projects / unix-history / blame
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1 | .\" Copyright (c) 1980 Regents of the University of California. |
| 2 | .\" All rights reserved. The Berkeley software License Agreement | |
| 3 | .\" specifies the terms and conditions for redistribution. | |
| 4 | .\" | |
| 5 | .\" @(#)ctime.3 4.1 (Berkeley) %G% | |
| 6 | .\" | |
| 7 | .TH CTIME 3 | |
| 8 | .UC 4 | |
| 9 | .SH NAME | |
| 10 | ctime, localtime, gmtime, asctime, timezone \- convert date and time to ASCII | |
| 11 | .SH SYNOPSIS | |
| 12 | .nf | |
| 13 | .B char *ctime(clock) | |
| 14 | .B long *clock; | |
| 15 | .PP | |
| 16 | .B #include <time.h> | |
| 17 | .PP | |
| 18 | .B struct tm *localtime(clock) | |
| 19 | .B long *clock; | |
| 20 | .PP | |
| 21 | .B struct tm *gmtime(clock) | |
| 22 | .B long *clock; | |
| 23 | .PP | |
| 24 | .B char *asctime(tm) | |
| 25 | .B struct tm *tm; | |
| 26 | .PP | |
| 27 | .B char *timezone(zone, dst) | |
| 28 | .fi | |
| 29 | .SH DESCRIPTION | |
| 30 | .I Ctime | |
| 31 | converts a time pointed to by | |
| 32 | .I clock | |
| 33 | such as returned by | |
| 34 | .IR time (2) | |
| 35 | into ASCII | |
| 36 | and returns a pointer to a | |
| 37 | 26-character string | |
| 38 | in the following form. | |
| 39 | All the fields have constant width. | |
| 40 | .PP | |
| 41 | Sun Sep 16 01:03:52 1973\\n\\0 | |
| 42 | .PP | |
| 43 | .I Localtime | |
| 44 | and | |
| 45 | .I gmtime | |
| 46 | return pointers to structures containing | |
| 47 | the broken-down time. | |
| 48 | .I Localtime | |
| 49 | corrects for the time zone and possible daylight savings time; | |
| 50 | .I gmtime | |
| 51 | converts directly to GMT, which is the time UNIX uses. | |
| 52 | .I Asctime | |
| 53 | converts a broken-down time to ASCII and returns a pointer | |
| 54 | to a 26-character string. | |
| 55 | .PP | |
| 56 | The structure declaration from the include file is: | |
| 57 | .RS | |
| 58 | .PP | |
| 59 | .nf | |
| 60 | .so /usr/include/time.h | |
| 61 | .fi | |
| 62 | .RE | |
| 63 | .PP | |
| 64 | These quantities give the time on a 24-hour clock, | |
| 65 | day of month (1-31), month of year (0-11), day of week | |
| 66 | (Sunday = 0), year \- 1900, day of year (0-365), | |
| 67 | and a flag that is nonzero if daylight saving time is in effect. | |
| 68 | .PP | |
| 69 | When local time is called for, | |
| 70 | the program consults the system to determine the time zone and | |
| 71 | whether the standard U.S.A. daylight saving time adjustment is | |
| 72 | appropriate. | |
| 73 | The program knows about the peculiarities | |
| 74 | of this conversion in 1974 and 1975; | |
| 75 | if necessary, | |
| 76 | a table for these years can be extended. | |
| 77 | .PP | |
| 78 | .I Timezone | |
| 79 | returns the name of the time zone associated with its first argument, | |
| 80 | which is measured in minutes westward from Greenwich. | |
| 81 | If the second argument is 0, the standard name is used, | |
| 82 | otherwise the Daylight Saving version. | |
| 83 | If the required name does not appear in a table | |
| 84 | built into the routine, | |
| 85 | the difference from GMT is produced; e.g. | |
| 86 | in Afghanistan | |
| 87 | .I timezone(-(60*4+30), 0) | |
| 88 | is appropriate because it is 4:30 ahead of GMT | |
| 89 | and the string | |
| 90 | .B GMT+4:30 | |
| 91 | is produced. | |
| 92 | .SH "SEE ALSO" | |
| 93 | time(2) | |
| 94 | .SH BUGS | |
| 95 | The return values point to static data | |
| 96 | whose content is overwritten by each call. |