I was able to piece together an IDL program that makes some jpeg images I need. It works great when I call it from the command line (i.e., I type 'idl makejpegplots.pro'). The problem is I need to set the program to run at some point in the future, so I thought I'd use the handy unix 'at' command.  For example, I can say: echo "idl makejpegplots.pro" | at now + 2 minutes" I run many of my scripts this way instead of using a cron. At the given time, I know the code runs, because I get a jpeg file in my current working directory - but it's zero length! (whereas it's fine when run directly from the command line).  Now,  if I didn't get anything at all, I would suspect  a problem with the enviroment settings - but the fact that a jpeg file is created tells me this shouldn't be the case.  (If the IDL environment wasn't set, my program wouldn't have run at all).   My idl code does read from a file, and I was sure to give the fully-qualified path to the file.  So, I'm stumped, and unfortunately, the at command doesn't leave any trail of standard out that I can look at (despite having set the -m option to supposedly send me mail after it runs).  In my internet searches, I came across IDL_STARTUP.  I don't really understand what it does - but again since the code clearly ran - I'm not sure this has anything to do with my problem.   Any other suggestions??