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author | 2021-05-09 14:20:58 -0400 | |
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committer | 2021-05-09 14:20:58 -0400 | |
commit | 5fd83771641d15c418f747bd343ba6738d3875f7 (patch) | |
tree | 5abf0f78f680d9837dbd93d4d4c3933bb7509599 /shell_cmds/date/date.1 | |
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Import macOS userland
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Diffstat (limited to 'shell_cmds/date/date.1')
-rw-r--r-- | shell_cmds/date/date.1 | 472 |
1 files changed, 472 insertions, 0 deletions
diff --git a/shell_cmds/date/date.1 b/shell_cmds/date/date.1 new file mode 100644 index 0000000..0cabb01 --- /dev/null +++ b/shell_cmds/date/date.1 @@ -0,0 +1,472 @@ +.\"- +.\" Copyright (c) 1980, 1990, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" This code is derived from software contributed to Berkeley by +.\" the Institute of Electrical and Electronics Engineers, Inc. +.\" +.\" 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. +.\" 4. 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. +.\" +.\" @(#)date.1 8.3 (Berkeley) 4/28/95 +.\" $FreeBSD$ +.\" +.Dd May 7, 2015 +.Dt DATE 1 +.Os +.Sh NAME +.Nm date +.Nd display or set date and time +.Sh SYNOPSIS +.Nm +.Op Fl jRu +.Op Fl r Ar seconds | Ar filename +.Oo +.Fl v +.Sm off +.Op Cm + | - +.Ar val Op Ar ymwdHMS +.Sm on +.Oc +.Ar ... +.Op Cm + Ns Ar output_fmt +.Nm +.Op Fl jnu +.Sm off +.Op Oo Oo Ar mm Oc Ar dd Oc Ar HH +.Ar MM Oo Oo Ar cc Oc Ar yy Oc Op Ar .ss +.Sm on +.Nm +.Op Fl jnRu +.Fl f Ar input_fmt new_date +.Op Cm + Ns Ar output_fmt +.Nm +.Op Fl d Ar dst +.Op Fl t Ar minutes_west +.Sh DESCRIPTION +When invoked without arguments, the +.Nm +utility displays the current date and time. +Otherwise, depending on the options specified, +.Nm +will set the date and time or print it in a user-defined way. +.Pp +The +.Nm +utility displays the date and time read from the kernel clock. +When used to set the date and time, +both the kernel clock and the hardware clock are updated. +.Pp +Only the superuser may set the date, +and if the system securelevel (see +.Xr securelevel 7 ) +is greater than 1, +the time may not be changed by more than 1 second. +.Pp +The options are as follows: +.Bl -tag -width Ds +.It Fl d Ar dst +Set the kernel's value for daylight saving time. +If +.Ar dst +is non-zero, future calls +to +.Xr gettimeofday 2 +will return a non-zero for +.Fa tz_dsttime . +.It Fl f +Use +.Ar input_fmt +as the format string to parse the +.Ar new_date +provided rather than using the default +.Sm off +.Oo Oo Oo +.Ar mm Oc +.Ar dd Oc +.Ar HH Oc +.Ar MM +.Oo Oo +.Ar cc Oc +.Ar yy Oc Oo +.Ar .ss Oc +.Sm on +format. +Parsing is done using +.Xr strptime 3 . +.It Fl j +Do not try to set the date. +This allows you to use the +.Fl f +flag in addition to the +.Cm + +option to convert one date format to another. +.It Fl n +By default, if the +.Xr timed 8 +daemon is running, +.Nm +sets the time on all of the machines in the local group. +The +.Fl n +option suppresses this behavior and causes the time to be set only on the +current machine. +.It Fl R +Use RFC 2822 date and time output format. This is equivalent to use +.Dq Li %a, %d %b %Y \&%T %z +as +.Ar output_fmt +while +.Ev LC_TIME +is set to the +.Dq C +locale . +.It Fl r Ar seconds +Print the date and time represented by +.Ar seconds , +where +.Ar seconds +is the number of seconds since the Epoch +(00:00:00 UTC, January 1, 1970; +see +.Xr time 3 ) , +and can be specified in decimal, octal, or hex. +.It Fl r Ar filename +Print the date and time of the last modification of +.Ar filename . +.It Fl t Ar minutes_west +Set the system's value for minutes west of +.Tn GMT . +.Ar minutes_west +specifies the number of minutes returned in +.Fa tz_minuteswest +by future calls to +.Xr gettimeofday 2 . +.It Fl u +Display or set the date in +.Tn UTC +(Coordinated Universal) time. +.It Fl v +Adjust (i.e., take the current date and display the result of the +adjustment; not