I am trying to get system date in a C program on a MSVC++ 6.0 compiler. I am using a system call:
system("date /T") (output is e.g. 13-Oct-08 which is date on my system in the format i have set)
but this prints the date to the i/o console.
How do i make take this date as returned by above system call and store it as a string value to a string defined in my code?
Or
Is there any other API i can use to get the date in above mentioned format (13-Oct-08, or 13-10-08) ?
-AD
#include <windows.h>
#include <iostream>
int main() {
SYSTEMTIME systmDateTime = {};
::GetLocalTime(&systmDateTime);
wchar_t wszDate[64] = {};
int const result = ::GetDateFormatW(
LOCALE_USER_DEFAULT, DATE_SHORTDATE,
&systmDateTime, 0, wszDate, _countof(wszDate));
if (result) {
std::wcout << wszDate;
}
}
There are a couple of ways to do this using API functions, two that jump to mind are strftime and GetDateFormat.
I'd like to provide examples but I'm afraid I don't have a Win32 compiler handy at the moment. Hopefully the examples in the above documentation are sufficient.
Have a read of Win32 Time functions; GetLocalTime may be your friend. There are also the standard C time functions, time and strftime.
For future reference, in a C program, it is almost always the wrong answer to invoke an external utility and capture it's STDOUT.
Thanks for the pointers.
I used this and it served my purpose:
#include <time.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/timeb.h>
#include <string.h>
int main()
{
char tmpbuf[128];
time_t ltime;
struct tm *today;
_strdate( tmpbuf );
printf("\n before formatting date is %s",tmpbuf);
time(<ime);
today = localtime( <ime );
strftime(tmpbuf,128,"%d-%m-%y",today);
printf( "\nafter formatting date is %s\n", tmpbuf );
}
-AD
Related
I tried a example on Auto for variable initialization and STL in C++. For normal variable, type was printed using : typeid(var_name).name() to print i (integer) / d(float) / pi(pointer) which works fine.
But while working on STL,
`#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<string> st;
st.push_back("geeks");
st.push_back("for");
for (auto it = st.begin(); it != st.end(); it++)
cout << typeid(it).name() << "\n";
return 0;
}
`
which gives output like,
`N9__gnu_cxx17__normal_iteratorIPNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEESt6vectorIS6_SaIS6_EEEE
N9__gnu_cxx17__normal_iteratorIPNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEESt6vectorIS6_SaIS6_EEEE`
and I am unable to understand the output logic behind it, can anyone explain why it is giving output like this? and thanks in advance
That's the "name mangled" version of the name of the type of it. typeinfo::name() is not required by the standard to return a name in human-readable format (a shortcoming IMHO) and GCC doesn't do so.
To get the actual, human-readable name, you need to call the abi::__cxa_demangle() function provided by GCC, but note that this is non-portable so if your project needs to work on different compilers you'll need to wrap it appropriately.
I am using an std::chrono::system_clock::time_point in my program.
When the application stops I want to save to the time_point to a file and load it again when the application starts.
If it was an UNIX-Timestamp I could simply store the value as integer. Is there a way to similarly store a time_point?
Yes. Choose the precision you desire the timestamp in (seconds, milliseconds, ... nanoseconds). Then cast the system_clock::time_point to that precision, extract its numeric value, and print it:
cout << time_point_cast<seconds>(system_clock::now()).time_since_epoch().count();
Though not specified by the standard, the above line (de facto) portably outputs the number of non-leap seconds since 1970-01-01 00:00:00 UTC. That is, this is a UNIX-Timestamp.
I am attempting to get the above code blessed by the standard to do what it in fact does by all implementations today. And I have the unofficial assurance of the std::chrono implementors, that they will not change their system_clock epochs in the meantime.
Here's a complete roundtrip example:
#include <chrono>
#include <iostream>
#include <sstream>
int
main()
{
using namespace std;
using namespace std::chrono;
stringstream io;
io << time_point_cast<seconds>(system_clock::now()).time_since_epoch().count();
int64_t i;
system_clock::time_point tp;
io >> i;
if (!io.fail())
tp = system_clock::time_point{seconds{i}};
}
I would like to use PAPI to get the overall counters of all C++11 std::thread threads in a program.
