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1.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
2.\"
3.\" Permission is granted to make and distribute verbatim copies of this
4.\" manual provided the copyright notice and this permission notice are
5.\" preserved on all copies.
6.\"
7.\" Permission is granted to copy and distribute modified versions of this
8.\" manual under the conditions for verbatim copying, provided that the
9.\" entire resulting derived work is distributed under the terms of a
10.\" permission notice identical to this one.
11.\"
12.\" Since the Linux kernel and libraries are constantly changing, this
13.\" manual page may be incorrect or out-of-date. The author(s) assume no
14.\" responsibility for errors or omissions, or for damages resulting from
15.\" the use of the information contained herein. The author(s) may not
16.\" have taken the same level of care in the production of this manual,
17.\" which is licensed free of charge, as they might when working
18.\" professionally.
19.\"
20.\" Formatted or processed versions of this manual, if unaccompanied by
21.\" the source, must acknowledge the copyright and authors of this work.
22.\"
23.\" References consulted:
24.\" Linux libc source code
25.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
26.\" 386BSD man pages
27.\" Modified Sat Jul 24 19:48:17 1993 by Rik Faith (faith@cs.unc.edu)
28.TH DIFFTIME 3 1993-07-02 "GNU" "Linux Programmer's Manual"
29.SH NAME
30difftime \- calculate time difference
31.SH SYNOPSIS
32.nf
33.B #include <time.h>
34.sp
35.BI "double difftime(time_t " time1 ", time_t " time0 );
36.fi
37.SH DESCRIPTION
38The \fBdifftime()\fP function returns the number of seconds elapsed
39between time \fItime1\fP and time \fItime0\fP, represented as a double.
40The two times are specified in calendar time, which represents the time
41elapsed since the Epoch
42(00:00:00 on January 1, 1970, Coordinated Universal Time (UTC)).
43.SH "CONFORMING TO"
44SVID 3, BSD 4.3, ISO 9899
45.SH NOTES
46This function is required by ANSI C.
47On a POSIX system, time_t is an arithmetic type, and one could just
48define
49.RS
50.nf
2bc2f479 51#define difftime(t1,t0) (double)(t1 \- t0)
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52.fi
53.RE
54when the possible overflow in the subtraction is not a concern.
55.SH "SEE ALSO"
56.BR date (1),
57.BR gettimeofday (2),
58.BR time (2),
59.BR ctime (3),
60.BR gmtime (3),
61.BR localtime (3)