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authordkf <donal.k.fellows@manchester.ac.uk>2009-02-24 21:04:58 (GMT)
committerdkf <donal.k.fellows@manchester.ac.uk>2009-02-24 21:04:58 (GMT)
commitd24c35f276199a428012749034360a0ab17c00da (patch)
treebd89a06d093bc6aed00d0c588a506836a2576c5c /doc/clock.n
parentb51f251bd053d6532d178b3f1b101d5cfd15f610 (diff)
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General minor documentation improvements.
Diffstat (limited to 'doc/clock.n')
-rw-r--r--doc/clock.n9
1 files changed, 9 insertions, 0 deletions
diff --git a/doc/clock.n b/doc/clock.n
index f4c3805..56a139e 100644
--- a/doc/clock.n
+++ b/doc/clock.n
@@ -161,12 +161,14 @@ the environment variable \fBTZ\fR.
.IP [3]
on Windows systems, the time zone settings from the Control Panel.
.RE
+.PP
If none of these is present, the C \fBlocaltime\fR and \fBmktime\fR
functions are used to attempt to convert times between local and
Greenwich. On 32-bit systems, this approach is likely to have bugs,
particularly for times that lie outside the window (approximately the
years 1902 to 2037) that can be represented in a 32-bit integer.
.SH "CLOCK ARITHMETIC"
+.PP
The \fBclock add\fR command performs clock arithmetic on a value
(expressed as nominal seconds from the epoch time of 1 January 1970, 00:00 UTC)
given as its first argument. The remaining arguments (other than the
@@ -275,6 +277,7 @@ years as they are when adding/subtracting days and weeks.
If multiple \fIcount unit\fR pairs are present on the command, they
are evaluated consecutively, from left to right.
.SH "HIGH RESOLUTION TIMERS"
+.PP
Most of the subcommands supported by the \fBclock\fR command deal with
times represented as a count of seconds from the epoch time, and this is the
representation that \fBclock seconds\fR returns. There are three exceptions,
@@ -289,6 +292,7 @@ epoch; it is simply intended to be the most precise interval timer
available, and is intended only for relative timing studies such as
benchmarks.
.SH "FORMATTING TIMES"
+.PP
The \fBclock format\fR command produces times for display to a user
or writing to an external medium. The command accepts times that are
expressed in seconds from the epoch time of 1 January 1970, 00:00 UTC,
@@ -327,6 +331,7 @@ platforms that do not define a user selection of date and time formats
separate from \fBLC_TIME\fR, \fB\-locale\fR \fBsystem\fR is
synonymous with \fB\-locale\fR \fBcurrent\fR.
.SH "SCANNING TIMES"
+.PP
The \fBclock scan\fR command accepts times that are formatted as
strings and converts them to counts of seconds from the epoch time
of 1 January 1970, 00:00 UTC. It normally takes a \fB\-format\fR
@@ -449,6 +454,7 @@ If this situation occurs, the first occurrence of the time is chosen.
time zone when converting local times. This caveat does not apply to
UTC times.)
.SH "FORMAT GROUPS"
+.PP
The following format groups are recognized by the \fBclock scan\fR and
\fBclock format\fR commands.
.TP
@@ -738,6 +744,7 @@ character.
Synonymous with
.QW "\fB%a %b %e %H:%M:%S %Z %Y\fR" .
.SH "TIME ZONES"
+.PP
When the \fBclock\fR command is processing a local time, it has several
possible sources for the time zone to use. In order of preference, they
are:
@@ -825,10 +832,12 @@ rules change again.
Any other time zone string is processed by prefixing a colon and attempting
to use it as a location name, as above.
.SH "LOCALIZATION"
+.PP
Developers wishing to localize the date and time formatting and parsing
are referred to \fIhttp://tip.tcl.tk/173\fR for a
specification.
.SH "FREE FORM SCAN"
+.PP
If the \fBclock scan\fR command is invoked without a \fB\-format\fR
option, then it requests a \fIfree-form scan.\fR \fI
This form of scan is deprecated.\fR The reason for the deprecation