zuhakasa zuhakasa - 1 year ago 50
C Question

How to passing input data in GDB mode for programming C. Already passed parameters and run program

I already know how to pass parameters in GDB mode by running: "run parameters". However, when continuing to debug by using n or s to go, I would like to pass data to my program, let say a text/string. For example, I want to send a string as "Testing" to my program because my program always waits to receive command from console. If I type "Testing" it will say "undefined command: "Testing". Try help".

(gdb) b 100
(gdb) run "pass parameters to program here"
(gdb) n
(gdb) Now I want to send a string to my program, how can I do it?

So how can I do to send this text to my program while debugging GDB in step mode? Thanks very much.

Answer Source

For real, just type it in. Sample session:

paul@local:~/src/c/scratch$ gdb ./deb
GNU gdb (GDB) 7.4.1-debian
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
Reading symbols from /home/paul/src/c/scratch/deb...done.
(gdb) list
1   #include <stdio.h>
3   int main(void) {
4       char buffer[100];
5       fgets(buffer, 100, stdin);
6       printf("You entered: %s", buffer);
7       return 0;
8   }
(gdb) break 4
Breakpoint 1 at 0x400644: file deb.c, line 4.
(gdb) run
Starting program: /home/paul/src/c/scratch/deb 

Breakpoint 1, main () at deb.c:5
5       fgets(buffer, 100, stdin);
(gdb) n
Hello, world!
6       printf("You entered: %s", buffer);
(gdb) n
You entered: Hello, world!
7       return 0;
(gdb) continue
[Inferior 1 (process 4290) exited normally]

The Hello, world! after the first n was just typed in normally.