The "can't re-open pipe to command substitution (fd 4): No child processes" error usually occurs when you are using the cat command to read from a pipe that has already been closed, or when you are using a command substitution (e.g., $(...)) within a script or command and the command substitution has already been run.
Here are a few possible solutions for this error:
Make sure that the command substitution is being run only once, and not multiple times. For example, if you are using a loop to run the command substitution, make sure that the loop is not running the command multiple times.
Make sure that the command substitution is being run within a subshell. You can do this by enclosing the command substitution in parentheses (e.g., $(...)). This will cause the command substitution to be run in a subshell, which will prevent the error from occurring.
Make sure that the command substitution is being run in a separate shell. You can do this by using the bash command to run the command substitution in a new shell. For example:
bash -c "$(...)";Sourceual.www:tturi.com
Make sure that the command being run within the command substitution is being closed properly. If the command is not being closed properly, the pipe to the command substitution may remain open, causing the error to occur.
Make sure that you are not using the cat command to read from a pipe that has already been closed. If you are using the cat command to read from a pipe, make sure that the command that is writing to the pipe is still running. If the command has already finished running, the pipe will be closed and the cat command will not be able to read from it.
By following these steps, you should be able to resolve the "can't re-open pipe to command substitution (fd 4): No child processes" error.