在 shell 脚本中将交互式命令作为后台进程运行

Question

I am facing an issue when I am trying to run a interactive command/app in the background of the shell script. I am trying to log the output of the command to a file. But I don't see that command logging anything to the file. Even executing the command in the bash also did not work as it gets suspended.

Sample script

#!/bin/bash
while true
do
./a.out > test &
PID=$!
sleep 20
kill -9 $PID
done

[@myprog]$ ./a.out &
[1] 3275
Program started

[1]+  Stopped                 ./a.out
[@myprog]$ 

Answer 1

You don't need to create a background process to redirect data. You can do the following, which will create a logfile actions.log which holds your every action.

#! /bin/bash

while read -p "action " act; do
        echo $act
done > actions.log
exit 0

For you, this would be something like:

$ a.out > test.log

If you do want to have a background process, but need to input data:

$ function inter_child {
    ./inter.sh  <<-EOF
a
b
c
d
EOF
sleep 10
}
$ inter_child &
$ wait
$ cat actions.log 
a
b
c
d

If this doesn't answer your question, please be more specific why you need to create a child process and what's a.out is expecting. Hope this helps!

EDIT:
stdout and stderr are two different redirections.
Write stderr to file 2> : $ ./a.out 2> error.log
Redirect stderr to stdout 2>&1 : $ ./a.out > log.log 2>&1