I'm trying to run my application as root because I need to access low level hardware on my computer.
When I run the command:
./application_name
...it works, except gives an error that it needs root. However, when I run this:
sudo ./application_name
...I get no terminal ouput.
I've tested that every time that I run an executable on Linux as root, it doesn't print anything to terminal. How can I fix this?
Edit: somewhat of a test case provided (mobile so can't type out much):
sudo g++ test.cpp -o executable
sudo chmod +x executable
This works on Debian:
./executable
This doesn't:
sudo ./executable
test.cpp:
#include <iostream>
int main() {
std::cout << "Hello World!";
}
That behavior is really strange. Root permissions for that application should have no effect on std output.
For example, I made a simple test, a "hello world" that I ran as root on Debian OS and I had output in terminal.
A simple test to convince yourself that you should have the output, is to make a redirect to a file. For example sudo ./executable > output.txt and you'll see that everything should be OK.
Note that it should be strange if you don't have output from a simple "hello world".
Related
I am trying to grant reboot capability to my appimage using setcap. Using following command on a simple application (all it does is to reboot the machine) works, however it does not work with my actual app's appimage.
Both applications essentially do the same thing for rebooting:
sync();
if(reboot(RB_AUTOBOOT) == -1) {
// handle errno
}
(In case you want to try the code, include <unistd.h> and <sys/reboot.h>)
Output with minimal test app:
sudo setcap -v cap_sys_boot+ep ./main
./main: OK
Output with appimage:
sudo setcap -v cap_sys_boot+ep ./app.AppImage
./app.AppImage differs in [pe]
Any idea what can I do?
If I understand correctly, std::cout << "Test"; should output Test to the terminal emulator, but when I run a program using it, it instead creates a file called a.out. Is there a way to change this?
Try running the a.out file from inside a Terminal (if Linux/Mac) or cmd (if Windows) by running the following command:
./a.out
If it throws any permission exception in Linux/Mac then you should try running the following command first,
chmod +x ./a.out
and then run,
./a.out
Background
I created a simple Hello World C++ program:
#include <iostream>
using namespace std;
int main() {
cout << "Hello World!" << endl;
return 0;
}
And compiled it with clang++ like so (g++ points to clang++ on OS X apparently):
g++ helloworld-cpp.cpp
This produces an executable, a.out. Running it at the prompt causes bash to throw the error Operation not permitted, as shown:
$ ./a.out
-bash: ./a.out: Operation not permitted
Things I've Tried
Verifying the file has execute permissions, and no attributes or flags that would prevent it from running, using ls -leO:
-rwxr-xr-x 1 monarch staff - 15212 Jan 1 13:51 a.out
Disabling "System Integrity Protection" using csrutil disable from the Recovery OS terminal, rebooting, recompiling, and running a.out. The same error messages results.
Question
Are there any other restrictions that could prevent binaries I compile on Mac OS X from running?
Figured it out.
My code was on an encrypted sparseimage, which had the quarantined attribute set on it. I checked this by running mount like so (see attributes on /Volumes/work):
$ mount
/dev/disk0s2 on / (hfs, local, journaled)
/dev/disk2s2 on /Volumes/work (hfs, local, nodev, nosuid, journaled, noowners, quarantine, mounted by monarch)
The actual sparseimage is located in my home folder, titled work.sparseimage. I removed the quarantine attribute like so:
$ xattr -d com.apple.quarantine work_personal.sparseimage
I then unmounted (ejected) the image, then re-mounted it, recompiled the file and it executed without the error.
Special thanks to #Mark Setchell for asking me in the question's comments if noexec was set on the drive, and to everyone else for their suggestions.
I tried the following code, to communicate with the command line from c++ code.
#include<iostream>
#include<cv.h>
int main()
{
system("gnome-terminal");
system("cd");
}
The gnome-terminal command is executing fine. After I close the terminal, when am expecting the cd to execute, however, is not happening. Could you please help me and point out the reason? Thanks. I was expecting the function to make the cmd go down to the home directory
, but it did not. am working in linux
I tried it even by removing gnome. simple cd is not working. am I doing something rong>?
If I try ls, it seems to be working fine!
My main aim is to open a new terminal, and execute commands on that new terminal through the present program that opened the new terminal. Could you please tell me how I can achieve this??
If you want to run a program and wait for it to finish before executing next line, take a look at this page and example code here: http://www.thegeekstuff.com/2012/03/c-process-control-functions/
But if you want to run gnome-terminal and execute a command in newly created window, do this:
system("gnome-terminal -x sh -c 'cd /tmp ; ls -la'");
The system function creates a shell child process to execute the specified command.
cd is a shell command which changes the current working directory of that shell process only.
So the child's cd probably works fine, but it has no effect on your C++ program, which is a different process.
Instead, you probably want to look at the Linux system call chdir.
Thanks for your help!! This command worked perfectly fine from this link
https://superuser.com/questions/198015/open-gnome-terminal-programmatically-and-execute-commands-after-bashrc-was-execu
gnome-terminal -x sh -c 'command1; command2; exec bash'
and I entered the respective commands in the new window. But to change the working directory in the shell am working o, I haven't still figured that out.
I'm trying to run a Hello world C++ on Eclipse on Ubuntu 12.04. I installed g++ and wrote this code:
#include<vector>
#include<string>
#include <iostream>
using namespace std;
int main()
{
cout << "Hello World" << endl;
return 0;
}
Compile output:
**** Build of configuration Debug for project TopCoder ****
make all
make: Nothing to be done for `all'.
**** Build Finished ****
Run output message:
Launching TopCoder has encountered a problem
Error starting process
Error starting process.
Exec_tty error:Cannot run program "/media/01CCE00FA6888D80/Achieve/Eclipse/TopCoder/Debug/TopCoder": Unknown reason
Exec_tty error:Cannot run program "/media/01CCE00FA6888D80/Achieve/Eclipse/TopCoder/Debug/TopCoder": Unknown reason
Exec_tty error:Cannot run program "/media/01CCE00FA6888D80/Achieve/Eclipse/TopCoder/Debug/TopCoder": Unknown reason
when I put the source code on ext4 drive it builds and run
I changed
proc /proc proc nodev,noexec,nosuid 0 0
in /etc/fstab to
proc /proc proc dev,exec,suid 0 0
But no usefulness.
You're tring to run an application from the /media/01CCE00FA6888D80 volume. Removable USB? The most likely culprit is noexec as an option to the default mount command line.
check if noexec is part of the options for mounting the filesystem using:
grep noexec /proc/mounts
if this results in output indicating that noexec is in effect for the file system then try:
sudo mount -o remount,exec /media/01CCE00FA6888D80
Also, if the removable volume is NTFS, your milage may vary.
Try to build it from the command line. Then you will know if the problem is involved with g++ or with eclipse. I guess you should change your compiler path somewhere in the eclipse, are you sure you have eclipse-cdt? THe easiest way to compile it is:
g++ yourfile.cpp
Your problem is that you're workspace is probably on a different drive than the one you installed ubuntu on
You are running you project over Linux . i had facing same issue when my project was in my E drive . i gave read -write permission but still that was not enough for me . The same error was keep coming when i was trying to run the project .
I have shifted my project in my Home folder ,gave permission and the project ran !! .
I believe there was a problem with some permission for LINUX C compiler .