IDl save the command line to file

IDL> journal, 'my_tutorial_1.log'
Please do this now! BUT BEWARE! BEWARE BEWARE! If you try to start a journal file using a name of a file that already exists, that file will be erased and over-written! Always
use a unique journal file name every time you start journaling, otherwise you will lose your previous journal entries!

All subsequent commands you enter at the IDL command line and their outputs will go into this file. When you want to close the journal file, simply type the journal command again, all by itself at the IDL command line. Hence, when you are done
with this tutorial or need to exit IDL, please remember to close the journal file by typing:
IDL> journal
The journal file is a simple ASCII text file that you can edit, if you like, with any text editor. Please remember to examine your my_tutorial_1.log file after exiting out of IDL. You cannot append to journal files, so
if you open a second file with the same name as the first one, many operating systems will simply overwrite the first journal file without warning.