Conditional Commands
When an internal command or external program finished, it returns a result
called the exit code. Conditional commands allow you to perform tasks
based upon the previous command's exit code. Many programs return a 0 if
they are successful and a non-zero value if they encounter an error.
If you separate two commands by && (AND), the second command will be
executed only if the first returns an exit code of 0. For example, the
following command will only erase files if the BACKUP operation succeeds:
[c:\] backup c:\ a: && del c:\*.bak;*.lst
If you separate two commands by || (OR), the second command will be
executed only if the first returns a non-zero exit code. For example, if
the following BACKUP operation fails, then ECHO will display a message:
[c:\] backup c:\ a: || echo Error in the backup!
All internal commands return an exit code, but not all external programs
do. Conditional commands will behave unpredictably if you use them with
external programs which do not return an explicit exit code. To determine
whether a particular external program returns a meaningful exit code use
an ECHO %? command immediately after the program is finished. If the
program's documentation does not discuss exit codes you may need to
experiment with a variety of conditions to see how the exit code changes.
Created using Inf-PHP v.2 (c) 2003 Yuri Prokushev
Created using Inf-HTML v.0.9b (c) 1995 Peter Childs