You can use this for files:
and this for folders:
zenity --file-selection --directory
for usage, run:
Generally it matches the current theme (for GTK window managers anyway), on my machine with a modded version of Zukitwo 3.8 it looks like this:
One way of using it is like this:
echo "you selected $(zenity --file-selection)"
Which would result in
you selected /path/to/file.
You can also use options to set an appropriate title, and the directory it starts in - With your rsync use case, for example:
zenity --file-selection --directory --title="Choose rsync source directory" --filename=$HOME/Desktop/
For files, you can also specify a filetype to select - e.g:
zenity --file-selection --file-filter='PDF files (pdf) | *.pdf' --title="Select a PDF file"
NOTE: You can also use YAD, a fork of Zenity that has loads more features.
sudo add-apt-repository ppa:webupd8team/y-ppa-manager
sudo apt-get update
sudo apt-get install yad
For the most part you can use it the same way - for the file browser:
and for the help page:
Though at the time (around version 26?), it had not been updated to match the new GTK 3.14+ interface (zenity had) - it has more features, but check compatibility (based on documentation it should work on GTK+ >= 2.16.0