Calendar time counts the number of seconds since the Epoch, 00:00:00 January 1, 1970 Coordinated Universal Time (UTC). This is used by the operating system for tasks such as determining which a file was last used.
Processor time is cpu time. It is used by the operating system to measure resource usage. Processor time is measured in clock ticks.
Using time at the command line yields a combination of these. 90.7u 12.9s 2:39 65% means
| call | protocol | example | time value | |||||||||||||||||||
| time() | #include <time.h> time_t time(time_t *calptr); |
real time (wall clock) also stores time value in place pointed to by calptr | ||||||||||||||||||||
| gmtime() | #include <time.h> struct tm *gmtime(const time_t *calptr); |
from real time to broken down time | ||||||||||||||||||||
| mktime() | #include <time.h> time_t mktime( struct tm *tmptr); |
from broken down time to real time | ||||||||||||||||||||
| localtime() | #include <time.h> struct tm *localtime(const time_t *calptr); |
from real time to broken down time | ||||||||||||||||||||
| ctime() | #include <time.h> char *ctime(const time_t *clock); |
from real time to ascii real time (wall clock) returned in 26-character buffer
| ||||||||||||||||||||
| asctime() | #include <time.h> char *asctime(const struct tm *tmptr); |
from broken down time to ascii real time | ||||||||||||||||||||
| strftime() | #include <time.h> size_t strftime(char *buf, size_t maxsize, const char *format, const struct tm *tmptr); |
from broken down time to formatted string | ||||||||||||||||||||
| times() | #include <sys/times.h> clock_t times (struct tms *buffer); | example 6.1 | from broken down time to virtual time (time in run state) returns info about process and its children in struct tms | |||||||||||||||||||
| gettimeofday() | #include <sys/times.h> int gettimeofday (struct timeval *tp, void *tzp); | example 6.2 | real time with greater accuracy | |||||||||||||||||||
| clock_setitimer() | #include <sys/times.h> int clock_setitimer(int which, const struct itimerval *value, struct itimeval *ovalue); | program 6.1 | interval timer for user - set it | |||||||||||||||||||
| clock_getitimer() | #include <sys/times.h> int clock_getitimer(int which, struct itimerval *value); | program 6.2 | interval timer for user - get the time remaining |
| name |
manpage section | purpose |
| adjtimex | (2) | - tune kernel clock |
| asctime [ctime] | (3) | - transform binary date and time to ASCII |
| clock | (3) | - Determine processor time |
| clockdiff | (8) | - Measures clock difference between us and
destination with 1msec resolution. Without -o option it uses icmp timestamps, with -o it uses icmp echo with timestamp IP option |
| ctime | (3) | - transform binary date and time to ASCII |
| date | (1) | - print or set the system date and time |
| difftime | (3) | - calculate time difference |
| ftime | (3) | - return date and time |
| getitimer | (2) | - get or set value of an interval timer |
| gettimeofday | (2) | - get / set time |
| gmtime [ctime] | (3) | - transform binary date and time to ASCII |
| gtt | (1) | - GTimeTracker - a time tracker |
| localtime [ctime] | (3) | - transform binary date and time to ASCII |
| mktime [ctime] | (3) | - transform binary date and time to ASCII |
| nanosleep | (2) | - pause execution for a specified time |
| newer | (1) | - compare file modification times |
| profil | (3) | - execution time profile |
| rdate | (1) | - get the time via the network |
| ruptime | (1) | - show host status of local machines |
| setitimer [getitimer] | (2) | - get or set value of an interval timer |
| settimeofday [gettimeofday] | (2) | - get / set time |
| sleep | (1) | - delay for a specified amount of time |
| stime | (2) | - set time |
| strftime | (3) | - format date and time |
| strptime | (3) | - convert a string representation of time to a time tm structure |
| sysconf | (3) | - Get configuration information at runtime |
| sysctl | (8) | - configure kernel parameters at runtime |
| time | (2) | - get time in seconds |
| timeconfig | (8) | - simple interface for configuring system time parameters |
| timed | (8) | - time server daemon |
| timedc | (8) | - timed control program |
| times | (2) | - get process times |
| times [builtins2] | (1) | - bash built-in commands, see bash(1) |
| tzfile | (5) | - time zone information |
| tzselect | (8) | - select a time zone |
| tzset | (3) | - initialize time conversion information |
| uptime | (1) | - Tell how long the system has been running |
| t3d | (1) | - clock using flying balls to display the time |
| Benchmark | (3) | - benchmark running times of code |
| Time::Local | (3) | - efficiently compute time from local and GMT time |
| Time::gmtime | (3) | - by-name interface to Perl's built-in gmtime() function |
| Time::localtime | (3) | - by-name interface to Perl's built-in localtime() function |
| Time::tm | (3) | - internal object used by Time::gmtime and Time::localtime |
| timeit [Benchmark] | (3) | - run a chunk of code and see how long it goes |
| timethese [Benchmark] | (3) | - run several chunks of code several times |
| timethis [Benchmark] | (3) | - run a chunk of code several times |
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