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C / C ++: how to get integer unix timestamp of build time (not a string)

I'm trying to achieve is quite trivial things: I need to store the entire 32-bit timestamp unix build time, but all found macros are ( __DATE__, __TIME__, __TIMESTAMP__) to expand a line, rather than the whole.

It seems we just don’t (this is rather strange for me). I really want to have an integer, not a string.

What are the best methods to obtain it?

UPD:

As a side note: I am doing nested things, so I don’t have enough resources (say 128 Kbytes of flash memory), so this is a really bad idea for parsing a string.

Why do I need this: I just need to have a unique version number for each beta. Firstly, the hexadecimal file will be called as my-firmware-v2-33-BETA-1397315745.hex, and secondly, when I need to show the current version on the device’s screen, I would like to repeat it in a different format.

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7 answers

So tonight I had some fun and created a macro header file to create a UNIX timestamp, without any external program or special compiler function! Just include the header and use the macro __TIME_UNIX__.

Actually the code is pretty simple:

  • str[i]-'0', .
  • chux; ? :.
  • ? :.
  • , UNIX 4 .
  • , , UNIX. , SEC_PER_DAY , JAN 01 1970, 00:00:00 0.

ATMEL Studio 7 (Visual Studio 2015) (avr-gcc, -O1 optimization), .lss.

, . !

/*
 * compile_time.h
 *
 * Created: 30.05.2017 20:57:58
 *  Author: Dennis (instructable.com/member/nqtronix)
 *
 * This code provides the macro __TIME_UNIX__ which returns the current time in UNIX format. It can
 * be used to identify a version of code on an embedded device, to initialize its RTC and much more.
 * Along that several more constants for seconds, minutes, etc. are provided
 *
 * The macro is based on __TIME__ and __DATE__, which are assumed to be formatted "HH:MM:SS" and
 * "MMM DD YYYY", respectively. The actual value can be calculated by the C compiler at compile time
 * as all inputs are literals. MAKE SURE TO ENABLE OPTIMISATION!
 */ 


#ifndef COMPILE_TIME_H_
#define COMPILE_TIME_H_

// extracts 1..4 characters from a string and interprets it as a decimal value
#define CONV_STR2DEC_1(str, i)  (str[i]>'0'?str[i]-'0':0)
#define CONV_STR2DEC_2(str, i)  (CONV_STR2DEC_1(str, i)*10 + str[i+1]-'0')
#define CONV_STR2DEC_3(str, i)  (CONV_STR2DEC_2(str, i)*10 + str[i+2]-'0')
#define CONV_STR2DEC_4(str, i)  (CONV_STR2DEC_3(str, i)*10 + str[i+3]-'0')

// Some definitions for calculation
#define SEC_PER_MIN             60UL
#define SEC_PER_HOUR            3600UL
#define SEC_PER_DAY             86400UL
#define SEC_PER_YEAR            (SEC_PER_DAY*365)
#define UNIX_START_YEAR         1970UL

// Custom "glue logic" to convert the month name to a usable number
#define GET_MONTH(str, i)      (str[i]=='J' && str[i+1]=='a' && str[i+2]=='n' ? 1 :     \
                                str[i]=='F' && str[i+1]=='e' && str[i+2]=='b' ? 2 :     \
                                str[i]=='M' && str[i+1]=='a' && str[i+2]=='r' ? 3 :     \
                                str[i]=='A' && str[i+1]=='p' && str[i+2]=='r' ? 4 :     \
                                str[i]=='M' && str[i+1]=='a' && str[i+2]=='y' ? 5 :     \
                                str[i]=='J' && str[i+1]=='u' && str[i+2]=='n' ? 6 :     \
                                str[i]=='J' && str[i+1]=='u' && str[i+2]=='l' ? 7 :     \
                                str[i]=='A' && str[i+1]=='u' && str[i+2]=='g' ? 8 :     \
                                str[i]=='S' && str[i+1]=='e' && str[i+2]=='p' ? 9 :     \
                                str[i]=='O' && str[i+1]=='c' && str[i+2]=='t' ? 10 :    \
                                str[i]=='N' && str[i+1]=='o' && str[i+2]=='v' ? 11 :    \
                                str[i]=='D' && str[i+1]=='e' && str[i+2]=='c' ? 12 : 0)

