How to attach a process in gdb

Question

I have a simple C program that forks a process and then runs an executable.

I want to attach the child process to gdb.

I run the main program in a console and open another console to find the pid of the child process, then I start gdb with the following command:

gdb attach 12271

where 12271 is the child process id, but the attach fails with:

No such file or directory.

Any idea why?

i don't think attach is a command line argument. you can use it once gdb is already running. this guy has a good tutorial: http://dirac.org/linux/gdb/06-Debugging_A_Running_Process.php — thang, Jan 17 '13 at 01:51
Possible duplicate of [Can I use GDB to debug a running process?](http://stackoverflow.com/questions/2308653/can-i-use-gdb-to-debug-a-running-process) — Ciro Santilli Путлер Капут 六四事, Feb 17 '16 at 17:35

score 131 · Accepted Answer · edited Feb 09 '17 at 17:59

131

Try one of these:

gdb -p 12271
gdb /path/to/exe 12271

gdb /path/to/exe
(gdb) attach 12271

edited Feb 09 '17 at 17:59

Yostage

answered Jan 17 '13 at 03:02

Employed Russian

DrC · Answer 2 · 2013-01-17T22:10:16.067

22

The first argument should be the path to the executable program. So

gdb progname 12271

edited Jan 17 '13 at 22:10

answered Jan 17 '13 at 01:53

DrC

Stephane Rolland · Answer 3 · 2020-10-28T15:49:00.767

7

With a running instance of myExecutableName having a PID 15073:

hitting Tab twice after $ gdb myExecu in the command line, will automagically autocompletes to:

$ gdb myExecutableName 15073

and will attach gdb to this process. That's nice!

edited Oct 28 '20 at 15:49

answered Feb 28 '19 at 08:45

Stephane Rolland

3 Answers3