I have an executable, which has a few system commands (basically it does copying and running script files). When I test in standalone (launching the executable myself as with sudo) system() is working fine.
Now I integrate my executable with supervisord. Functionality of my executable is working fine, but the system() command fails with 255 / -1 (8 bit representation).
List of things I checked:
The current working directory of the process is correct
Supervisord and my process are running as root
chown of directory and file are root
Any other suggestions?
system("sudo cp ./Scripts/x.sh /tmp/");
sudo is the command to obtain superuser rights. It normally promts you for password (but under some circumstances, it skips it). Maybe it fails if it has no console to prompt you.
Anyway you should NOT do this. You sould just write system("cp ./Scripts/x.sh /tmp/") and start your program with root access (supervisord probably has a way to do that).
Related
I installed flatpak using guix, but it segfaulted on startup. I wanted to debug it, but guix installs a wrapper script for flatpak, so I get this error when trying to run it under gdb:
"/home/user/.guix-profile/bin/flatpak": not in executable format: file format not recognized
and I tried to edit the wrapper script to call gdb, but this wrapper script is not even editable by root, because it is owned by root and has read-only permissions.
Simply copy the script to your current working directory:
cp /home/user/.guix-profile/bin/flatpak .
Mark it as writable:
chmod +w flatpak
Edit the script with your favourite text editor, to replace the string exec -a with exec gdb --args.
And finally, run it with any arguments you provided before, when it misbehaved:
./flatpak remote-add flathub https://flathub.org/repo/flathub.flatpakrepo
In this particular case, this wasn't immediately super-useful, because a debug symbol output hasn't been built for this package. But at least I could get a backtrace out of gdb.
I'm working on a Yocto based system. My problem is that I can't start my programm written in C++ and the webserver (node.js) at the same time right after the boot of my device.
I already tried this in /etc/init.d:
#! /bin/bash
/home/ProjectFolder/myProject
cd /home/myapp && DEBUG=myapp:* npm start
exit 0
I changed the rights after creating the script by
chmod +x ./startProg.sh
After that I linked it by
update-rc.d startProg.sh defaults
After reboot the system only starts the C++-programm. I tried some other possibilities like seperating the two comands in different shell-scripts, but that didn't work out any better.
Is there any option I missed or did I make any mistake trying to put those two processes into the autostart?
This of course isn't a C++ or Node.js question. A shell script is a list of commands that are executed in order, unless specified otherwise. So your shell script runs your two programs in the order specified, first myProject and when that's done npm will be started.
This is the same as what would happen from the prompt and the solution is the same: /home/ProjectFolder/myProject &
I am trying to have my program change directory (to where the user wishes to) but I am unable to navigate there and create a file? It appears that I am able to navigate there but when I get to the next system call it returns back to the current directory
Is there a way to set where my program cwd is pointing to?
std::string s1 = "cd " + userDirectory;
system(s1.c_str());
system("dir > test.txt");
SetCurrentDirectory Win32 on Windows.
chdir() / _chdir for POSIX (a common C API available on many OS:es).
boost/std::filesystem current_path() for C++ (std in C++17).
The system function starts a new command interpreter as a new process. And then runs the commands in that command interpreter. And as the cd command is a built-in command it will only apply to that command interpreter process, not your process.
You have a couple of solutions you can try:
Put the commands (cd and dir and everything else) in to a script file that you run.
Change the working directory of your process.
On Windows you can change working directory using SetCurrentDirectoryW function.
I successfully compiled a MUD source code, and it says in the instructions to start up the server using
nohup ./startup &
although when I do this it gives me this error:
$ nohup: ignoring input and appending output to `nohup.out'
nohup: failed to run command `./startup': Permission denied
I have looked all over the internet to find the answer. A few of them said to put my cygwin directory in the root folder (I am using windows 7) and its directory is C:\cygwin
so thats not a problem.. Can anyone help me with this please??
Try chmod +x startup, maybe your startup file is not executable.
From "man nohup":
If the standard output is a terminal, all output written by the named
utility to its standard output shall be appended to the end of the
file nohup.out in the current directory. If nohup.out cannot be
created or opened for appending, the output shall be appended to the
end of the file nohup.out in the directory specified by the HOME
environment variable. If neither file can be created or opened for
appending, utility shall not be invoked. If a file is created, the
file's permission bits shall be set to S_IRUSR | S_IWUSR.
My guess is that since "sh -c" doesn't start a login shell, it is inheriting the environment of the invoking shell, including the HOME environment variable, and is trying to open it there. So I would check the permissions of both your current directory and $HOME. You can try to touch test.txt in current directory or $HOME to see if you can perform that command.
As staticx writes, check the permissions of the directory (and the user) - and the executable.
Instead of using nohup:
check if nohup is needed at all, try ./startup </dev/null >mud.out 2>mud.err &, then close the terminal window and check if it is running
or just run ./startup in a screen session and detach it (<ctrl>+<a>,<d>)
I’ve produced a C++ program in Eclipse running on Redhat, which compiles and runs fine through Eclipse.
I thought that to run it separately to Eclipse you use the build artifact which is in the directory set via the project’s properties.
However this executable doesn’t run (I know it’s an executable as I’ve set it to be an executable via the project’s properties and it shows up as such via the ls command and the file explorer).
When attempting to run it using the executable’s name, I get the error:
bash: <filename>: command not found
When attempting to run it as a bash file:
<filename>: <filename>: cannot execute binary file
And when running it with "./" before the file name, nothing happens. Nothing new appears in the running processes and the terminal just goes to the next line as though I’d just pressed enter with no command.
Any help?
You've more or less figure out the first error yourself. when you just run <filename> , it is not in your PATH environment variable, so you get "command not found". You have to give a full or relative path when to the program in order to run it, even if you're in the same directory as the program - you run it with ./<filename>
When you do run your program, it appears to just exit as soon as you start it - we can't help much with that without knowing what the program does or see some code.
You can do some debugging, e.g. after the program just exits run echo $? to see if it exited with a particular exit value, or run your program using the strace tool to see what it does (or do it the usual way, insert printf debugging, or debug it with gdb)