I write some code as below with c++17 msvc:
#include <filesystem>
#include <iostream>
int main()
{
using namespace std::filesystem;
std::wstring s = L"c:\\windows\\system32\\applicationframehost.exe";
path p(s);
std::cout << absolute(p) << std::endl;
std::cout << exists(p) << std::endl;
std::cin.get();
return 0;
}
and run it on windows 10.
the application prints 0 -> means that file does not exist.
But it really exists and when I try with Cygwin ls -l command, it shows a good result:
#myuser> ls -l c:\windows\system32\applicationframehost.exe
-rwxr-xr-x 2 cody.nguyen 1049089 69800 Apr 12 2018 'c:\windows\system32\applicationframehost.exe'
Could you please explain me why and how to solve this issue from code?
thanks,
P/S: the function exists(p) works perfectly with almost other files except some in C:\Windows\System32\. I just tried to run my application with admin/system/user rights but got same results.
With ls -l command I just run it with user privilege only.
Related
I am working on Windows and I am trying to write an array into a Ubuntu device using C++ in Visual Studio 2019. Here's a sample of my code:
int Run_WriteCalibTable(char *pcIPAddress, int iNumArgs, float *fArgs, int *iAnsSize, char *sAns)
...
...
...
char pcFolderName[256];
char pcFileName[256];
sprintf(pcFolderName, "%s\\%s",pcSavePath, pcUUTSerialNumber);
sprintf(pcFileName, "%s\\calib_rfclock.conf",pcFolderName);
// WRITE TABLE ON PC
FILE *pFileW;
pFileW = fopen(pcFileName,"wb");
fwrite(&CalibTable, sizeof(char), CalibTable.hdr.v1.u32Len, pFileW);
fclose(pFileW);
}
return 0;
However, I keep having this pop-up from Microsoft Visual C++ Debug Library that says:
Debug Assertion Failed:
Program:...
File: f:\dd\vctools\crt_bld\sefl_x86\crt\src\fwrite.c
Line: 77
Expression: (stream != NULL)
...
I found this thread and I tried logging in as root on my Ubuntu device. I also tried:
mount -o remount,rw /path/to/parent/directory
chmod 777 /path/to/parent/directory
And I can also create/edit manualy any file in the directory I'm trying to write into with my code, but I get the same error when running it.
Anyone knows what could cause this? I think it could be on the Windows side, but I don't know what I am doing wrong. Thanks a lot in advance.
You never check that opening the file succeeds - and it most likely fails, which is why you get the debug pop-up. Your use of \ as directory delimiters may be the only reason why it fails, but you should check to be sure.
I suggest that you use std::filesystem::path (C++17) to build your paths. That makes it easy to create paths in a portable way. You could also make use of a C++ standard std::ofstream to create the file. That way you don't need to close it afterwards. It closes automatically when it goes out of scope.
Example:
#include <cerrno>
#include <cstring>
#include <filesystem>
#include <fstream>
int Run_WriteCalibTable(char *pcIPAddress, int iNumArgs, float *fArgs,
int *iAnsSize, char *sAns)
{
...
// Build std::filesystem::paths:
auto pcFolderName = std::filesystem::path(pcSavePath) / pcUUTSerialNumber;
auto pcFileName = pcFolderName / "calib_rfclock.conf";
// only try to write to the file if opening the file succeeds:
if(std::ofstream pFileW(pcFileName, std::ios::binary); pFileW) {
// Successfully opened the file, now write to it:
pFileW.write(reinterpret_cast<const char*>(&CalibTable),
CalibTable.hdr.v1.u32Len);
} else {
// Opening the file failed, print the reason:
std::cerr << pcFileName << ": " << std::strerror(errno) << std::endl;
}
...
