How to get the current time in milliseconds from C in Linux

Question

How do I get the current time on Linux in milliseconds

User · Answer

Following is the util function to get current timestamp in milliseconds:

#include <sys/time.h>

long long current_timestamp() {
    struct timeval te; 
    gettimeofday(&te, NULL); // get current time
    long long milliseconds = te.tv_sec*1000LL + te.tv_usec/1000; // calculate milliseconds
    // printf("milliseconds: %lld\n", milliseconds);
    return milliseconds;
}

About timezone:

gettimeofday() support to specify timezone, I use NULL, which ignore the timezone, but you can specify a timezone, if need.

@Update - timezone

Since the long representation of time is not relevant to or effected by timezone itself, so setting tz param of gettimeofday() is not necessary, since it won't make any difference.

And, according to man page of gettimeofday(), the use of the timezone structure is obsolete, thus the tz argument should normally be specified as NULL, for details please check the man page.

User · Answer

This can be achieved using the POSIX clock gettime function   In the current version of POSIX  gettimeofday is marked obsolete  This means it may be removed from a future version of the specification  Application writers are encouraged to use the clock gettime function instead of gettimeofday   Here is an example of how to use clock gettime    define  POSIX C SOURCE 200809L   include  lt inttypes h gt   include  lt math h gt   include  lt stdio h gt   include  lt time h gt   void print current time with ms  void        long            ms     Milliseconds     time t          s      Seconds     struct timespec spec       clock gettime CLOCK REALTIME   amp spec        s    spec tv sec      ms   round spec tv nsec   1 0e6      Convert nanoseconds to milliseconds     if  ms  gt  999            s            ms   0             printf  Current time    PRIdMAX   03ld seconds since the Epoch n               intmax t s  ms       If your goal is to measure elapsed time  and your system supports the  monotonic clock  option  then you should consider using CLOCK MONOTONIC instead of CLOCK REALTIME

User · Answer

Derived from Dan Moulding s POSIX answer  this should work    include  lt time h gt   include  lt math h gt   long millis        struct timespec  t      clock gettime CLOCK REALTIME   amp  t       return  t tv sec 1000   lround  t tv nsec 1 0e6      Also as pointed out by David Guyon  compile with -lm

User · Answer

This version need not math library and checked the return value of clock gettime     include  lt time h gt   include  lt stdlib h gt   include  lt stdint h gt           return milliseconds     uint64 t get now time       struct timespec spec    if  clock gettime 1   amp spec     -1       1 is CLOCK MONOTONIC        abort           return spec tv sec   1000   spec tv nsec   1e6

User · Answer

C11 timespec get  It returns up to nanoseconds  rounded to the resolution of the implementation   It is already implemented in Ubuntu 15 10  API looks the same as the POSIX clock gettime    include  lt time h gt  struct timespec ts  timespec get  amp ts  TIME UTC   struct timespec       time t   tv sec            seconds        long     tv nsec           nanoseconds         More details here  https   stackoverflow com a 36095407 895245

User · Answer

Use gettimeofday   to get the time in seconds and microseconds  Combining and rounding to milliseconds is left as an exercise

User · Answer

You have to do something like this   struct timeval  tv  gettimeofday  amp tv  NULL    double time in mill              tv tv sec    1000    tv tv usec    1000      convert tv sec  amp  tv usec to millisecond

[c] How to get the current time in milliseconds from C in Linux?

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