I have gdb running on cpp application process on remote machine, and accidenttly close terminal. How do i get into this gdb shell again?
$ pidof application
12345
$ pidof gdb
23456
gdb was started like "gdb --pid=12345" which is attached to process.
How do I get back into gdb shell from external shell. Is there any way like
"enter-gdb-shell with pid 23456"
reptyr does what you want: attach a terminal to a running process.
I am trying to debug GDB itself and dealing with a Ctrl+C signal problem that is sent from another terminal.
I run GDB to be debugged in terminal 1 in TUI mode. Right after, I open another terminal 2 and find the PID number of the GDB that runs on Terminal 1. Then attach that process to debug.
In Terminal 1
$ build-gdb/gdb/gdb -tui ./build/output.elf -tty=$TTY
In Terminal 2
$ ps -elf | less
$ sudo gdb -p PID_NUMBER-tty=$TTY -tui
The problem is when I hit Ctrl+C to stop GDB in terminal 1, GDB runs on Terminal 2 stops. GDB in Terminal 1 does not responds to ^C command at all. I tried to use -tty parameter and get the current TTY, but id did not solved the problem. GDB uses readline GNU library, but i should be configure terminal and its input properly.
Any idea?
You can use
handle SIGINT pass
to instruct GDB to pass the signal to the inferior. See Signals in the GDB manual. The nostop argument could be useful in this situation, too.
Is there a way to exit from gdb connnection without stopping / exiting running program ? I need that running program continues after gdb connection closed.
Is there a way to exit from gdb connnection without stopping / exiting running program ?
(gdb) help detach
Detach a process or file previously attached.
If a process, it is no longer traced, and it continues its execution. If
you were debugging a file, the file is closed and gdb no longer accesses it.
List of detach subcommands:
detach checkpoint -- Detach from a checkpoint (experimental)
detach inferiors -- Detach from inferior ID (or list of IDS)
Type "help detach" followed by detach subcommand name for full documentation.
Type "apropos word" to search for commands related to "word".
Command name abbreviations are allowed if unambiguous.
Since the accepted (only other) answer does not specifically address how to shut down gdb without stopping the program under test, I'm throwing my hat into the ring.
Option 1
Kill the server from the terminal in which it's running by holding Ctrl+c.
Option 2
Kill the gdb server and/or client from another terminal session.
$ ps -u username | grep gdb
667511 pts/6 00:00:00 gdbserver
667587 pts/7 00:00:00 gdbclient
$ kill 667587
$ kill 667511
These options are for a Linux environment. A similar approach (killing the process) would probably also work in Windows.
am respawning the /bin/bash on ttyS1 port.ttyS0 is my console.
inittab entry is given below.
::respawn:/bin/bash < /dev/ttyS1 > /dev/ttyS1 2> /dev/ttyS1
My question is how to disable/kill respwning so that i can use serial port
for other application.
You can kill that bash process like other processes. However, init respawns it immediately - nothing gained.
To disable the process you have to edit /etc/inittab and comment out that line.
To inform init about this change you have to send a SIGHUP to init: kill -HUP pid-of-init.
(I think that pid-of-init is always 1).
If you need your bash connected to ttyS1 in some circumstances you may want to specify certain runlevels in which init should start bash.
Hope this answer helps... (see man inittab for further information)
On my Ubuntu this is what worked for me:
sudo rm -f /etc/init/<proc_name>.conf
sudo initctl stop <proc_name>
It returned a message:
initctl: Method "Get" with signature "ss" on interface "org.freedesktop.DBus.Properties" doesn't exist
but the process was stopped anyway without respawning.
inittab have to be reexamine otherwise it will launch the process.
Delete the command line link to process on /etc/inittab and execute:
# init q
or
# telinit q
Then , you can kill the process and it will not respawn.
I have a process that is already running for a long time and don't want to end it.
How do I put it under nohup (that is, how do I cause it to continue running even if I close the terminal?)
Using the Job Control of bash to send the process into the background:
Ctrl+Z to stop (pause) the program and get back to the shell.
bg to run it in the background.
disown -h [job-spec] where [job-spec] is the job number (like %1 for the first running job; find about your number with the jobs command) so that the job isn't killed when the terminal closes.
Suppose for some reason Ctrl+Z is also not working, go to another terminal, find the process id (using ps) and run:
kill -SIGSTOP PID
kill -SIGCONT PID
SIGSTOP will suspend the process and SIGCONT will resume the process, in background. So now, closing both your terminals won't stop your process.
The command to separate a running job from the shell ( = makes it nohup) is disown and a basic shell-command.
From bash-manpage (man bash):
disown [-ar] [-h] [jobspec ...]
Without options, each jobspec is removed from the table of active jobs. If the -h option is given, each jobspec is not
removed from the table, but is marked so that SIGHUP is not sent to the job if the shell receives a SIGHUP. If no jobspec is
present, and neither the -a nor the -r option is supplied, the current job is used. If no jobspec is supplied, the -a option
means to remove or mark all jobs; the -r option without a jobspec argument restricts operation to running jobs. The return
value is 0 unless a jobspec does not specify a valid job.
That means, that a simple
disown -a
will remove all jobs from the job-table and makes them nohup
These are good answers above, I just wanted to add a clarification:
You can't disown a pid or process, you disown a job, and that is an important distinction.
A job is something that is a notion of a process that is attached to a shell, therefore you have to throw the job into the background (not suspend it) and then disown it.
Issue:
% jobs
[1] running java
[2] suspended vi
% disown %1
See http://www.quantprinciple.com/invest/index.php/docs/tipsandtricks/unix/jobcontrol/
for a more detailed discussion of Unix Job Control.