#define GET_MONTH2DAYS(month)  ((month == 1 ? 0 : 31 +                      \
                                (month == 2 ? 0 : 28 +                      \
                                (month == 3 ? 0 : 31 +                      \
                                (month == 4 ? 0 : 30 +                      \
                                (month == 5 ? 0 : 31 +                      \
                                (month == 6 ? 0 : 30 +                      \
                                (month == 7 ? 0 : 31 +                      \
                                (month == 8 ? 0 : 31 +                      \
                                (month == 9 ? 0 : 30 +                      \
                                (month == 10 ? 0 : 31 +                     \
                                (month == 11 ? 0 : 30))))))))))))           \


#define GET_LEAP_DAYS           ((__TIME_YEARS__-1968)/4 - (__TIME_MONTH__ <=2 ? 1 : 0))



#define __TIME_SECONDS__        CONV_STR2DEC_2(__TIME__, 6)
#define __TIME_MINUTES__        CONV_STR2DEC_2(__TIME__, 3)
#define __TIME_HOURS__          CONV_STR2DEC_2(__TIME__, 0)
#define __TIME_DAYS__           CONV_STR2DEC_2(__DATE__, 4)
#define __TIME_MONTH__          GET_MONTH(__DATE__, 0)
#define __TIME_YEARS__          CONV_STR2DEC_4(__DATE__, 7)

#define __TIME_UNIX__         ((__TIME_YEARS__-UNIX_START_YEAR)*SEC_PER_YEAR+       \
                                GET_LEAP_DAYS*SEC_PER_DAY+                          \
                                GET_MONTH2DAYS(__TIME_MONTH__)*SEC_PER_DAY+         \
                                __TIME_DAYS__*SEC_PER_DAY-SEC_PER_DAY+              \
                                __TIME_HOURS__*SEC_PER_HOUR+                        \
                                __TIME_MINUTES__*SEC_PER_MIN+                       \
                                __TIME_SECONDS__)

#endif /* COMPILE_TIME_H_ */

Edit:

100 400 . 2001 2101 , :

/* 
 *
 * Created: 29.03.2018
 *
 * Authors:
 * 
 * Assembled from the code released on Stackoverflow by:
 *   Dennis (instructable.com/member/nqtronix)    |   https://stackoverflow.com/questions/23032002/c-c-how-to-get-integer-unix-timestamp-of-build-time-not-string
 * and
 *   Alexis Wilke                                 |   https://stackoverflow.com/questions/10538444/do-you-know-of-a-c-macro-to-compute-unix-time-and-date
 *
 * Assembled by Jean Rabault
 * 
 * UNIX_TIMESTAMP gives the UNIX timestamp (unsigned long integer of seconds since 1st Jan 1970) of compilation from macros using the compiler defined __TIME__ macro.
 * This should include Gregorian calendar leap days, in particular the 29ths of February, 100 and 400 years modulo leaps.
 * 
 * Careful: __TIME__ is the local time of the computer, NOT the UTC time in general!
 * 
 */

#ifndef COMPILE_TIME_H_
#define COMPILE_TIME_H_

// Some definitions for calculation
#define SEC_PER_MIN             60UL
#define SEC_PER_HOUR            3600UL
#define SEC_PER_DAY             86400UL
#define SEC_PER_YEAR            (SEC_PER_DAY*365)

// extracts 1..4 characters from a string and interprets it as a decimal value
#define CONV_STR2DEC_1(str, i)  (str[i]>'0'?str[i]-'0':0)
#define CONV_STR2DEC_2(str, i)  (CONV_STR2DEC_1(str, i)*10 + str[i+1]-'0')
#define CONV_STR2DEC_3(str, i)  (CONV_STR2DEC_2(str, i)*10 + str[i+2]-'0')
#define CONV_STR2DEC_4(str, i)  (CONV_STR2DEC_3(str, i)*10 + str[i+3]-'0')

// Custom "glue logic" to convert the month name to a usable number
#define GET_MONTH(str, i)      (str[i]=='J' && str[i+1]=='a' && str[i+2]=='n' ? 1 :     \
                                str[i]=='F' && str[i+1]=='e' && str[i+2]=='b' ? 2 :     \
                                str[i]=='M' && str[i+1]=='a' && str[i+2]=='r' ? 3 :     \
                                str[i]=='A' && str[i+1]=='p' && str[i+2]=='r' ? 4 :     \
                                str[i]=='M' && str[i+1]=='a' && str[i+2]=='y' ? 5 :     \
                                str[i]=='J' && str[i+1]=='u' && str[i+2]=='n' ? 6 :     \
                                str[i]=='J' && str[i+1]=='u' && str[i+2]=='l' ? 7 :     \
                                str[i]=='A' && str[i+1]=='u' && str[i+2]=='g' ? 8 :     \
                                str[i]=='S' && str[i+1]=='e' && str[i+2]=='p' ? 9 :     \
                                str[i]=='O' && str[i+1]=='c' && str[i+2]=='t' ? 10 :    \
                                str[i]=='N' && str[i+1]=='o' && str[i+2]=='v' ? 11 :    \
                                str[i]=='D' && str[i+1]=='e' && str[i+2]=='c' ? 12 : 0)

