I think this was asked in another question but I'm looking for a SVN client that can handle gui and command-line commands.
For example a developer would like a gui to work with but a script would find it easier to issue commands directly on the command line. Installing one of the gui clients in addition to the svn command line client could lead to a version conflict so I was wondering if there was any client that can handle both.
Just use whatever you like SVN GUI client, and get original SVN client binary from subversion.org. This way you will get GUI and in case if you want command line, just open your command prompt and issue commands directly.
And yes, TortoiseSVN and SVN command-line client don't have any problems with each other.
You don't say which platform, but for Windows the simple solution is to install two clients. I use Tortoise SVN as a GUI and Slik SVN as a command line client. They work perfectly well together. Tortoise SVN actually has a command line interface, described here, but it is nowhere near as flexible and useful as a dedicated command line client.
The Subclipse plugin for Eclipse allows you to use JavaHL to connect to the same Subversion libraries you use in the command line.
The tortoise SVN client for windows is actually invoked from explorer using simple command-line switches. You can automate these if you want in a script, a little info from the manual: http://tortoisesvn.net/docs/nightly/TortoiseSVN%5Fen/tsvn-automation.html