Unfortunately disown is specific to bash and not available in all shells.
Certain flavours of Unix (e.g. AIX and Solaris) have an option on the nohup command itself which can be applied to a running process:
nohup -p pid
See http://en.wikipedia.org/wiki/Nohup
Node's answer is really great, but it left open the question how can get stdout and stderr redirected. I found a solution on Unix & Linux, but it is also not complete. I would like to merge these two solutions. Here it is:
For my test I made a small bash script called loop.sh, which prints the pid of itself with a minute sleep in an infinite loop.
$./loop.sh
Now get the PID of this process somehow. Usually ps -C loop.sh is good enough, but it is printed in my case.
Now we can switch to another terminal (or press ^Z and in the same terminal). Now gdb should be attached to this process.
$ gdb -p <PID>
This stops the script (if running). Its state can be checked by ps -f <PID>, where the STAT field is 'T+' (or in case of ^Z 'T'), which means (man ps(1))
T Stopped, either by a job control signal or because it is being traced
+ is in the foreground process group
(gdb) call close(1)
$1 = 0
Close(1) returns zero on success.
(gdb) call open("loop.out", 01102, 0600)
$6 = 1
Open(1) returns the new file descriptor if successful.
This open is equal with open(path, O_TRUNC|O_CREAT|O_RDWR, S_IRUSR|S_IWUSR).
Instead of O_RDWR O_WRONLY could be applied, but /usr/sbin/lsof says 'u' for all std* file handlers (FD column), which is O_RDWR.
I checked the values in /usr/include/bits/fcntl.h header file.
The output file could be opened with O_APPEND, as nohup would do, but this is not suggested by man open(2), because of possible NFS problems.
If we get -1 as a return value, then call perror("") prints the error message. If we need the errno, use p errno gdb comand.
Now we can check the newly redirected file. /usr/sbin/lsof -p <PID> prints:
loop.sh <PID> truey 1u REG 0,26 0 15008411 /home/truey/loop.out
If we want, we can redirect stderr to another file, if we want to using call close(2) and call open(...) again using a different file name.
Now the attached bash has to be released and we can quit gdb:
(gdb) detach
Detaching from program: /bin/bash, process <PID>
(gdb) q
If the script was stopped by gdb from an other terminal it continues to run. We can switch back to loop.sh's terminal. Now it does not write anything to the screen, but running and writing into the file. We have to put it into the background. So press ^Z.
^Z
[1]+ Stopped ./loop.sh
(Now we are in the same state as if ^Z was pressed at the beginning.)
Now we can check the state of the job:
$ ps -f 24522
UID PID PPID C STIME TTY STAT TIME CMD
<UID> <PID><PPID> 0 11:16 pts/36 S 0:00 /bin/bash ./loop.sh
$ jobs
[1]+ Stopped ./loop.sh
So process should be running in the background and detached from the terminal. The number in the jobs command's output in square brackets identifies the job inside bash. We can use in the following built in bash commands applying a '%' sign before the job number :
$ bg %1
[1]+ ./loop.sh &
$ disown -h %1
$ ps -f <PID>
UID PID PPID C STIME TTY STAT TIME CMD
<UID> <PID><PPID> 0 11:16 pts/36 S 0:00 /bin/bash ./loop.sh
And now we can quit from the calling bash. The process continues running in the background. If we quit its PPID become 1 (init(1) process) and the control terminal become unknown.
$ ps -f <PID>
UID PID PPID C STIME TTY STAT TIME CMD
<UID> <PID> 1 0 11:16 ? S 0:00 /bin/bash ./loop.sh
$ /usr/bin/lsof -p <PID>
...
loop.sh <PID> truey 0u CHR 136,36 38 /dev/pts/36 (deleted)
loop.sh <PID> truey 1u REG 0,26 1127 15008411 /home/truey/loop.out
loop.sh <PID> truey 2u CHR 136,36 38 /dev/pts/36 (deleted)
COMMENT
The gdb stuff can be automatized creating a file (e.g. loop.gdb) containing the commands and run gdb -q -x loop.gdb -p <PID>. My loop.gdb looks like this:
call close(1)
call open("loop.out", 01102, 0600)
# call close(2)
# call open("loop.err", 01102, 0600)
detach
quit
Or one can use the following one liner instead:
gdb -q -ex 'call close(1)' -ex 'call open("loop.out", 01102, 0600)' -ex detach -ex quit -p <PID>
I hope this is a fairly complete description of the solution.
Simple and easiest steps
Ctrl + Z ----------> Suspends the process
bg --------------> Resumes and runs background
disown %1 -------------> required only if you need to detach from the terminal
To send running process to nohup (http://en.wikipedia.org/wiki/Nohup)
nohup -p pid , it did not worked for me
Then I tried the following commands and it worked very fine
Run some SOMECOMMAND,
say /usr/bin/python /vol/scripts/python_scripts/retention_all_properties.py 1.
Ctrl+Z to stop (pause) the program and get back to the shell.
bg to run it in the background.
disown -h so that the process isn't killed when the terminal closes.
Type exit to get out of the shell because now you're good to go as the operation will run in the background in its own process, so it's not tied to a shell.
This process is the equivalent of running nohup SOMECOMMAND.
ctrl + z - this will pause the job (not going to cancel!)
bg - this will put the job in background and return in running process
disown -a - this will cut all the attachment with job (so you can close the terminal and it will still run)
These simple steps will allow you to close the terminal while keeping process running.
It wont put on nohup (based on my understanding of your question, you don't need it here).
On my AIX system, I tried
nohup -p processid>
This worked well. It continued to run my process even after closing terminal windows. We have ksh as default shell so the bg and disown commands didn't work.