linux下监视进程 崩溃挂掉后自动重启的shell脚本
如何保证服务一直运行？如何保证即使服务挂掉了也能自动重启？在写服务程序时经常会碰到这样的问题。在Linux系统中，强大的shell就可以很灵活的处理这样的事务。
下面的shell通过一个while-do循环，用ps -ef|grep 检查loader进程是否正在运行，如果没有运行，则启动，这样就保证了崩溃挂掉的进程重新被及时启动。
必须注意两点：
1、ps |grep 一个进程时必须加上其路劲，否则容易grep到错误的结果；
2、必须用 -v 从结果中去除grep命令自身，否则结果非空。
#!/bin/sh#=====================#YuanHui.HE
#khler@
#=====================
while:do
echo "Current DIR is"$PWD
stillRunning=$(ps -ef |grep "$PWD/loader" |grep -v "grep")if [ "$stillRunning" ] ; then
echo "TWS service was already started by another way"
echo "Kill it and then startup by this shell, other wise this shell will loop out this message annoyingly"
kill -9 $pidof $PWD/loaderelse
echo "TWS service was not started"
echo "Starting service ..."$PWD/loaderecho "TWS service was exited!"
fi
sleep 10
done
如果启动此shell时发现进程已经存在，说明以别的方式启动了进程而不是此shell，那么它会持续提醒找到进程，解决办法是，要么只用此shell启动服务，要么一经发现以其他方式启动的服务即kill掉，上面的语句就是这么干的：
kill -9 $pidof $PWD/loader
判断文件是否存在的shell脚本代码
实现代码一、
#!/bin/sh# 判断文件是否存在
# link：
#date：/2/28myPath="/var/log/httpd/"myFile="/var /log/httpd/access.log"# 这里的-x 参数判断$myPath是否存在并且是否具有可执行权限if [ ! -x "$myPath"]; then
mkdir "$myPath"
fi# 这里的-d 参数判断$myPath是否存在if [ ! -d "$myPath"]; then
mkdir "$myPath"
fi# 这里的-f参数判断$myFile是否存在if [ ! -f "$myFile" ]; then
touch "$myFile"
fi# 其他参数还有-n,-n是判断一个变量是否是否有值if [ ! -n "$myVar" ]; then
echo "$myVar is empty"exit0
fi# 两个变量判断是否相等if [ "$var1" = "$var2" ]; then
echo '$var1 eq $var2'
else
echo '$var1 not eq $var2'
fi
实现代码二、
#shell判断文件夹是否存在
#如果文件夹不存在，创建文件夹if [ ! -d "/myfolder" ]; then
mkdir /myfolderfi#shell判断文件,目录是否存在或者具有权限
folder="/var/www/"
file="/var/www/log"#-x 参数判断 $folder 是否存在并且是否具有可执行权限if [ ! -x "$folder"]; then
mkdir "$folder"
fi#-d 参数判断 $folder 是否存在if [ ! -d "$folder"]; then
mkdir "$folder"
fi#-f 参数判断 $file是否存在if [ ! -f "$file" ]; then
touch "$file"
fi#-n 判断一个变量是否有值if [ ! -n "$var" ]; then
echo "$var is empty"exit0
fi# 判断两个变量是否相等if [ "$var1" = "$var2" ]; then
echo '$var1 eq $var2'
else
echo '$var1 not eq $var2'
fi
-f 和-e的区别
Conditional Logic on Files
-a file exists.
-b file exists and is a block special file.
-c file exists and is a character special file.
-d file exists and is a directory.
-e file exists (just the same as -a).
-f file exists and is a regular file.
-g file exists and has its setgid(2) bit set.
-G file exists and has the same group ID as this process.
-k file exists and has its sticky bit set.
-L file exists and is a symbolic link.
-n string length is not zero.
-o Named option is set on.
-O file exists and is owned by the user ID of this process.
-p file exists and is a first in, first out (FIFO) special file or
named pipe.
-r file exists and is readable by the current process.
-s file exists and has a size greater than zero.
-S file exists and is a socket.
-t file descriptor number fildes is open and associated with a
terminal device.
-u file exists and has its setuid(2) bit set.
-w file exists and is writable by the current process.
-x file exists and is executable by the current process.
-z string length is zero.
是用 -s 还是用 -f 这个区别是很大的！
在指定目录查找指定后缀文件的shell脚本代码
#!bin/sh# 在指定位置查找指定后缀的文件,包括子目录
# 用法:
# findf $1 $2# 第一个参数为后缀
# 查找指定后缀的文件并打印出来
# link：
#date：/2/26f()
{
list=`find $2|grep "/.$1/>"`for i in$listdo
echo$idone}
# 打印用法
print()
{echo "用法:"
echo "$1 /$1 /$2"
echo "第一个参数为指定的后缀名,如'h'"
echo "第二个参数为指定的目录,如果省略此参数则默认为当前目录"exit-1}
# 在当前目录查找
f1()
{
f"$1" "*"}
# 在指定的目录查找
f2()
{
cd $2f"$1" "*"}if [ "$#" -lt "1"]then
echo "给定的参数太少,最少需要一个参数."print"$0"
fi
if [ "$#" -gt "2"]then
echo "给定的参数太多,最多需要二个参数."print"$0"
fi
if [ "$#" -eq "1"]thenf1 $1exit0
fi
if [ "$#" -eq 2]thenf2 $1 $2exit0
fi