}
I am running a beaglebone and want to write a program to sample the ADC. I am trying to use the blacklib (http://blacklib.yigityuce.com/index.html) from here. I cloned the git:
https://github.com/yigityuce/BlackLib
and tried to compile the example with
g++ exampleAndTiming.cpp -std=c++11
This however gives me a ton of errors like these:
In file included from exampleAndTiming.cpp:33:0:
exampleAndTiming/exampleAndTiming_GPIO.h: In function 'void exampleAndTiming_GPIO()':
exampleAndTiming/exampleAndTiming_GPIO.h:97:12: error: 'sleep' was not declared in this scope
sleep(1);
^
In file included from exampleAndTiming.cpp:34:0:
exampleAndTiming/exampleAndTiming_ADC.h: In function 'void exampleAndTiming_ADC()':
exampleAndTiming/exampleAndTiming_ADC.h:67:16: error: 'usleep' was not declared in this scope
usleep(1000);
^
so I include unistd.h (in exampleAndTiming.cpp), but then I get errors like these:
/tmp/ccbgiXE9.o: In function `exampleAndTiming_GPIO()':
exampleAndTiming.cpp:(.text+0x50): undefined reference to `Timing::startMeasure(std::string)'
exampleAndTiming.cpp:(.text+0x80): undefined reference to `BlackLib::BlackGPIO::BlackGPIO(BlackLib::gpioName, BlackLib::direction, BlackLib::workingMode)'
exampleAndTiming.cpp:(.text+0xbc): undefined reference to `Timing::endMeasure(std::string)'
exampleAndTiming.cpp:(.text+0xec): undefined reference to `BlackLib::BlackGPIO::BlackGPIO(BlackLib::gpioName, BlackLib::direction, BlackLib::workingMode)'
exampleAndTiming.cpp:(.text+0x104): undefined reference to `BlackLib::BlackGPIO::BlackGPIO(BlackLib::gpioName, BlackLib::direction, BlackLib::workingMode)'
exampleAndTiming.cpp:(.text+0x11c): undefined reference to `BlackLib::BlackGPIO::BlackGPIO(BlackLib::gpioName, BlackLib::direction, BlackLib::workingMode)'
exampleAndTiming.cpp:(.text+0x158): undefined reference to `Timing::startMeasure(std::string)'
I've been looking at some library examples and compiling it, but I cannot make sense of it all. I've compiled plenty of c++ and c programs before, but I can't get this one to work. So any help will be appreciated.
COMPLETE GUIDE how to compile BLACKLIB directly on BEAGLEBONE BLACK (rev C) running ANGSTROM:
Programs:
Putty - to communicate with BBB from Windows (using SSH with USB cable)
WinSCP - to manage (upload, create, delete) files directly on BBB
Code::Blocks - to write C++ programs
optionally
Termite 2.9 - to send and receive UART transmission from UART<->USB converter (actually Putty could be used to do that as well)
1) get the BlackLib from official site
2) unzip the library and copy following files into separate folder :
BlackADC.cpp, BlackADC.h, BlackCore.cpp, BlackCore.h, BlackDef.h, BlackErr.h, BlackGPIO.cpp, BlackGPIO.h, BlackI2C.cpp, BlackI2C.h, BlackLib.h, BlackPWM.cpp, BlackPWM.h, BlackSPI.cpp, BlackSPI.h, BlackUART.cpp, BlackUART.h
3) open following files in Code::Blocks BlackUART.cpp, BlackSPI.cpp, BlackI2C.cpp and add
#include <unistd.h>
right after #include "BlackUART.h", the "unistd.h" includes all the functions like sleep(), open(), close(), ... that otherwise seems missing
4) create your own program main.cpp, you may use the following code for testing UART1 and UART2:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sstream>
#include <string>
#include <iostream>
#include "BlackLib.h"
int main(){
std::string writeToUart1;
std::string writeToUart2;
std::string readFromUart1;
std::string readFromUart2;
int counter;
std::ostringstream os1;
std::ostringstream os2;
BlackLib::BlackUART Uart1(BlackLib::UART1,
BlackLib::Baud9600,
BlackLib::ParityEven,
BlackLib::StopOne,
BlackLib::Char8 );
// Pins on BeagleBone Black REV C
// UART1_RX -> GPIO_15 (P9.24)
// UART1_RX -> GPIO_14 (P9.26)
BlackLib::BlackUART Uart2(BlackLib::UART2,
BlackLib::Baud9600,
BlackLib::ParityEven,
BlackLib::StopOne,
BlackLib::Char8 );
// Pins on BeagleBone Black REV C
// UART2_RX -> GPIO_2 (P9.22)
// UART2_RX -> GPIO_3 (P9.21)
std::cout << "Program UART start" << std::endl << std::flush;
