diff --git a/lib/libc/stdtime/ctime.3 b/lib/libc/stdtime/ctime.3 index b347e5362948..2aaf94f2b12a 100644 --- a/lib/libc/stdtime/ctime.3 +++ b/lib/libc/stdtime/ctime.3 @@ -1,404 +1,391 @@ .\" Copyright (c) 1989, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" This code is derived from software contributed to Berkeley by .\" Arthur Olson. .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" From: @(#)ctime.3 8.1 (Berkeley) 6/4/93 .\" $FreeBSD$ .\" -.Dd March 6, 2023 +.Dd April 20, 2023 .Dt CTIME 3 .Os .Sh NAME .Nm asctime , .Nm asctime_r , .Nm ctime , .Nm ctime_r , .Nm difftime , .Nm gmtime , .Nm gmtime_r , .Nm localtime , .Nm localtime_r , .Nm mktime , .Nm timegm .Nd transform binary date and time values .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In time.h .Vt extern char *tzname[2] ; .Ft char * +.Fn asctime "const struct tm *tm" +.Ft char * +.Fn asctime_r "const struct tm *tm" "char *buf" +.Ft char * .Fn ctime "const time_t *clock" +.Ft char * +.Fn ctime_r "const time_t *clock" "char *buf" .Ft double .Fn difftime "time_t time1" "time_t time0" -.Ft char * -.Fn asctime "const struct tm *tm" +.Ft struct tm * +.Fn gmtime "const time_t *clock" +.Ft struct tm * +.Fn gmtime_r "const time_t *clock" "struct tm *result" .Ft struct tm * .Fn localtime "const time_t *clock" .Ft struct tm * -.Fn gmtime "const time_t *clock" +.Fn localtime_r "const time_t *clock" "struct tm *result" .Ft time_t .Fn mktime "struct tm *tm" .Ft time_t .Fn timegm "struct tm *tm" -.Ft char * -.Fn ctime_r "const time_t *clock" "char *buf" -.Ft struct tm * -.Fn localtime_r "const time_t *clock" "struct tm *result" -.Ft struct tm * -.Fn gmtime_r "const time_t *clock" "struct tm *result" -.Ft char * -.Fn asctime_r "const struct tm *tm" "char *buf" .Sh DESCRIPTION -The functions +The .Fn ctime , -.Fn gmtime +.Fn gmtime , and .Fn localtime -all take as an argument a time value representing the time in seconds since -the Epoch (00:00:00 -.Tn UTC , -January 1, 1970; see +functions all take as argument a pointer to a time value representing +the time in seconds since the Epoch (00:00:00 UTC on January 1, 1970; +see .Xr time 3 ) . .Pp -The function +The .Fn localtime -converts the time value pointed at by +function converts the time value pointed to by .Fa clock , and returns a pointer to a -.Dq Fa struct tm +.Vt struct tm (described below) which contains the broken-out time information for the value after adjusting for the current -time zone (and any other factors such as Daylight Saving Time). +time zone (see +.Xr tzset 3 ) . When the specified time translates to a year that will not fit in an -.Dv int , +.Vt int , .Fn localtime -returns NULL. -Time zone adjustments are performed as specified by the -.Ev TZ -environment variable (see -.Xr tzset 3 ) . -The function +returns +.Dv NULL . +The .Fn localtime -uses +function uses .Xr tzset 3 to initialize time conversion information if .Xr tzset 3 has not already been called by the process. .Pp -After filling in the tm structure, +After filling in the +.Vt struct tm , .Fn localtime sets the -.Fa tm_isdst Ns 'th +.Va tm_isdst Ns 'th element of -.Fa tzname -to a pointer to an -.Tn ASCII -string that is the time zone abbreviation to be +.Va tzname +to a pointer to an ASCII string that is the time zone abbreviation to be used with .Fn localtime Ns 's return value. .Pp -The function +The .Fn gmtime -similarly converts the time value, but without any time zone adjustment, -and returns a pointer to a tm structure (described below). +function similarly converts the time value, but without any time zone +adjustment, and returns a pointer to a +.Vt struct tm . .Pp The .Fn ctime function adjusts the time value for the current time zone in the same manner as .Fn localtime , and returns a pointer to a 26-character string of the form: .Bd -literal -offset indent Thu Nov 24 18:22:48 1986\en\e0 .Ed .Pp All the fields have constant width. .Pp The +.Fn asctime +function converts the broken down time in the +.Vt struct tm +pointed to by +.Fa tm +to the form shown in the example above. +.Pp +The .Fn ctime_r -function -provides the same functionality as +and +.Fn asctime_r +functions +provide the same functionality as .Fn ctime +and +.Fn asctime except the caller must provide the output buffer -.Fa buf -to store the result, which must be at least 26 characters long. +.Fa buf , +which must be at least 26 characters long, to store the result in. The .Fn localtime_r and .Fn gmtime_r -functions -provide the same functionality as +functions provide the same functionality as .Fn localtime and .Fn gmtime respectively, except the caller must provide the output buffer .Fa result . .Pp -The -.Fn asctime -function -converts the broken down time in the structure -.Fa tm -pointed at by -.Fa *tm -to the form -shown in the example above. -.Pp -The -.Fn asctime_r -function -provides the same functionality as -.Fn asctime -except the caller provide the output buffer -.Fa buf -to store the result, which must be at least 26 characters long. -.Pp The functions .Fn mktime and .Fn timegm -convert the broken-down time in the structure -pointed to by tm into a time value with the same encoding as that of the -values returned by the +convert the broken-down time in the +.Vt struct tm +pointed to by +.Fa tm +into a time value with the same encoding as that of the values +returned by the .Xr time 3 -function (that is, seconds from the Epoch, -.Tn UTC ) . +function (that is, seconds from the Epoch, UTC). The .Fn