// extract the information from the time string given by __TIME__ and __DATE__
#define __TIME_SECONDS__        CONV_STR2DEC_2(__TIME__, 6)
#define __TIME_MINUTES__        CONV_STR2DEC_2(__TIME__, 3)
#define __TIME_HOURS__          CONV_STR2DEC_2(__TIME__, 0)
#define __TIME_DAYS__           CONV_STR2DEC_2(__DATE__, 4)
#define __TIME_MONTH__          GET_MONTH(__DATE__, 0)
#define __TIME_YEARS__          CONV_STR2DEC_4(__DATE__, 7)

// Days in February
#define _UNIX_TIMESTAMP_FDAY(year) \
    (((year) % 400) == 0UL ? 29UL : \
        (((year) % 100) == 0UL ? 28UL : \
            (((year) % 4) == 0UL ? 29UL : \
                28UL)))

// Days in the year
#define _UNIX_TIMESTAMP_YDAY(year, month, day) \
    ( \
        /* January */    day \
        /* February */ + (month >=  2 ? 31UL : 0UL) \
        /* March */    + (month >=  3 ? _UNIX_TIMESTAMP_FDAY(year) : 0UL) \
        /* April */    + (month >=  4 ? 31UL : 0UL) \
        /* May */      + (month >=  5 ? 30UL : 0UL) \
        /* June */     + (month >=  6 ? 31UL : 0UL) \
        /* July */     + (month >=  7 ? 30UL : 0UL) \
        /* August */   + (month >=  8 ? 31UL : 0UL) \
        /* September */+ (month >=  9 ? 31UL : 0UL) \
        /* October */  + (month >= 10 ? 30UL : 0UL) \
        /* November */ + (month >= 11 ? 31UL : 0UL) \
        /* December */ + (month >= 12 ? 30UL : 0UL) \
    )

// get the UNIX timestamp from a digits representation
#define _UNIX_TIMESTAMP(year, month, day, hour, minute, second) \
    ( /* time */ second \
                + minute * SEC_PER_MIN \
                + hour * SEC_PER_HOUR \
    + /* year day (month + day) */ (_UNIX_TIMESTAMP_YDAY(year, month, day) - 1) * SEC_PER_DAY \
    + /* year */ (year - 1970UL) * SEC_PER_YEAR \
                + ((year - 1969UL) / 4UL) * SEC_PER_DAY \
                - ((year - 1901UL) / 100UL) * SEC_PER_DAY \
                + ((year - 1601UL) / 400UL) * SEC_PER_DAY \
    )

// the UNIX timestamp
#define UNIX_TIMESTAMP (_UNIX_TIMESTAMP(__TIME_YEARS__, __TIME_MONTH__, __TIME_DAYS__, __TIME_HOURS__, __TIME_MINUTES__, __TIME_SECONDS__))

#endif
+8

timestamp.h . , ( ), , , - (Freescale CodeWarrior, AVR, MSVS...).

, AVR Windows ( , $(SolutionDir) AVR stuio, MSVS, , ):

FOR /F %%A IN ('C:\cygwin\bin\date +%s') DO SET BUILD_TIMESTAMP=%%A
echo #define BUILD_TIME %BUILD_TIMESTAMP% > "$(SolutionDir)timestamp.h"

C ( ...):

#include "../timestamp.h"

:

#define BUILD_TIME 1397317498

, "build project", , timestamp.h, include C.

, Cygwin (C:\cygwin\bin\date +%s), . Cygwin, Windows . ( 10 C:-) -.

+7

?

gcc -DCOMPILE_TIME=`date '+%s'` mysources.c
+3

: @Lưu Vĩnh Phúc, , : . . OP-.

time_t struct tm . , mktime() time_t.

time_t CompileTime = mktime(CompileTimeTM());
printf("%lld\n", (long long) CompileTime);

struct tm , .

else if ((d[3]=='M') && (d[4]=='a') && (d[5]=='y')) Print2Dig(5);

PIC, . __TIMESTAMP__.