Uart1.open( BlackLib::ReadWrite | BlackLib::NonBlock );
Uart2.open( BlackLib::ReadWrite | BlackLib::NonBlock );
counter = 0;
while (true){
os1.str("");
os1.clear();
os1 << "Uart1 to TX: " << counter << "\n";
writeToUart1 = os1.str();
Uart1 << writeToUart1;
readFromUart1 = "";
Uart1 >> readFromUart1;
if (readFromUart1.compare("") != 0){
std::cout << "Uart1 from RX: " << readFromUart1 << "\n" << std::flush;
}
Uart1.flush( BlackLib::bothDirection );
counter++;
sleep(2);
os2.str("");
os2.clear();
os2 << "Uart2 to TX: " << counter << "\n";
writeToUart2 = os2.str();
Uart2 << writeToUart2;
readFromUart2 = "";
Uart2 >> readFromUart2;
if (readFromUart2.compare("") != 0){
std::cout << "Uart2 from RX: " << readFromUart2 << "\n" << std::flush;
}
Uart2.flush( BlackLib::bothDirection );
counter++;
sleep(2);
}
return 1;
}
5) save the main.cpp to the same folder as the BlackLib files
6) using WinSCP, create directory on the BBB (e.g. /home/uart) and copy all the BlackLib files and main.cpp into this folder
7) open Putty and navigate to the folder by :
cd /home/uart
8) compile the files by using :
gcc *.cpp -o main -std=c++11
9) run the program :
./main
10) connect the wires to UART<->USB converter and BBB. The ouput from BBB should look like :
Uart2 to TX: 1 OR Uart1 to TX: 0
Uart2 to TX: 3 OR Uart1 to TX: 2
depending on connection of wires
It seems I managed to fix it myself, some nooblike behaviour not including all the cpp files, but even more, I also needed to add #include to BlackCore.h to avoid tons of undefined function errors.
final command:
g++ exampleAndTiming.cpp exampleAndTiming/Timing.cpp BlackADC.cpp BlackCore.cpp BlackGPIO.cpp BlackI2C.cpp BlackPWM.cpp BlackSPI.cpp BlackUART.cpp -std=c++11
I'd probably need to make a makefile to compile the library seperately, time to do some more digging and learning.
I am the creator of BlackLib, Yiğit YÜCE. You found your answer by yourself. The makefile which you mentioned on your comment will be published shortly.
I just tried setting up curl for the first time using windows + mingw + eclipse juno + curl 7.29. I managed to get it to compile and build fine. I've added the two flags for lcurl and lcurldll.
For some reason though the following does not work:
#include <iostream>
#include <curl.h>
using namespace std;
int main(int argc,char *argv[]) {
cout << "L1" << endl;
CURL *curl;
curl = curl_easy_init();
cout << "L2" << endl;
}
Neither L1 nor L2 will print. If I comment out the easy_init line though it runs fine.
I can't seem to find any similar posts, sorry if this is a dupe. Also, I can't step into anything as it dies as soon as I hit run. I'm sure its something obvious.
Thanks in advance.
Eclipse IDE for C/C++ Developers Version: Juno Service Release 1
Build id: 20120920-0800
curl version: 7.29.0 - SSL enabled
URL: http://curl.haxx.se/gknw.net/7.29.0/dist-w32/curl-7.29.0-devel-mingw32.zip
as for mingw not sure which version I have, I just went to http://sourceforge.net/projects/mingw/files/ and downloaded / installed the latest ver.
In eclipse, under MinGW C++ linker, I have curl and curldll for libraries. In misc I have the static flag - those are the only compiler settings I have changed.
It does work for me, but i just had to add system("PAUSE") at the end since the console close before i can see anything.
here's my code :
#include <curl.h>
#include <iostream>
using namespace std;
int main(void)
{
cout << "L1" << endl;
CURL *curl;
curl = curl_easy_init();
cout << "L2" << endl;
system("PAUSE");
return 0;
}
If you get the message "cannot open include file: 'curl.h': no such file or directory" or something like that, this is because you've missed something in the installation of curl.
It took me a long time to install it.
My program (C++ on Solaris 10) writes output via wcout to its terminal when it is started from a shell. But when I execute it from within Sun Studio or the file manager is does not have a terminal and the ouput appears in the Sun Studio output window or nowhere at all.
