The usual way to examine data in your program is with the print
command (abbreviated p), or its synonym inspect. It
evaluates and prints the value of an expression of the language your
program is written in (see Using GDB with Different Languages).
print expr
print /f expr
/f, where
f is a letter specifying the format; see Output formats.
print
print /f
A more low-level way of examining data is with the x command.
It examines data in memory at a specified address and prints it in a
specified format. See Examining memory.
If you are interested in information about types, or about how the
fields of a struct or a class are declared, use the ptype exp
command rather than print. See Examining the Symbol Table.