log_exec.sh

#!/bin/bash

# This script doesn't work with apt-get update (even with -q). Kill -0 exits immediately.

print_empty_lines() {
  for x in $(seq "$1"); do
    tput el
    echo
  done
}

loading="/"

rotate_loading() {
  case "$loading" in
    "|") loading="/" ;;
    "/") loading="-" ;;
    "-") loading="\\" ;;
    "\\") loading="|" ;;
  esac
}

# stream_log_exec () {
DISPLAY_LINES=10
ERR_DISPLAY_LINES=20
COLOR='\033[0;34m'
RESET='\033[0m'

logfile=$(mktemp --suffix .log)

echo ">>> running: $*" >&2

echo -en "\033[6n"; IFS=';' read -sdR -a pos; init_row="${pos[0]#*[}"; init_row=$((init_row-1))

lines=$(tput lines)
diff_lines=$((lines-init_row))
if [[ $diff_lines -le "$DISPLAY_LINES" ]]; then
  init_row=$((lines - DISPLAY_LINES - 1))

  if [[ $init_row -lt 0 ]]; then
    echo "error: init_row<0 ($init_row)" >&2
    exit 1
  fi
fi

print_empty_lines "$DISPLAY_LINES"

tput el1
tput cup "$init_row" 0

cleanup_pid () {
  tput cnorm
  if kill -0 "$1" &>/dev/null; then
    kill "$1"
  fi
  if kill -0 "$1" &>/dev/null; then
    echo "Couldn't kill $1 - sending SIGKILL (logfile: $logfile)" >&2
    kill -9 "$1"
  fi
}

goto_row () {
  tput el
  tput cup "${1:-$init_row}" 0
}

tail_stream () {
  goto_row "$init_row"
  cols=$(tput cols)
  echo -ne "$COLOR"

  sed_prefix=">> "
  sed_prefix_len="${#sed_prefix}"
  
  truncate=${1:-$DISPLAY_LINES}
  truncate=$((truncate-1))  # because of loading indicator below
  
  tail -n "$truncate" "$logfile" | fold "-w$((cols-sed_prefix_len))" | tail -n "$truncate" | sed -E 's/^/>> /g' | while read -r line; do
    tput el
    echo "$line"
  done
  
  echo "$loading"
  rotate_loading
  
  echo -ne "$RESET"
}

# Function to handle command execution and dynamic output
run_command() (
  # Execute the command and pipe the output to a temporary file
  "$@" > "$logfile" 2>&1 &

  # Get the process ID of the last background command
  local cmd_pid=$!

  tput civis
  trap "cleanup_pid '$cmd_pid'" EXIT

  # echo -ne "$COLOR"

  tail_stream
  # Continuously display the last N lines of the output
  while kill -0 $cmd_pid 2>/dev/null; do
    tail_stream
    sleep 0.1
  done
  tail_stream

  num_output_lines=$(<"$logfile" wc -l)

  if [[ "$num_output_lines" -eq 0 ]]; then
    echo ">> (No output)" >&2
  fi

  echo -en "\033[6n"; IFS=';' read -sdR -a pos; curr_row="${pos[0]#*[}"; #curr_row=$((curr_row-1))

  if [[ $num_output_lines -lt "$DISPLAY_LINES" ]]; then
    # +2 if loader is enabled (probably), otherwise +1
    go_up_by=$((num_output_lines+2))
  else
    go_up_by=$((DISPLAY_LINES+1))
  fi


  set +eo pipefail
  wait "$cmd_pid"
  exit_code=$?

  goto_row "$((curr_row-go_up_by))"
  if [[ $exit_code -gt 0 ]]; then
    tail_stream "$ERR_DISPLAY_LINES"
  else
    print_empty_lines "$DISPLAY_LINES"
    goto_row "$((curr_row-go_up_by-1))"
  fi

  # echo -ne "$RESET"
  if [[ $exit_code -gt 0 ]]; then
    # echo ">>> running: $* (command exited with status $exit_code, full log available at: $logfile))" >&2
    echo ">>> command exited with status $exit_code (full log available at: $logfile)" >&2
    return "$exit_code"
  else
    echo ">>> success: $* (full log available at: $logfile)" >&2
    # echo ">>> command finished successfully (full log available at: $logfile)" >&2
  fi
)


run_command "$@"
# }

# stream_log_exec "$@"