Redirect all output to file using Bash on Linux? [duplicate]

I am trying to redirect all output from a command line programme to a file. I am using Bash. Some of the output is directed to a the file, but some still appears in the terminal and is not stored to the file.

Similar symptoms are described here:

Redirect all output to file

However I have tried the proposed solution (capture stderr) without success:

<cmd> <args> > stdout.txt 2> stderr.txt

The file stderr.txt is created but is empty.

A possible clue is that the command-line programme is a client communicating with a server on the same machine. It may be that some of the output is coming from the server.

Is there a way to capture all the output from the terminal, irrespective of its origin?

EDIT:

I've confirmed that the missing output is generated by the server. Running the command in a separate terminal causes some output in both terminals, I can pipe all the output from the command terminal to a file. This raises issues about how to capture the server output, but that's a different question.

Solution 1:

you can use this syntax to redirect all output stderr and stdout to stdout.txt

<cmd> <args> > allout.txt 2>&1 

Solution 2:

Though not POSIX, bash 4 has the &> operator:

command &> alloutput.txt

Solution 3:

If the server is started on the same terminal, then it's the server's stderr that is presumably being written to the terminal and which you are not capturing.

The best way to capture everything would be to run:

script output.txt

before starting up either the server or the client. This will launch a new shell with all terminal output redirected out output.txt as well as the terminal. Then start the server from within that new shell, and then the client. Everything that you see on the screen (both your input and the output of everything writing to the terminal from within that shell) will be written to the file.

When you are done, type "exit" to exit the shell run by the script command.