How to use nanosleep in C What are tim tv sec and tim tv nsec

Question

What is the use of tim tv sec and tim tv nsec in the following   How can I sleep execution for 500000 microseconds    include  lt stdio h gt   include  lt time h gt   int main        struct timespec tim  tim2     tim tv sec   1     tim tv nsec   500      if nanosleep  amp tim    amp tim2   lt  0                 printf  Nano sleep system call failed  n          return -1           printf  Nano sleep successfull  n        return 0

User · Answer

500000 microseconds are 500000000 nanoseconds  You only wait for 500 ns   0 5   s

User · Answer

POSIX 7  First find the function  http   pubs opengroup org onlinepubs 9699919799 functions nanosleep html  That contains a link to a time h  which as a header should be where structs are defined      The  header shall declare the timespec structure  which shall   include at least the following members   time t  tv sec    Seconds   long    tv nsec   Nanoseconds     man 2 nanosleep  Pseudo-official glibc docs which you should always check for syscalls   struct timespec       time t tv sec            seconds        long   tv nsec           nanoseconds

User · Answer

Half a second is 500 000 000 nanoseconds  so your code should read   tim tv sec    0  tim tv nsec   500000000L    As things stand  you code is sleeping for 1 0000005s  1s   500ns

User · Answer

This worked for me        include  lt stdio h gt   include  lt time h gt       Needed for struct timespec      int nsleep long miliseconds       struct timespec req  rem      if miliseconds  gt  999                  req tv sec    int  miliseconds   1000                                 Must be Non-Negative            req tv nsec    miliseconds -   long req tv sec   1000     1000000     Must be in range of 0 to 999999999               else                 req tv sec   0                             Must be Non-Negative            req tv nsec   miliseconds   1000000        Must be in range of 0 to 999999999                return nanosleep  amp req    amp rem      int main        int ret   nsleep 2500      printf  sleep result  d n  ret      return 0

User · Answer

More correct variant     struct timespec delta    5   secs    135   nanosecs     while  nanosleep  amp delta   amp delta

User · Answer

tv nsec is the sleep time in nanoseconds  500000us   500000000ns  so you want   nanosleep  const struct timespec     0  500000000L    NULL

User · Answer

I usually use some  define and constants to make the calculation easy    define NANO SECOND MULTIPLIER  1000000     1 millisecond   1 000 000 Nanoseconds const long INTERVAL MS   500   NANO SECOND MULTIPLIER    Hence my code would look like this   timespec sleepValue    0    sleepValue tv nsec   INTERVAL MS  nanosleep  amp sleepValue  NULL

[c] How to use nanosleep() in C? What are `tim.tv_sec` and `tim.tv_nsec`?

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