I would like it to open its own terminal window in any of the three cases and attach wcout to this terminal window. I want this to be done be the program itself with C++ system calls not by the way how the program is executed from some shell or script. Because then execution in the Studio IDE and double-click in the file manager would still have the same effect.
Being a Windows programmer that seems quite natural to me but I could not find out how this is done in my Unix books nor in the web. Am I requesting the wrong thing, is it really so hard to do or am I missing something?
The following is close to what you want. It still has a few bugs:
The xterm cannot be normally closed (it closes when the program terminates, though). I have no idea why this is so.
Before the intended output, a number is output. Again, I have no idea why.
I don't seem to be able to redirect input.
Maybe someone else know how to fix those bugs (and any others I might not have noticed).
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <iostream>
#include <sstream>
int main()
{
int pt = posix_openpt(O_RDWR);
if (pt == -1)
{
std::cerr << "Could not open pseudo terminal.\n";
return EXIT_FAILURE;
}
char* ptname = ptsname(pt);
if (!ptname)
{
std::cerr << "Could not get pseudo terminal device name.\n";
close(pt);
return EXIT_FAILURE;
}
if (unlockpt(pt) == -1)
{
std::cerr << "Could not get pseudo terminal device name.\n";
close(pt);
return EXIT_FAILURE;
}
std::ostringstream oss;
oss << "xterm -S" << (strrchr(ptname, '/')+1) << "/" << pt << " &";
system(oss.str().c_str());
int xterm_fd = open(ptname,O_RDWR);
char c;
do read(xterm_fd, &c, 1); while (c!='\n');
if (dup2(pt, 1) <0)
{
std::cerr << "Could not redirect standard output.\n";
close(pt);
return EXIT_FAILURE;
}
if (dup2(pt, 2) <0)
{
std::cerr << "Could not redirect standard error output.\n";
close(pt);
return EXIT_FAILURE;
}
std::cout << "This should appear on the xterm." << std::endl;
std::cerr << "So should this.\n";
std::cin.ignore(1);
close(pt);
return EXIT_SUCCESS;
}
You want to output to a file (redirect, using a logging API or close stdout/reopen it as a file). And then tail it with tail -f in a terminal of your choice.
This has added benefit of saving your log output for review even if the terminal crashes/is killed.
When you invoke your program, instead of running: myprog 1 2 3 a b c, run xterm -e myprog 1 2 3 a b c.
I would recommnend to create a shell script that runs the terminal to which you pass your program to execute, then you should call that script instead of your program from the file manager.
Your script.sh:
#!/bin/sh
xterm -e /path_to_your_program/your_program
Using mknod to create pipe in /tmp every linux have /tmp and everyone always allowed to use it
system("mknod /tmp/printing_pipe pipe");
system("qterminal -e tail -f /tmp/printing_pipe");
write to the /tmp/printing_pipe to use it
I have an Isilon NAS in 10.20.30.11 for example, and I mounted it like following:
mount 10.20.30.11:/folder /content
I could use ls command to find the file in folder or /content. Its mod is 777.
bash-3.00# ls -l /content/a/b/1.txt
total 344131
rwxrwxrwx 1 1005 65533 140750 Feb 28 00:58 1.txt
But I cannot access it by access() function.
#include <iostream>
#include <string>
#include <unistd.h>
#include <cerrno>
using namespace std;
#include <stdio.h>
int main( int argc, const char* argv[] )
{
int returnVal = 0;
returnVal = access(argv[1], R_OK);
cout << returnVal << endl;
cout << errno << endl;
return 0;
}
It will return -1 and 2 as a result, which means 'No such file or directory'.
./a.out /content/a/b/1.txt
-1
2
#define ENOENT 2 /* No such file or directory */
It is not a permission problem I think, because the mod is 777, and the result is 'No such file or directory'.
From the Linux man pages.
access() may not work correctly on NFS
file systems with UID mapping enabled,
because UID mapping is done on the
server and hidden from the client,
which checks permissions.
Finally, it is found that it need to use following command to mount the Isilon storage.
mount -o vers=2,proto=tcp
1.2.3.4:/remote /mnt
The version and protocol need specified.
Thanks!