Question

There are lots of GUI best practices. I am looking for best practices when developing a command line program.

For example, if I were creating a backup program what is best?

Consideration 1, invocation:

program.exe backup

program.exe /backup

program.exe -backup

program.exe –backup

Consideration 2, parameters:

program.exe backup “C:\file1.txt” “C:\file1.bak” (implicit source and destination)

program.exe backup -source “C:\file1.txt” -destination “C:\file1.bak” (explicit)

program.exe backup -source “C:\file1.txt” “C:\file2.txt” “C:\file3.txt” -destination “C:\files.bak” (multiple sources)

program.exe backup -source “C:\file1.txt” -source “C:\file2.txt” -source “C:\file3.txt” -destination “C:\files.bak” (multiple sources, alternative syntax)

Consideration 3, chaining:

program.exe backup “C:\file1.txt” “C:\file1.bak” backup “C:\file2.txt” “C:\file2.bak” (should this be allowed?)

Consideration 4, typing economy:

program.exe backup

program.exe bkp

program.exe b (should all these be aliases to the same command?)

Answer 1

I’d always prefer what’s (in order of importance from most to least):

• Most understandable by the end user
• Least ambiguous
• Follows the conventions of the platform being coded against
• Easiest to parse in my code

So on Windows I’d go for / as the prefix (follows the conventions), /source and /destination (most understandable AND least ambiguous) and not allow chaining as that makes for parsing complexity, so:

program.exe /backup /source:”c:\source” /destination:”c:\destination”

By all means also permit abbreviated versions of the parameter names, so you could allow the above to be shrunk down to:

program.exe /b /s:”c:\source” /d:”c:\destination”

But don’t make it any more arcane than that. Also, include a /? parameter that can be used to list the syntax for your program. As Peter M pointed out in the comments on my answer, it’s a good idea to do the same as /? when the user calls your program without specifying any parameters. Nothing’s less helpful and more frustratingly useless than running a CLI program and receiving:

Program Name v1.01

No parameters specified, use /? for help

One other important thing to consider, tied to the final point, would be: don’t reinvent the wheel. There are innumerable Command Line Parsers out there, take a look at the answers to this question for a starting point (if you’re using C# targeting Windows). Don’t do a mediocre job of doing something that someone else has already done a good job of doing.