swatch.sh

#!/bin/bash

# Scroll watch: repeat command every INTERVAL and print/log only if output changes. Log or print only if something changes

# Default values
INTERVAL=2
LOGFILE="swatch.log"
QUIET=0

# Parse options
while [[ $# -gt 0 ]]; do
  case "$1" in
    -n)
      INTERVAL="$2"
      shift 2
      ;;
    -o)
      LOGFILE="$2"
      shift 2
      ;;
    -q|--quiet)
      QUIET=1
      shift
      ;;
    --)
      shift
      break
      ;;
    -*)
      echo "Unknown option: $1" >&2
      exit 1
      ;;
    *)
      break
      ;;
  esac
done

# Check if command is provided
if [ $# -eq 0 ]; then
  echo "Usage: $0 [-n seconds] [-o logfile] [-q|--quiet] <command>"
  exit 1
fi

PREV_OUTPUT=""

# Main loop
while true; do
  RAW_OUTPUT=$("$@")

  if [[ "$RAW_OUTPUT" != "$PREV_OUTPUT" ]]; then
    TIMESTAMP="--- $(date) ---"
    if [ "$QUIET" -eq 1 ]; then
      {
        echo ""
        echo "$TIMESTAMP"
        echo "$RAW_OUTPUT"
      } >> "$LOGFILE"
    else
      {
        echo ""
        echo "$TIMESTAMP"
        echo "$RAW_OUTPUT"
      } | tee -a "$LOGFILE"
    fi
    PREV_OUTPUT="$RAW_OUTPUT"
  fi

  sleep "$INTERVAL"
done