Bless is a GUI hex editor for Linux. It is (surprisingly) written in Mono using GTK-Sharp as the GUI library! There are other GUI hex editors, but they have not been updated in years. There are command-line hex editors (like XXD or DHEX), but they are not as convenient to use as a GUI hex editor.
I mostly use Bless to examine a binary file. The most common operation for me is to examine 1/2/4 bytes at a certain location and check their value assuming they represent a signed or unsigned char, short or int. Thankfully, this is real easy to do in Bless. Just click on first byte in the display, it is displayed with red vertical bar (see screenshot above). The signed or unsigned char/short/int value of the following 1/2/4 bytes is displayed at the bottom. That is it! 🙂
Note: Bless seems to interpret the bytes as big-endian by default. Check the little-endian option at the bottom if you are using an Intel processor.
Tried with: Bless 0.6.0 and Ubuntu 14.04