"exec not found" when using variable in exec
It is caused by shell not performing variable expansion on the left side of the redirection operator. You can use a workaround:
eval exec "${PIPE_ID}"'<>"spch2008"'It will force the shell to do variable expansion, producing
eval exec 100'<>"spch2008"'Then the eval built-in will feed the command to the shell, which will effectively execute
exec 100<>"spch2008"
I/O redirection doesn't allow variables to specify the file descriptors generally, not just in the context of the <> redirection.
Consider:
$ cat > errmsg # Create scriptecho "$@" >&2 # Echo arguments to standard error$ chmod +x errmsg # Make it executable$ x=2$ ./errmsg Hi # Writing on standard errorHi$ ./errmsg Hi ${x}>&1 # Writing on standard errorHi 2$ ./errmsg Hi 2>&1 # Redirect standard error to standard outputHi$ ./errmsg Hi 2>/dev/null # Standard error to /dev/null$ ./errmsg Hi ${x}>/dev/null # Standard output to /dev/nullHi 2$