PAPI documentation on Threads says that:
Thread support in the PAPI library can be initialized by calling the following low-level function in C: int PAPI_thread_init(unsigned long(*handle)(void));
where the handle is a
Pointer to a routine that returns the current thread ID as an unsigned long.
For example, for pthreads the handle is pthread_self.
But, I have no idea what it should be with C++11 std::thread.
Nor if it makes more sense to use something different from PAPI.
C++11 threading support has the std::this_thread::get_id() function that returns a std::thread::id instance which can be serialized to a stream. Then you coud try to read an unsigned long from the stream and return ir. Something like this:
#include <thread>
#include <iostream>
#include <sstream>
unsigned long current_thread_id()
{
std::stringstream id_stream;
id_stream << std::this_thread::get_id();
unsigned long id;
id_stream >> id;
return id;
}
int main(int argc, char** argv)
{
std::cout << current_thread_id();
return 0;
}
So in this snippet the current_thread_id function is what you are looking for, but you should add proper error handling (the thread id may not always be a number, in that case you will not be able to read a number from the stream and you should handle that accordingly).
That being said, maybe just use GetCurrentThreadId , since you are already introducing the Linux specific pthread_self.
I'm going for absolute minimalism here. (It's been a while since I've worked with the Lua C API.)
#include <lua.hpp>
#include <iostream>
#include <string>
using namespace std;
int main(int argc, char** argv)
{
lua_State* state = luaL_newstate();
luaL_openlibs(state);
string input;
while (getline(cin, input))
{
auto error = luaL_dostring(state, input.c_str());
if (error)
{
cerr << "Lua Error: " << lua_tostring(state, -1) << '\n';
lua_pop(state, 1);
}
}
lua_close(state);
return 0;
}
This program works fine as long as I feed it perfect Lua. However, if I enter something bad (such as asdf()), the program crashes! Why is it not handling my error gracefully?
I've tried breaking out the calls before. It crashes on the call to lua_pcall itself. I never make it past that line.
The binary download (5.2.1 I believe) has a bug that was corrected in 5.2.3. I rebuilt the library from source, and now my program works fine.
I have one application which reads user default locale in Windows Vista and above. When i tried calling the API for getting User default Locale API is crashing. Below is the code, It will be helpfull if any points the reason
#include <iostream>
#include <WinNls.h>
#include <Windows.h>
int main()
{
LPWSTR lpLocaleName=NULL;
cout << "Calling GetUserDefaultLocaleName";
int ret = GetUserDefaultLocaleName(lpLocaleName, LOCALE_NAME_MAX_LENGTH);
cout << lpLocaleName<<endl;
}
You need to have lpLocaleName initialized to a buffer prior to calling the API. As a general consensus, if an API has a LPWSTR data type parameter, call malloc or new on it first, to the desired length, in this case, LOCALE_NAME_MAX_LENGTH. Setting it to NULL and passing it to the API function is a guaranteed way to crash!
Hope this helps,
Best regards,
Tom.
In addition to the previous answers, you should also be aware that you can't print a wide string with cout; instead, you should use wcout.
So:
#include <iostream>
#include <WinNls.h>
#include <Windows.h>
#define ARRSIZE(arr) (sizeof(arr)/sizeof(*(arr)))
using namespace std;
int main()
{
WCHAR_T localeName[LOCALE_NAME_MAX_LENGTH]={0};
cout<<"Calling GetUserDefaultLocaleName";
int ret = GetUserDefaultLocaleName(localeName,ARRSIZE(localeName));
if(ret==0)
cout<<"Cannot retrieve the default locale name."<<endl;
else
wcout<<localeName<<endl;
return 0;
}
I believe you need to initialise lpLocaleName to an empty string of 256 chars (for example) then pass the length (256) where you have LOCALE_NAME_MAX_LENGTH