iowatchd 0.5.2

Monitors disk IO usage and logs which processes are consuming it
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#!/usr/bin/env bash
# iowatchd-log - show the alerts logged by iowatchd.
set -u

usage() {
  cat <<'EOF'
Usage: iowatchd-log [OPTIONS] [N]

Show the alerts logged by iowatchd.

Options:
  -n, --lines N      show the last N lines (default: 50; a bare N also works)
  -f, --follow       follow the log in real time
      --since WHEN   only entries since WHEN, e.g. "2026-10-17 08:00",
                     "1 hour ago", "yesterday" (GNU date syntax)
  -j, --json         only JSON entries (pretty-printed when jq is installed)
  -s, --status       show the service status
      --no-pager     do not page the --status output
  -h, --help         show this help

The log file is taken from log_file in /etc/iowatchd.conf (or the file named
by $IOWATCHD_CONFIG). Set $IOWATCHD_LOG to override it. When file logging is
disabled the systemd journal is used instead.
EOF
}

die() { echo "iowatchd-log: $*" >&2; echo "Try 'iowatchd-log --help' for more information." >&2; exit 2; }

lines="" follow=0 status=0 since="" json=0 nopager=0
while [ $# -gt 0 ]; do
  case $1 in
    -n|--lines)  [ $# -ge 2 ] || die "option '$1' requires a value"; lines=$2; shift ;;
    --lines=*)   lines=${1#*=} ;;
    -f|--follow) follow=1 ;;
    --since)     [ $# -ge 2 ] || die "option '$1' requires a value"; since=$2; shift ;;
    --since=*)   since=${1#*=} ;;
    -j|--json)   json=1 ;;
    -s|--status) status=1 ;;
    --no-pager)  nopager=1 ;;
    -h|--help)   usage; exit 0 ;;
    -n[0-9]*)    lines=${1#-n} ;;
    -[0-9]*|[0-9]*) lines=${1#-} ;;
    *)           die "unknown option or argument '$1'" ;;
  esac
  shift
done

case $lines in ''|*[!0-9]*) [ -z "$lines" ] || die "invalid number of lines: '$lines'" ;; esac

if [ "$status" = 1 ]; then
  if [ -d /run/systemd/system ]; then
    if [ "$nopager" = 1 ]; then exec systemctl status iowatchd --no-pager; fi
    exec systemctl status iowatchd
  elif command -v rc-service >/dev/null 2>&1; then exec rc-service iowatchd status
  else exec sv status iowatchd; fi
fi

# Value of log_file in the configuration; fails if the key is not set.
conf_log_file() {
  local conf=${IOWATCHD_CONFIG:-/etc/iowatchd.conf}
  [ -r "$conf" ] || return 1
  awk '{
    sub(/#.*/, "")
    if ($0 ~ /^[ \t]*log_file[ \t]*=/) {
      v = $0; sub(/^[^=]*=/, "", v); gsub(/^[ \t]+|[ \t]+$/, "", v)
      val = v; found = 1
    }
  } END { if (found) print val; else exit 1 }' "$conf"
}

LOG=${IOWATCHD_LOG:-}
if [ -z "$LOG" ]; then
  if LOG=$(conf_log_file); then :; else LOG=/var/log/iowatchd.log; fi
fi

# Keep only JSON lines, pretty-printed when jq is available.
json_filter() {
  if command -v jq >/dev/null 2>&1; then jq -R 'fromjson? // empty'
  else grep --line-buffered '^{'; fi
}
maybe_json() { if [ "$json" = 1 ]; then json_filter; else cat; fi; }

# Journal fallback when file logging is disabled (log_file empty).
if [ -z "$LOG" ]; then
  args=(-u iowatchd --no-pager -o cat)
  [ -n "$lines" ] && args+=(-n "$lines")
  [ -z "$lines" ] && [ -z "$since" ] && args+=(-n 50)
  [ -n "$since" ] && args+=(--since "$since")
  [ "$follow" = 1 ] && args+=(-f)
  journalctl "${args[@]}" | maybe_json
  exit "${PIPESTATUS[0]}"
fi

[ -r "$LOG" ] || { echo "iowatchd-log: cannot read $LOG (no alerts logged yet?)" >&2; exit 1; }

if [ -n "$since" ]; then
  [ "$follow" = 0 ] || die "--since cannot be combined with --follow"
  from=$(date -d "$since" '+%Y-%m-%d %H:%M:%S' 2>/dev/null) || die "invalid date: '$since'"
  # Lines carry a "YYYY-MM-DD HH:MM:SS" timestamp (text and JSON formats).
  awk -v s="$from" '
    match($0, /[0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9] [0-9][0-9]:[0-9][0-9]:[0-9][0-9]/) {
      p = (substr($0, RSTART, 19) >= s)
    }
    p' "$LOG" | { if [ -n "$lines" ]; then tail -n "$lines"; else cat; fi; } | maybe_json
elif [ "$follow" = 1 ]; then
  tail -n "${lines:-20}" -F "$LOG" | maybe_json
else
  tail -n "${lines:-50}" "$LOG" | maybe_json
fi