mktime -function -interprets the input structure according to the current timezone setting -(see -.Xr tzset 3 ) . -The +function interprets the input structure according to the current +timezone setting (see +.Xr tzset 3 ) +while the .Fn timegm -function -interprets the input structure as representing Universal Coordinated Time -.Pq Tn UTC . +function interprets the input structure as representing Universal +Coordinated Time +.Pq UTC . .Pp The original values of the .Fa tm_wday and .Fa tm_yday components of the structure are ignored, and the original values of the other components are not restricted to their normal ranges, and will be normalized if needed. For example, October 40 is changed into November 9, a .Fa tm_hour of \-1 means 1 hour before midnight, .Fa tm_mday of 0 means the day preceding the current month, and .Fa tm_mon of \-2 means 2 months before January of .Fa tm_year . (A positive or zero value for .Fa tm_isdst causes .Fn mktime to presume initially that summer time (for example, Daylight Saving Time) is or is not in effect for the specified time, respectively. A negative value for .Fa tm_isdst causes the .Fn mktime -function to attempt to divine whether summer time is in effect for the +function to attempt to guess whether summer time is in effect for the specified time. The .Fa tm_isdst and .Fa tm_gmtoff members are forced to zero by .Fn timegm . ) .Pp On successful completion, the values of the .Fa tm_wday and .Fa tm_yday components of the structure are set appropriately, and the other components are set to represent the specified calendar time, but with their values forced to their normal ranges; the final value of .Fa tm_mday is not set until .Fa tm_mon and .Fa tm_year are determined. The .Fn mktime function returns the specified calendar time; if the calendar time cannot be represented, it returns \-1; .Pp The .Fn difftime -function -returns the difference between two calendar times, -.Pf ( Fa time1 -- -.Fa time0 ) , -expressed in seconds. +function returns the difference in seconds between two time values, +.Fa time1 +\- +.Fa time0 . .Pp -External declarations as well as the tm structure definition are in the +External declarations as well as the definition of +.Vt struct tm +are in the .In time.h -include file. -The tm structure includes at least the following fields: +header. +The +.Vt tm +structure includes at least the following fields: .Bd -literal -offset indent int tm_sec; /* seconds (0 - 60) */ int tm_min; /* minutes (0 - 59) */ int tm_hour; /* hours (0 - 23) */ int tm_mday; /* day of month (1 - 31) */ int tm_mon; /* month of year (0 - 11) */ int tm_year; /* year \- 1900 */ int tm_wday; /* day of week (Sunday = 0) */ int tm_yday; /* day of year (0 - 365) */ int tm_isdst; /* is summer time in effect? */ char *tm_zone; /* abbreviation of timezone name */ long tm_gmtoff; /* offset from UTC in seconds */ .Ed .Pp The -field .Fa tm_isdst -is non-zero if summer time is in effect. +field is non-zero if summer time is in effect. .Pp -The field +The .Fa tm_gmtoff -is the offset (in seconds) of the time represented from -.Tn UTC , -with positive -values indicating east of the Prime Meridian. +field is the offset in seconds of the time represented from UTC, +with positive values indicating a time zone ahead of UTC (east of the +Prime Meridian). .Sh SEE ALSO .Xr date 1 , .Xr clock_gettime 2 , .Xr gettimeofday 2 , .Xr getenv 3 , .Xr time 3 , .Xr tzset 3 , .Xr tzfile 5 .Sh STANDARDS The .Fn asctime , .Fn ctime , .Fn difftime , .Fn gmtime , .Fn localtime , and .Fn mktime functions conform to .St -isoC , and conform to .St -p1003.1-96 provided the selected local timezone does not contain a leap-second table (see .Xr zic 8 ) . .Pp The .Fn asctime_r , .Fn ctime_r , .Fn gmtime_r , and .Fn localtime_r functions are expected to conform to .St -p1003.1-96 (again provided the selected local timezone does not contain a leap-second table). .Pp The .Fn timegm function is not specified by any standard; its function cannot be completely emulated using the standard functions described above. .Sh HISTORY This manual page is derived from the time package contributed to Berkeley by .An Arthur Olson and which appeared in .Bx 4.3 . .Pp The functions .Fn asctime , .Fn gmtime , and .Fn localtime first appeared in .At v5 , .Fn difftime and .Fn mktime in .Bx 4.3 Reno , and .Fn timegm and .Fn timelocal in SunOS 4.0. .Pp -The functions +The .Fn asctime_r , .Fn ctime_r , -.Fn gmtime_r , +.Fn gmtime_r and .Fn localtime_r -have been available since +functions have been available since .Fx 8.0 . .Sh BUGS Except for .Fn difftime , .Fn mktime , and the .Fn \&_r variants of the other functions, these functions leave their result in an internal static object and return a pointer to that object. Subsequent calls to these function will modify the same object. .Pp The C Standard provides no mechanism for a program to modify its current -local timezone setting, and the -.Tn POSIX Ns No \&-standard +local timezone setting, and the POSIX-standard method is not reentrant. (However, thread-safe implementations are provided -in the -.Tn POSIX -threaded environment.) +in the POSIX threaded environment.) .Pp The .Va tm_zone field of a returned .Vt tm structure points to a static array of characters, which will also be overwritten by any subsequent calls (as well as by subsequent calls to .Xr tzset 3 ) . .Pp Use of the external variable .Fa tzname is discouraged; the .Fa tm_zone entry in the tm structure is preferred.