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1 | .\" Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl> |
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13 | .\" manual page may be incorrect or out-of-date.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 | .TH TIMEGM 3 2001-12-26 "GNU" "Linux Programmer's Manual" | |
24 | .SH NAME | |
25 | timegm, timelocal \- inverses for gmtime and localtime | |
26 | .SH SYNOPSIS | |
27 | .nf | |
28 | .B #include <time.h> | |
29 | .sp | |
b9f02710 | 30 | .BI "time_t timelocal(struct tm *" tm ); |
fea681da | 31 | .sp |
b9f02710 | 32 | .BI "time_t timegm(struct tm *" tm ); |
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33 | .SH DESCRIPTION |
34 | The functions | |
63aa9df0 | 35 | .BR timelocal () |
fea681da | 36 | and |
63aa9df0 | 37 | .BR timegm () |
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38 | are the inverses to |
39 | .BR localtime (3) | |
40 | and | |
41 | .BR gmtime (3). | |
42 | .SH NOTES | |
43 | These functions are GNU extensions. | |
44 | The | |
63aa9df0 | 45 | .BR timelocal () |
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46 | function is equivalent to the POSIX standard function |
47 | .BR mktime (3). | |
48 | There is no reason to ever use it. | |
49 | .LP | |
50 | For a portable version of | |
63aa9df0 | 51 | .BR timegm (), |
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52 | set the |
53 | .B TZ | |
54 | environment variable to UTC, call | |
63aa9df0 | 55 | .BR mktime () |
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56 | and restore the value of |
57 | .BR TZ . | |
58 | Something like | |
59 | ||
60 | .RS | |
61 | .nf | |
62 | #include <time.h> | |
63 | #include <stdlib.h> | |
64 | ||
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65 | time_t |
66 | my_timegm(struct tm *tm) | |
67 | { | |
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68 | time_t ret; |
69 | char *tz; | |
70 | ||
71 | tz = getenv("TZ"); | |
72 | setenv("TZ", "", 1); | |
73 | tzset(); | |
74 | ret = mktime(tm); | |
75 | if (tz) | |
76 | setenv("TZ", tz, 1); | |
77 | else | |
78 | unsetenv("TZ"); | |
79 | tzset(); | |
80 | return ret; | |
81 | } | |
82 | .fi | |
83 | .RE | |
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84 | .SH "CONFORMING TO" |
85 | Not in POSIX.1-2001. | |
86 | Present on the BSDs. | |
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87 | .SH "SEE ALSO" |
88 | .BR gmtime (3), | |
89 | .BR localtime (3), | |
90 | .BR mktime (3), | |
91 | .BR tzset (3) |