actually set the date) the second, minute, hour, month +day, week day, month or year according to +.Ar val . +If +.Ar val +is preceded with a plus or minus sign, +the date is adjusted forwards or backwards according to the remaining string, +otherwise the relevant part of the date is set. +The date can be adjusted as many times as required using these flags. +Flags are processed in the order given. +.Pp +When setting values +(rather than adjusting them), +seconds are in the range 0-59, minutes are in the range 0-59, hours are +in the range 0-23, month days are in the range 1-31, week days are in the +range 0-6 (Sun-Sat), +months are in the range 1-12 (Jan-Dec) +and years are in the range 80-38 or 1980-2038. +.Pp +If +.Ar val +is numeric, one of either +.Ar y , +.Ar m , +.Ar w , +.Ar d , +.Ar H , +.Ar M +or +.Ar S +must be used to specify which part of the date is to be adjusted. +.Pp +The week day or month may be specified using a name rather than a +number. +If a name is used with the plus +(or minus) +sign, the date will be put forwards +(or backwards) +to the next +(previous) +date that matches the given week day or month. +This will not adjust the date, +if the given week day or month is the same as the current one. +.Pp +When a date is adjusted to a specific value or in units greater than hours, +daylight savings time considerations are ignored. +Adjustments in units of hours or less honor daylight saving time. +So, assuming the current date is March 26, 0:30 and that the DST adjustment +means that the clock goes forward at 01:00 to 02:00, using +.Fl v No +1H +will adjust the date to March 26, 2:30. +Likewise, if the date is October 29, 0:30 and the DST adjustment means that +the clock goes back at 02:00 to 01:00, using +.Fl v No +3H +will be necessary to reach October 29, 2:30. +.Pp +When the date is adjusted to a specific value that does not actually exist +(for example March 26, 1:30 BST 2000 in the Europe/London timezone), +the date will be silently adjusted forwards in units of one hour until it +reaches a valid time. +When the date is adjusted to a specific value that occurs twice +(for example October 29, 1:30 2000), +the resulting timezone will be set so that the date matches the earlier of +the two times. +.Pp +It is not possible to adjust a date to an invalid absolute day, so using +the switches +.Fl v No 31d Fl v No 12m +will simply fail five months of the year. +It is therefore usual to set the month before setting the day; using +.Fl v No 12m Fl v No 31d +always works. +.Pp +Adjusting the date by months is inherently ambiguous because +a month is a unit of variable length depending on the current date. +This kind of date adjustment is applied in the most intuitive way. +First of all, +.Nm +tries to preserve the day of the month. +If it is impossible because the target month is shorter than the present one, +the last day of the target month will be the result. +For example, using +.Fl v No +1m +on May 31 will adjust the date to June 30, while using the same option +on January 30 will result in the date adjusted to the last day of February. +This approach is also believed to make the most sense for shell scripting. +Nevertheless, be aware that going forth and back by the same number of +months may take you to a different date. +.Pp +Refer to the examples below for further details. +.El +.Pp +An operand with a leading plus +.Pq Sq + +sign signals a user-defined format string +which specifies the format in which to display the date and time. +The format string may contain any of the conversion specifications +described in the +.Xr strftime 3 +manual page, as well as any arbitrary text. +A newline +.Pq Ql \en +character is always output after the characters specified by +the format string. +The format string for the default display is +.Dq +%+ . +.Pp +If an operand does not have a leading plus sign, it is interpreted as +a value for setting the system's notion of the current date and time. +The canonical representation for