Formatting struct timespec

Question

How to format struct timespec to string  This structure is returned e g  by clock gettime   on Linux gcc   struct timespec       time t   tv sec            seconds        long     tv nsec           nanoseconds

User · Accepted Answer

One way to format it is  printf  quot  lld   9ld quot    long long ts tv sec  ts tv nsec

User · Answer

You can pass the tv sec parameter to some of the formatting function  Have a look at gmtime  localtime    Then look at snprintf

User · Answer

I wanted to ask the same question  Here is my current solution to obtain a string like this  2013-02-07 09 24 40 749355372 I am not sure if there is a more straight forward solution than this  but at least the string format is freely configurable with this approach    include  lt stdio h gt   include  lt stdlib h gt   include  lt string h gt   include  lt time h gt    define NANO 1000000000L     buf needs to store 30 characters int timespec2str char  buf  uint len  struct timespec  ts        int ret      struct tm t       tzset        if  localtime r  amp  ts- gt tv sec    amp t     NULL          return 1       ret   strftime buf  len    F  T    amp t       if  ret    0          return 2      len -  ret - 1       ret   snprintf  amp buf strlen buf    len     09ld   ts- gt tv nsec       if  ret  gt   len          return 3       return 0     int main int argc  char   argv        clockid t clk id   CLOCK REALTIME      const uint TIME FMT   strlen  2012-12-31 12 59 59 123456789     1      char timestr TIME FMT        struct timespec ts  res      clock getres clk id   amp res       clock gettime clk id   amp ts        if  timespec2str timestr  sizeof timestr    amp ts     0            printf  timespec2str failed  n            return EXIT FAILURE        else           unsigned long resol   res tv sec   NANO   res tv nsec          printf  CLOCK REALTIME  res  ld ns  time  s n   resol  timestr           return EXIT SUCCESS            output   gcc mwe c -lrt      a out  CLOCK REALTIME  res 1 ns  time 2013-02-07 13 41 17 994326501

User · Answer

The following will return an ISO8601 and RFC3339-compliant UTC timestamp  including nanoseconds  It uses strftime    which works with struct timespec just as well as with struct timeval because all it cares about is the number of seconds  which both provide  Nanoseconds are then appended  careful to pad with zeros   as well as the UTC suffix  Z   Example output  2021-01-19T04 50 01 435561072Z  include  lt stdio h gt   include  lt time h gt   include  lt sys time h gt   int utc system timestamp char      int main void        char buf 31       utc system timestamp buf       printf  quot  s n quot   buf         Allocate exactly 31 bytes for buf int utc system timestamp char buf              const int bufsize   31          struct timespec now          struct tm tm          int retval   clock gettime CLOCK REALTIME   amp now           gmtime r  amp now tv sec   amp tm           strftime buf  bufsize   quot  Y- m- dT H  M  S  quot    amp tm           sprintf buf   quot  s 09luZ quot   buf  now tv nsec           return retval

User · Answer

You could use a std  stringstream  You can stream anything into it   std  stringstream stream  stream  lt  lt  5 7  stream  lt  lt  foo bar   std  string s   stream str      That should be a quite general approach   Works only for C    but you asked the question for this language too

[c] Formatting struct timespec

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