// Dummy: used to detect a bad date parsing in Send_ID()
extern void BadDateM(void);

struct tm *CompileTimeTM(void) {
  static const char d[10] = __DATE__;
  static const char t[10] = __TIME__;
  static struct tm ct;

  ct.tm_year = (d[7]-'0')*10 + (d[8]-'0') + 2000 - 1900;

  #IGNORE_WARNINGS  204
  if (0) ;
  else if ((d[3]=='J') && (d[4]=='a') && (d[5]=='n')) ct.tm_mon = 1-1;
  else if ((d[3]=='F') && (d[4]=='e') && (d[5]=='b')) ct.tm_mon = 2-1;
  else if ((d[3]=='M') && (d[4]=='a') && (d[5]=='r')) ct.tm_mon = 3-1;
  else if ((d[3]=='A') && (d[4]=='p') && (d[5]=='r')) ct.tm_mon = 4-1;
  else if ((d[3]=='M') && (d[4]=='a') && (d[5]=='y')) ct.tm_mon = 5-1;
  else if ((d[3]=='J') && (d[4]=='u') && (d[5]=='n')) ct.tm_mon = 6-1;
  else if ((d[3]=='J') && (d[4]=='u') && (d[5]=='l')) ct.tm_mon = 7-1;
  else if ((d[3]=='A') && (d[4]=='u') && (d[5]=='g')) ct.tm_mon = 8-1;
  else if ((d[3]=='S') && (d[4]=='e') && (d[5]=='p')) ct.tm_mon = 9-1;
  else if ((d[3]=='O') && (d[4]=='c') && (d[5]=='t')) ct.tm_mon = 10-1;
  else if ((d[3]=='N') && (d[4]=='o') && (d[5]=='v')) ct.tm_mon = 11-1;
  else if ((d[3]=='D') && (d[4]=='e') && (d[5]=='c')) ct.tm_mon = 12-1;
  else BadDateM(); // compile this if no match above, and thus fail link.
  #IGNORE_WARNINGS  NONE

  ct.tm_mday = (d[0]-'0')*10 + (d[1]-'0');
  ct.tm_hour = (t[0]-'0')*10 + (t[1]-'0');
  ct.tm_min = (t[3]-'0')*10 + (t[4]-'0');
  ct.tm_sec = (t[6]-'0')*10 + (t[7]-'0');

  ct.tm_isdst = -1;  // information is not available.
  // ct.tm_yday = 0;
  // ct.tm_wday = 0;

  return &ct;
  }


struct tm *CompileTimeTM(void) { 
static const char d[10] = __DATE__; 
static const char t[10] = __TIME__; 
static struct tm ct; 

ct.tm_year = (d[7]-'0')*10 + (d[8]-'0') + 2000 - 1900; 
0F78 200724         MOV     #72,W4         : W4 = 72
0F7A 8864D4         MOV     W4,C9A         : C9A = W4

#IGNORE_WARNINGS  204 
if (0) ; 
else if ((d[3]=='J') && (d[4]=='a') && (d[5]=='n')) ct.tm_mon = 1-1; 
else if ((d[3]=='F') && (d[4]=='e') && (d[5]=='b')) ct.tm_mon = 2-1; 
else if ((d[3]=='M') && (d[4]=='a') && (d[5]=='r')) ct.tm_mon = 3-1; 
else if ((d[3]=='A') && (d[4]=='p') && (d[5]=='r')) ct.tm_mon = 4-1; 
0F7C 200034         MOV     #3,W4          : W4 = 3
0F7E 8864C4         MOV     W4,C98         : C98 = W4
else if ((d[3]=='M') && (d[4]=='a') && (d[5]=='y')) ct.tm_mon = 5-1; 
else if ((d[3]=='J') && (d[4]=='u') && (d[5]=='n')) ct.tm_mon = 6-1; 
else if ((d[3]=='J') && (d[4]=='u') && (d[5]=='l')) ct.tm_mon = 7-1; 
else if ((d[3]=='A') && (d[4]=='u') && (d[5]=='g')) ct.tm_mon = 8-1; 
else if ((d[3]=='S') && (d[4]=='e') && (d[5]=='p')) ct.tm_mon = 9-1; 
else if ((d[3]=='O') && (d[4]=='c') && (d[5]=='t')) ct.tm_mon = 10-1; 
else if ((d[3]=='N') && (d[4]=='o') && (d[5]=='v')) ct.tm_mon = 11-1; 
else if ((d[3]=='D') && (d[4]=='e') && (d[5]=='c')) ct.tm_mon = 12-1; 
else BadDateM(); // compile this if no match above, and thus fail link. 
#IGNORE_WARNINGS  NONE 