setting the date and time is: +.Pp +.Bl -tag -width Ds -compact -offset indent +.It Ar cc +Century +(either 19 or 20) +prepended to the abbreviated year. +.It Ar yy +Year in abbreviated form +(e.g., 89 for 1989, 06 for 2006). +.It Ar mm +Numeric month, a number from 1 to 12. +.It Ar dd +Day, a number from 1 to 31. +.It Ar HH +Hour, a number from 0 to 23. +.It Ar MM +Minutes, a number from 0 to 59. +.It Ar ss +Seconds, a number from 0 to 61 +(59 plus a maximum of two leap seconds). +.El +.Pp +Everything but the minutes is optional. +.Pp +Time changes for Daylight Saving Time, standard time, leap seconds, +and leap years are handled automatically. +.Sh ENVIRONMENT +The following environment variables affect the execution of +.Nm : +.Bl -tag -width Ds +.It Ev TZ +The timezone to use when displaying dates. +The normal format is a pathname relative to +.Pa /usr/share/zoneinfo . +For example, the command +.Dq TZ=America/Los_Angeles date +displays the current time in California. +See +.Xr environ 7 +for more information. +.El +.Sh FILES +.Bl -tag -width /var/log/messages -compact +.It Pa /var/log/messages +record of the user setting the time +.El +.Sh EXIT STATUS +The +.Nm +utility exits 0 on success, 1 if unable to set the date, and 2 +if able to set the local date, but unable to set it globally. +.Sh EXAMPLES +The command: +.Pp +.Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S""" +.Pp +will display: +.Bd -literal -offset indent +DATE: 1987-11-21 +TIME: 13:36:16 +.Ed +.Pp +In the Europe/London timezone, the command: +.Pp +.Dl "date -v1m -v+1y" +.Pp +will display: +.Pp +.Dl "Sun Jan 4 04:15:24 GMT 1998" +.Pp +where it is currently +.Li "Mon Aug 4 04:15:24 BST 1997" . +.Pp +The command: +.Pp +.Dl "date -v1d -v3m -v0y -v-1d" +.Pp +will display the last day of February in the year 2000: +.Pp +.Dl "Tue Feb 29 03:18:00 GMT 2000" +.Pp +So will the command: +.Pp +.Dl "date -v3m -v30d -v0y -v-1m" +.Pp +because there is no such date as the 30th of February. +.Pp +The command: +.Pp +.Dl "date -v1d -v+1m -v-1d -v-fri" +.Pp +will display the last Friday of the month: +.Pp +.Dl "Fri Aug 29 04:31:11 BST 1997" +.Pp +where it is currently +.Li "Mon Aug 4 04:31:11 BST 1997" . +.Pp +The command: +.Pp +.Dl "date 0613162785" +.Pp +sets the date to +.Dq Li "June 13, 1985, 4:27 PM" . +.Pp +.Dl "date ""+%m%d%H%M%Y.%S""" +.Pp +may be used on one machine to print out the date +suitable for setting on another. +.Pp +The command: +.Pp +.Dl "date 1432" +.Pp +sets the time to +.Li "2:32 PM" , +without modifying the date. +.Pp +Finally the command: +.Pp +.Dl "date -j -f ""%a %b %d %T %Z %Y"" ""`date`"" ""+%s""" +.Pp +can be used to parse the output from +.Nm +and express it in Epoch time. +.Sh DIAGNOSTICS +Occasionally, when +.Xr timed 8 +synchronizes the time on many hosts, the setting of a new time value may +require more than a few seconds. +On these occasions, +.Nm +prints: +.Ql Network time being set . +The message +.Ql Communication error with timed +occurs when the communication +between +.Nm +and +.Xr timed 8 +fails. +.Sh LEGACY SYNOPSIS +As above, except for the second line, which is: +.Pp +.Nm +.Op Fl jnu +.Sm off +.Op Oo Oo Oo Oo Ar cc Oc Ar yy Oc Ar mm Oc Ar dd Oc Ar HH +.Ar MM Op Ar .ss +.Sm on +.Sh LEGACY DIAGNOSTICS +When invoked in legacy mode, the following exit values are returned: +.Bl -tag -width X -compact +.It 0 +The date was written successfully +.It 1 +Unable to set the date +.It 2 +Able to set the local date, but unable to set it globally +.El +.Pp +For more information about legacy mode, see +.Xr compat 5 . +.Sh SEE ALSO +.Xr locale 1 , +.Xr gettimeofday 2 , +.Xr getutxent 3 , +.Xr strftime 3 , +.Xr strptime 3 , +.Xr timed 8 +.Rs +.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD" +.%A R. Gusella +.%A S. Zatti +.Re +.Sh STANDARDS +The +.Nm +utility is expected to be compatible with +.St -p1003.2 . +The +.Fl d , f , j , n , r , t , +and +.Fl v +options are all extensions to the standard. +.Sh HISTORY +A +.Nm +command appeared in +.At v1 . |