Using gdb, the Gnu Debugger

• Compile your program with the -g option (gcc -g file.c)
• The executable and the source should be in the same directory. To start the debugger
  gdb executable for example gdb a.out
• Most commands can be invoked by their first letter; you do not need to type the entire word.
• Before running the program, set one or more breakpoints with the break command. These can be set either at line numbers or at the start of functions. For example
  
  

  b 136	break at line 136, or
  b fctnOne	breaks at the start of fctnOne

Here are some more useful commands.

run

starts running the program. This will run to the first breakpoint. You can pass arguments to the run command; this passes arguments to your program. For example
r arg1 arg2

print

displays the value of a variable or expression

display

Display the value of a variable or expression at each step

step

steps through the program a line at a time, stepping into functions.

next

steps through the program a line at a time, stepping over functions

finish

run to the end of the current function (useful if you step into a function by mistake)

continue

runs to the next breakpoint

list

shows the source code

quit

terminates the debugger

help

gets more information