How do I get the unix timestamp in C as an int

Question

I would like to get the current timestamp and print it out using fprintf

User · Answer

include  lt stdio h gt   include  lt time h gt   int main         time t seconds      seconds   time NULL      printf  Seconds since January 1  1970    ld n   seconds       return 0       And will get similar result   Seconds since January 1  1970   1476107865

User · Answer

For 32-bit systems   fprintf stdout    u n    unsigned time NULL       For 64-bit systems   fprintf stdout    lu n    unsigned long time NULL

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An important point is to consider if you perform tasks based on difference between 2 timestamps because you will get odd behavior if you generate it with gettimeofday    and even clock gettime CLOCK REALTIME     at the moment where you will set the time of your system  To prevent such problem  use clock gettime CLOCK MONOTONIC RAW   amp tms  instead

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Is just casting the value returned by time     include  lt stdio h gt   include  lt time h gt   int main void        printf  Timestamp   d n   int time NULL        return 0      what you want     gcc -Wall -Wextra -pedantic -std c99 tstamp c  amp  amp    a out Timestamp  1343846167   To get microseconds since the epoch  from C11 on  the portable way is to use  int timespec get struct timespec  ts  int base    Unfortunately  C11 is not yet available everywhere  so as of now  the closest to portable is using one of the POSIX functions clock gettime or gettimeofday  marked obsolete in POSIX 1-2008  which recommends clock gettime    The code for both functions is nearly identical    include  lt stdio h gt   include  lt time h gt   include  lt stdint h gt   include  lt inttypes h gt   int main void         struct timespec tms          The C11 way           if    timespec get  amp tms  TIME UTC                POSIX 1-2008 way        if  clock gettime CLOCK REALTIME  amp tms             return -1               seconds  multiplied with 1 million        int64 t micros   tms tv sec   1000000         Add full microseconds        micros    tms tv nsec 1000         round up if necessary        if  tms tv nsec   1000  gt   500              micros            printf  Microseconds    PRId64  n  micros       return 0

User · Answer

With second precision  you can print tv sec field of timeval structure that you get from gettimeofday   function  For example    include  lt sys time h gt   include  lt stdio h gt   int main         struct timeval tv      gettimeofday  amp tv  NULL       printf  Seconds since Jan  1  1970   ld n   tv tv sec       return 0      Example of compiling and running     gcc -Wall -o test   test c      test  Seconds since Jan  1  1970  1343845834   Note  however  that its been a while since epoch and so long int is used to fit a number of seconds these days   There are also functions to print human-readable times  See this manual page for details  Here goes an example using ctime      include  lt time h gt   include  lt stdio h gt   int main         time t clk   time NULL       printf   s   ctime  amp clk        return 0      Example run  amp  output     gcc -Wall -o test   test c      test  Wed Aug  1 14 43 23 2012

[c] How do I get the unix timestamp in C as an int?

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