How to load program reading stdin and taking parameters in gdb?

Question

I have a program that takes input from stdin and also takes some parameters from command line. It looks like this:

cat input.txt > myprogram -path "/home/user/work"

I try to debug the code with gdb inside emacs, by M-x gdb, I try to load the program with the command:

gdb cat input.txt > myprogram -path "/home/user/work"

However, gdb does not like it.

Question cribbed from here. Unfortunately I don't understand the solution and am not sure what to do beyond compiling with the -g option and running the command M-x gdb.

Answer 1

If you were doing it from a shell you'd do it like this:

% gdb myprogram
gdb> run params ... < input.txt

This seems to work within emacs too.

Answer 2

There are several ways to do it:

$ gdb myprogram
(gdb) r -path /home/user/work < input.txt

or

$ gdb myprogram
(gdb) set args -path /home/user/work < input.txt
(gdb) r

or

$ gdb -ex 'set args -path /home/user/work < input.txt' myprogram
(gdb) r

where the gdb run command (r) uses by default the arguments as set previously with set args.

Answer 3

For completeness' sake upon starting a debugging session there is also the --args option. ie)

gdb gdbarg1 gdbarg2 --args yourprog arg1 arg2 -x arg3

Answer 4

And if you do not need to debug from the very beginning you can also attach to an already running process by using:

$ gdb myprogram xxx

where xxx is the process id. Then you do not need to tell gdb the starting arguments.