LINUX IO重定向

Posted 2020-11-05

/proc 文件存储进程信息
[[email protected] ~]# ls /proc
1 1168 17 226 25 28 38 469 491 8104 823 bus devices filesystems kallsyms kpageflags modules sched_debug stat timer_stats zoneinfo
10 12 18 232 250 3 39 473 5 8129 850 cgroups diskstats fs kcore loadavg mounts schedstat swaps tty

[[email protected] ~]# ls /proc/8225/fd
0 1 2 3

[[email protected] ~]# ll /proc/8225/fd
total 0
lrwx------ 1 root root 64 May 16 09:58 0 -> /dev/pts/2
lrwx------ 1 root root 64 May 16 09:58 1 -> /dev/pts/2
lrwx------ 1 root root 64 May 16 09:58 2 -> /dev/pts/2
lrwx------ 1 root root 64 May 16 09:58 3 -> /root/.a.txt.swp
/proc/PID/fd这个文件能显示进程打开文件数量
进程使用描述符来管理打开文件
0标准输入stdin keyboard read
1标准输出stdout teminal write
2标准错误stderr teminal write
3，4，5，6。。。。。。其它文件
[[email protected] ~]# ls /ddfjlsfjslf &>list1.txt
&符号将正确错误的信息放置同一个文件中
[[email protected] ~]# ls /jslfjslf >/dev/null，空设备
如果/dev/null设备被删除
1.手动创建
mknod -m 666 /dev/null c 1 3
2.重启自动创建

[[email protected] ~]# ll /dev/null
crw-rw-rw- 1 root root 1, 3 May 15 14:24 /dev/null
主设备号 从设备号
block设备有缓存
mknod：mknod - make block or character special files
mknod [OPTION]... NAME TYPE [MAJOR MINOR]
TYPE may be:

   b      create a block (buffered) special file

   c, u   create a character (unbuffered) special file

   p      create a FIFO