c++ time stamp to human readable datetime function

Question

i have simple function that i need to return human readable date time from timestamp but somehow it returns the same timestam in seconds:

input 1356953890

std::string UT::timeStampToHReadble(long  timestamp)
{
    const time_t rawtime = (const time_t)timestamp;

    struct tm * dt;
    char timestr[30];
    char buffer [30];

    dt = localtime(&rawtime);
    // use any strftime format spec here
    strftime(timestr, sizeof(timestr), "%m%d%H%M%y", dt);
    sprintf(buffer,"%s", timestr);
    std::string stdBuffer(buffer);
    return stdBuffer;
}

output 1231133812

this is how i call it :

long timestamp = 1356953890L ;
std::string hreadble = UT::timeStampToHReadble(timestamp);
std::cout << hreadble << std::endl;

and the output is : 1231133812 and i what it to be somekind of this format : 31/1/ 2012 11:38:10 what im missing here ?

UTDATE :
the solution strftime(timestr, sizeof(timestr), " %H:%M:%S %d/%m/%Y", dt);

Why do you have a temporary `buffer` and `stdBuffer` variables? The string created by `strftime` should be enough, and you should be able to just do `return timestr;`, or worst case `return std::string(timestr);`. — Some programmer dude, Jan 21 '13 at 10:22
@JoachimPileborg asked myself the same thing. Maybe he abused stringstream operator overload earlier ;-) — Najzero, Jan 21 '13 at 10:22
Can you show how you call this function, and display the result ? — Sander De Dycker, Jan 21 '13 at 10:54
Works for me: http://ideone.com/7K2gk3. I added 6 lines to your code to create a complete program that others can run. If you had done the same then you might have an answer by now. You're probably printing the wrong thing. — Steve Jessop, Jan 21 '13 at 11:02
i want it to be something like should be : 31/1/2012 11:38:10 — user63898, Jan 21 '13 at 11:14
Well then you need to put some `/` and `:` characters in your format string, `strftime` isn't magic, it can't read your mind. — Jonathan Wakely, Jan 21 '13 at 11:18
I find that somewhat hard to believe. `"%m"` will never output anything but a two digit number between `"01"` and `"12"`, for example; you claim it is outputting `"13"`. — James Kanze, Jan 21 '13 at 11:19
@JamesKanze since there are no delimiters it could be that %m is 1 and not 13 — AndersK, Jan 21 '13 at 11:26

ormurin · Answer 1 · 2014-10-09T08:18:59.287

10

It can be boiled down to:

std::string UT::timeStampToHReadble(const time_t rawtime)
{
    struct tm * dt;
    char buffer [30];
    dt = localtime(&rawtime);
    strftime(buffer, sizeof(buffer), "%m%d%H%M%y", dt);
    return std::string(buffer);
}

Changes:

I would prefer to do the casting outside the function. It would be weird to cast a time_t to a long before calling the function, if the caller had the time_t data.
It's not necessary to have two buffers (and therefore not necessary to copy with sprintf)

edited Oct 09 '14 at 08:18

answered Jan 23 '14 at 08:34

ormurin

358
3
11

1

Do you mean `strftime(buffer, sizeof(buffer), "%m%d%H%M%y", dt);` on that second to last line? – Frank Conry Mar 29 '14 at 05:11

c++ time stamp to human readable datetime function

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