ct.tm_mday = (d[0]-'0')*10 + (d[1]-'0'); 
0F80 2000E4         MOV     #E,W4          : W4 = E
0F82 8864B4         MOV     W4,C96         : C96 = W4
ct.tm_hour = (t[0]-'0')*10 + (t[1]-'0'); 
0F84 2000B4         MOV     #B,W4          : W4 = B
0F86 8864A4         MOV     W4,C94         : C94 = W4
ct.tm_min = (t[3]-'0')*10 + (t[4]-'0'); 
0F88 200354         MOV     #35,W4         : W4 = 35
0F8A 886494         MOV     W4,C92         : C92 = W4
ct.tm_sec = (t[6]-'0')*10 + (t[7]-'0'); 
0F8C 2000D4         MOV     #D,W4          : W4 = D
0F8E 886484         MOV     W4,C90         : C90 = W4
+1

:

#include <stdio.h>
#define dec(ch) ((ch)-'0')
#define t(index, multiplier)    (dec(__TIME__[index]) * (multiplier))
/* only minutes and seconds - you get the idea */
#define mmss()  (t(3,600) + t(4,60) + t(6,10) + t(7,1))
int main()
{
        /*
        int i;
        printf("time = %s\n", __TIME__);
        for(i=0; __TIME__[i]; i++)
                printf("t(%d) = %d\n", i, t(i,1));
        */
        printf("mmss = %d\n", mmss());
        return 0;
}

gcc -O ; time_t __DATE__ .

- , ;)

: , , , C, (, , ...)

+1
/**
 * @brief  Macros to get integer build timestamp:
 *         __DATE_TIME_Y2K__  seconds since 2000-01-01,00:00:00
 *         __DATE_TIME_UNIX__ seconds since 1970-01-01 00:00:00
 *
 *           01234567890              01234567
 * __DATE__ "Jul 27 2019"   __TIME__ "12:34:56"
 */
#ifndef __DATE_TIME_H__
#define __DATE_TIME_H__

#define Y2K_UNIX_EPOCH_DIFF 946684800U
#define YEARS ((__DATE__[10] - '0' + (__DATE__[9] - '0') * 10))
#define DAY_OF_MONTH ((__DATE__[5] - '0') \
                  + (((__DATE__[4] > '0')? __DATE__[4] - '0': 0) * 10) - 1)
#define DAY_OF_YEAR ((DAY_OF_MONTH) + \
( /* Jan */ (__DATE__[0] == 'J' && __DATE__[1] == 'a')?   0: \
  /* Feb */ (__DATE__[0] == 'F'                      )?  31: \
  /* Mar */ (__DATE__[0] == 'M' && __DATE__[2] == 'r')?  59: \
  /* Apr */ (__DATE__[0] == 'A' && __DATE__[1] == 'p')?  90: \
  /* May */ (__DATE__[0] == 'M'                      )? 120: \
  /* Jun */ (__DATE__[0] == 'J' && __DATE__[2] == 'n')? 151: \
  /* Jul */ (__DATE__[0] == 'J'                      )? 181: \
  /* Aug */ (__DATE__[0] == 'A'                      )? 212: \
  /* Sep */ (__DATE__[0] == 'S'                      )? 243: \
  /* Oct */ (__DATE__[0] == 'O'                      )? 273: \
  /* Nov */ (__DATE__[0] == 'N'                      )? 304: \
  /* Dec */                                             334  ))
#define LEAP_DAYS (YEARS / 4 + 1 + ((YEARS % 4 == 0 && DAY_OF_YEAR > 58)? 1 : 0) )
#define __DATE_TIME_Y2K__ ( (YEARS * 365 + LEAP_DAYS + DAY_OF_YEAR ) * 86400 \
                    + ((__TIME__[0] - '0') * 10 + __TIME__[1] - '0') * 3600 \
                    + ((__TIME__[3] - '0') * 10 + __TIME__[4] - '0') * 60 \
                    + ((__TIME__[6] - '0') * 10 + __TIME__[7] - '0') )
#define  __DATE_TIME_UNIX__ ( __DATE_TIME_Y2K__ + Y2K_UNIX_EPOCH_DIFF )
#endif /* __DATE_TIME_H__ */

, @nqtronix, . !

. 2000-01-01,00: 00: 00 2099-12-31,23: 59: 59.

+1

, , 10 -

       // special case to handle __DATE__ not inserting leading zero on day of month
       // if Day of month is less than 10 - it inserts a blank character
       // this results in a negative number for tm_mday 

       if(d[4] == ' ')
       {
    	   ct.tm_mday =  d[5]-'0';
       }
       else
       {
    	   ct.tm_mday = (d[4]-'0')*10 + (d[5]-'0');
       }
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