System Grab Bag

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Name

difftime - calculate time difference

Library

Standard C library ( libc ", " -lc )

Synopsis

#include <time.h> 
double difftime(time_t " time1 ", time_t  time0 );

Description

The difftime() function returns the number of seconds elapsed between time time1 and time time0, represented as a double. Each of the times is specified in calendar time, which means its value is a measurement (in seconds) relative to the Epoch, 1970-01-01 00:00:00 +0000 (UTC).

Attributes

For an explanation of the terms used in this section, see attributes(7). allbox; lbx lb lb T{ difftime()
InterfaceAttributeValue
T}Thread safetyMT-Safe

Standards

C11, POSIX.1-2008.

History

POSIX.1-2001, C89, SVr4, 4.3BSD.

Notes

On a POSIX system, time_t is an arithmetic type, and one could just define 

#define my_difftime(t1,t0) (double)(t1 - t0)

when the possible overflow in the subtraction is not a concern.

See Also

  1. date(1),
  2. gettimeofday(2),
  3. time(2),
  4. ctime(3),
  5. gmtime(3),
  6. localtime(3)