确保同一时间只有一个shell脚本实例在运行的方法

#! /bin/bash

(
  # Wait for lock on /var/lock/.myscript.exclusivelock (fd 200) for 10 seconds
  flock -x -w 10 200 || exit 1

  # 在这里放置脚本的主逻辑部分

) 200>/var/lock/.myscript.exclusivelock

SCRIPT_NAME=$(basename "$0")
LOCKFILE=/tmp/${SCRIPT_NAME}.lock
if [ -e ${LOCKFILE} ] && kill -0 `cat ${LOCKFILE}`; then
    echo "already running"
    exit
fi

# make sure the lockfile is removed when we exit and then claim it
trap "rm -f ${LOCKFILE}; exit" INT TERM EXIT
echo $$ > ${LOCKFILE}

# 在这里放置脚本的主逻辑部分
sleep 100

rm -f ${LOCKFILE}