Step1：查看进程id

输入ps或ps -ef

root@TinaLinux:/proc/631/fd# ps
PID   USER     TIME   COMMAND
    1 root       0:03 /sbin/procd
...........
  631 root       0:06 ./rt_agent
  694 root       0:00 [kworker/2:2]
  771 root       0:23 /home/upg/fupg

要查看的进程id为631。

Step2：查看标准输出

切换到/proc/<pid>/fd下，如

root@TinaLinux:~# cd /proc/631/fd
root@TinaLinux:/proc/631/fd# ls
0  1  2  3  4  5  6  7  9

目录中的每一项都是一个符号链接，指向打开的文件，数字则代表文件描述符。其中1 = stdout, 2 = stderr，用cat或tail查看即可。

root@TinaLinux:/proc/631/fd# cat 1
E0831 17:44:23.777757   784 mqtt_api.c:159] fupg:: Connect failed, rc 0xb6087ccc
I0831 17:44:23.778110   784 mqtt_api.c:162] fupg:: response->message : CONNACK return code
E0831 17:44:32.586987   784 mqtt_api.c:159] fupg:: Connect failed, rc 0xb6087ccc
I0831 17:44:32.656756   784 mqtt_api.c:162] fupg:: response->message : CONNACK return code
E0831 17:44:41.649714   784 mqtt_api.c:159] fupg:: Connect failed, rc 0xb6087ccc
I0831 17:44:41.650127   784 mqtt_api.c:162] fupg:: response->message : CONNACK return code
375470][  85 rt_ipc_server.c]g_rt_ipc_cmd begin...

[DBG  ][2021-08-31 17:27:41.737][0xb4b75470][  99 rt_port_at.c]rt_port_impl_at_command cmd: (AT+CEREG?
).

[DBG  ][2021-08-31 17:29:29.832][0xb1dff470][ 337 Socket.c]<-D0
[DBG  ][2021-08-31 17:44:15.670][0xb1dff470][ 337 Socket.c]<-00
[DBG  ][2021-08-31 17:44:15.670][0xb3375470][  99 rt_port_at.c]rt_port_impl_at_command cmd: (AT+CSQ

).

[DBG  ][2021-08-31 17:44:15.680][0xb4b75470][ 202 rt_port_at.c]rt_port_impl_at_command rsp: (
+CEREG: 0,1

OK