time.h

how to measure pipe syscall time in milliseconds?

本小妞迷上赌 提交于 2019-12-02 11:29:15
问题 I want to see the time of my pipe program system call. I need to measure it for analyzing results. How can i measure the time of system call in milliseconds? For example, this is simple pipe program: #include <unistd.h> #include <stdlib.h> #include <stdio.h> #include <string.h> #include <sys/timeb.h> #include <time.h> void main() { FILE *read_fp; char buffer[10]; int cnt; memset(buffer,'\0',sizeof(buffer)); read_fp=popen("uname -a","|"); if (read_fp!=NULL) { cnt=fread(buffer,sizeof(char),9

How can adding a header increase portability? (sys/time.h)

时光总嘲笑我的痴心妄想 提交于 2019-12-02 03:36:42
I just noticed this line in the getrusage man page: Including <sys/time.h> is not required these days, but increases portability. (Indeed, struct timeval is defined in <sys/time.h> ) What? Since struct rusage contains struct timeval as a member, surely sys/resource.h must include sys/time.h or the type would be incomplete and unusable? How could this comment ever have made sense? How could it ever have not been necessary? How could portability have ever been helped? In general, it was not uncommon in the early days of C for you to have to manually include header file A before header file B.

How do I get milliseconds since midnight UTC in C?

你。 提交于 2019-11-30 20:23:24
The time function in time.h gives milliseconds since the epoch. This is the precise way: struct timeval tv; int msec = -1; if (gettimeofday(&tv, NULL) == 0) { msec = ((tv.tv_sec % 86400) * 1000 + tv.tv_usec / 1000); } That will store into msec the number of milliseconds since midnight. (Or -1 if there was an error getting the time.) Although it's usually a bad idea to store time-values in an int , I'm being a little cavalier and assuming int is at least 32-bit, and can easily accommodate the range (-1) to 86,400,000. But I don't know if it's worth all the effort. This is a simple way: time_t

C++ system file bits/stat.h suddenly breaks with “error: field ‘st_atim’ has incomplete type”

十年热恋 提交于 2019-11-30 15:57:09
问题 I'm porting over a large, old system that was known to work, onto Ubuntu 64-bit Linux. The system uses FLTK, upgrading to 1.3.2, and I'm using NetBeans. A file includes basic universal /FL/Fl.H as its first line. This includes the newer unicode enabler /FL/fl_utf8.h. This includes system file <sys/stat.h> , which then includes system file <bits/stat.h> . When wiring this up, and -I including various different directories, all of a sudden the system files break at compile time with: In file

C++ system file bits/stat.h suddenly breaks with “error: field ‘st_atim’ has incomplete type”

偶尔善良 提交于 2019-11-30 15:23:45
I'm porting over a large, old system that was known to work, onto Ubuntu 64-bit Linux. The system uses FLTK, upgrading to 1.3.2, and I'm using NetBeans. A file includes basic universal /FL/Fl.H as its first line. This includes the newer unicode enabler /FL/fl_utf8.h. This includes system file <sys/stat.h> , which then includes system file <bits/stat.h> . When wiring this up, and -I including various different directories, all of a sudden the system files break at compile time with: In file included from /usr/include/sys/stat.h:107, /usr/include/bits/stat.h:88: error: field ‘st_atim’ has

How can i get UTCTime in millisecond since January 1, 1970 in c language

余生长醉 提交于 2019-11-27 15:44:20
问题 Is there any way to get milliseconds and its fraction part from 1970 using time.h in c language? 回答1: This works on Ubuntu Linux: #include <sys/time.h> ... struct timeval tv; gettimeofday(&tv, NULL); unsigned long long millisecondsSinceEpoch = (unsigned long long)(tv.tv_sec) * 1000 + (unsigned long long)(tv.tv_usec) / 1000; printf("%llu\n", millisecondsSinceEpoch); At the time of this writing, the printf() above is giving me 1338850197035. You can do a sanity check at the TimestampConvert.com

C++ error: undefined reference to 'clock_gettime' and 'clock_settime'

╄→гoц情女王★ 提交于 2019-11-27 10:42:12
I am pretty new to Ubuntu, but I can't seem to get this to work. It works fine on my school computers and I don't know what I am not doing. I have checked usr/include and time.h is there just fine. Here is the code: #include <iostream> #include <time.h> using namespace std; int main() { timespec time1, time2; int temp; clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time1); //do stuff here clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time2); return 0; } I am using CodeBlocks as my IDE to build and run as well. Any help would be great, thank you. Dmitry Yudakov Add -lrt to the end of g++ command line.