防止shell脚本重复执行的代码
作者：
利用锁机制，让一个特定的shell脚本，每次只能运行一个实例。具体来说，获得锁的脚本实例，能够继续往下执行临界区代码；没有获得锁的实例，则只能等待
例如，要求脚本只能顺序访问某个资源，例如磁盘文件等，就可以参考下面的实现。
复制代码 代码如下:
#!/bin/bash
#
# file locking using bash.
# ver 0.1.6
#
# author : malundao ( malundao@sina.com )
# date : 2011-08-31
# ref : http://unix.derkeiler.com/Newsgroups/comp.unix.shell/2005-09/0472.html
#
# note:
# shflock_cleanhook() is a user defined function to clean up user-specific sth.
#
# /path/to/lock/. note; directory, not a file.
# should be modified
LOCKPATH="/tmp"
cleanup() {
shflock_cleanhook
cd $LOCKPATH
[ -e lock.pid ] || exit
read pid >/dev/null 2>&1 <lock.pid
if [ -n "$pid" ]; then
if [ "$pid" == "$$" ]; then
rm -f lock.$pid
rm -f lock.pid
exit
fi
fi
exit
}
# trap EXIT ?
trap 'cleanup' HUP INT TERM
getlock() {
oldpath=`pwd`
cd $LOCKPATH
while
echo $$ > lock.$$
[ -e lock.pid ]
do
rm lock.$$
read pid >/dev/null 2>&1 <lock.pid
if [ -n "$pid" ]; then
if [ -e /proc/$pid ]; then
cd $oldpath
return 1 # Lock is taken by others
else
#unsafe: rm -f lock.$pid
echo WARN: please delete stale lock.pid by HAND.
return 2
fi
else
# sleep some seconds,then back to 'while' loop
# 11 is a prime number, $$ as a random.
echo sleep $(( $$ % 11 ))
sleep $(( $$ % 11 ))
fi
done
# 'ln -s' is an atom op.
ln -s lock.$$ lock.pid >/dev/null 2>&1
if [ $? -eq 0 ]; then
cd $oldpath
return 0 # We got the lock
else
[ -e lock.pid ] || echo WARN: please delete hanging lock.pid by HAND.
cd $oldpath
return 3 # Lock is probably taken by others.
fi
}
putlock () {
oldpath=`pwd`
cd $LOCKPATH && rm -f lock.$$ lock.pid
cd $oldpath
}
## test
shflock_cleanhook() {
echo i\'m a hook.
}
while true; do
while ! getlock; do
#echo wait a second...
sleep 1
done
echo \[$$\] `date` ,now hold lock for 3 seconds...
sleep 3
#echo putlock
putlock
sleep 1 # yield
done
防止脚本多次执行（一）
复制代码 代码如下:
while [ `ps x |grep -v grep|grep filename.sh|wc -l` -gt 0 ];
do
exit
done
把内容放在脚本最上面
filename.sh 替换为你要监控的脚本名字
还有一种方法是 死循环 可以根据不同的环境，不同的脚本内容，使用的方法也同步，方法很简单日后在写出来