log-rotation.sh

#!/bin/bash
set -euo pipefail
cd $(dirname $0)
LOG_DIR="./log"
LOG_NAME="build-log"
ELOG_NAME="build-elog"
LOG_FILE="${LOG_DIR}/${LOG_FILE}"
ELOG_FILE="${LOG_DIR}/${ELOG_FILE}"

if [ ! -d "$LOG_DIR" ]; then
    mkdir -p "$LOG_DIR"
fi

MAX_GEN=1000
for i in $( seq $((MAX_GEN - 1)) -1 1); do
  if [ -f "${LOG_FILE}.$i" ]; then
    mv "${LOG_FILE}.$i" "${LOG_FILE}.$((i + 1))"
  fi
done
if [ -f ${LOG_FILE} ] ; then
  mv "${LOG_FILE}" "${LOG_FILE}.1"
  touch "${LOG_FILE}"
  chmod 644 "${LOG_FILE}"
fi

for i in $( seq $((MAX_GEN - 1)) -1 1); do
  if [ -f "${ELOG_FILE}.$i" ]; then
    mv "${ELOG_FILE}.$i" "${ELOG_FILE}.$((i + 1))"
  fi
done
if [ -f ${ELOG_FILE} ] ; then
  mv "${ELOG_FILE}" "${ELOG_FILE}.1"
  touch "${ELOG_FILE}"
  chmod 644 "${ELOG_FILE}"
fi

exec > >(tee -a "${LOG_FILE}")
exec 2> >(tee -a "${ELOG_FILE}")

# your commands following here