168 lines
3.9 KiB
Markdown
168 lines
3.9 KiB
Markdown
<h1><center>shell并发控制</center></h1>
|
||
|
||
|
||
|
||
------
|
||
|
||
## 一：FD文件描述符
|
||
|
||
#### 1.FD简述
|
||
|
||
FD：文件描述符/文件句柄
|
||
|
||
进程使用文件描述符用来管理进程打开的文件
|
||
|
||
```shell
|
||
[root@xingdiancloud ~]# ll /proc/$$/fd
|
||
总用量 0
|
||
lrwx------. 1 root root 64 4月 16 23:51 0 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 1 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 2 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 255 -> /dev/pts/0
|
||
[root@xingdiancloud ~]# touch file1
|
||
启用自定义文件描述符打开文件
|
||
[root@xingdiancloud ~]# exec 6<> file1
|
||
[root@xingdiancloud ~]# ll /proc/$$/fd
|
||
总用量 0
|
||
lrwx------. 1 root root 64 4月 16 23:51 0 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 1 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 2 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 255 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 6 -> /root/file1
|
||
[root@xingdiancloud ~]# echo "xingdian" > /proc/$$/fd/6
|
||
[root@xingdiancloud ~]# cat file1
|
||
xingdian
|
||
[root@xingdiancloud ~]# rm -rf file1
|
||
[root@xingdiancloud ~]# ll /proc/$$/fd
|
||
总用量 0
|
||
lrwx------. 1 root root 64 4月 16 23:51 0 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 1 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 2 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 255 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 6 -> '/root/file1 (deleted)'
|
||
[root@xingdiancloud ~]# cat /proc/$$/fd/6
|
||
xingdian
|
||
释放文件描述符
|
||
[root@xingdiancloud ~]# exec 6<&-
|
||
[root@xingdiancloud ~]# ll /proc/$$/fd
|
||
总用量 0
|
||
lrwx------. 1 root root 64 4月 16 23:51 0 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 1 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 2 -> /dev/pts/0
|
||
lrwx------. 1 root root 64 4月 16 23:51 255 -> /dev/pts/0
|
||
```
|
||
|
||
注意：
|
||
|
||
exec打开一个文件
|
||
|
||
exec关闭一个文件(释放文件句柄)
|
||
|
||
当一个文件FD未被释放，删除源文件也不会影响FD
|
||
|
||
#### 2.管道简述
|
||
|
||
匿名管道
|
||
|
||
```shell
|
||
[root@xingdiancloud ~]# rpm -qa | grep rpm
|
||
```
|
||
|
||
命令管道
|
||
|
||
```shell
|
||
[root@xingdiancloud ~]# mkfifo /tmp/xingdian
|
||
[root@xingdiancloud ~]# file /tmp/xingdian
|
||
/tmp/xingdian: fifo (named pipe)
|
||
[root@xingdiancloud ~]# tty
|
||
/dev/pts/0
|
||
[root@xingdiancloud ~]# rpm -qa > /tmp/xingdian
|
||
|
||
另一个终端
|
||
[root@xingdiancloud ~]# grep bash /tmp/xingdian
|
||
bash-5.1.8-6.el9.x86_64
|
||
bash-completion-2.11-4.el9.noarch
|
||
[root@xingdiancloud ~]# tty
|
||
/dev/pts/1
|
||
```
|
||
|
||
#### 3.FD案例
|
||
|
||
```shell
|
||
[root@xingdiancloud ~]# cat a.sh
|
||
#!/bin/bash
|
||
exec 7<> /etc/hosts
|
||
exec 8<> /etc/hostname
|
||
|
||
while read -u 7 line
|
||
do
|
||
echo $line
|
||
done
|
||
while read -u 8 line2
|
||
do
|
||
echo $line2
|
||
done
|
||
exec 7<&-
|
||
exec 8<&-
|
||
|
||
[root@xingdiancloud ~]# bash a.sh
|
||
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
|
||
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
|
||
xingdiancloud
|
||
```
|
||
|
||
4.并发案例
|
||
|
||
```shell
|
||
#!/usr/bin/bash
|
||
#固定线程
|
||
read -p "请输入线程数量：" diange
|
||
diangefile=/root/diangefile
|
||
mkfifo $diangefile //虚拟管道
|
||
exec 8<>$diangefile //文件描述
|
||
rm -rf $diangefile
|
||
|
||
for i in `seq $diange`
|
||
do
|
||
echo >&8 //将内容写入到描述文件中,写如了空行
|
||
done
|
||
|
||
for i in {1..100}
|
||
do
|
||
read -u 8 //read 读取描述文件中的内容
|
||
{
|
||
ip=192.168.101.$i
|
||
ping -c1 $ip &>/dev/null
|
||
if [ $? -eq 0 ];then
|
||
echo "$ip is up"
|
||
else
|
||
echo "$ip is down"
|
||
|
||
fi
|
||
echo >&8 //等到进程执行完之后再往管道里丢内容以支持后面的循环
|
||
}&
|
||
done
|
||
wait
|
||
echo "完成"
|
||
exec 8<&- //释放描述文件
|
||
```
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|