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| -rw-r--r-- | man5/tzfile.5 | 72 |
1 files changed, 69 insertions, 3 deletions
diff --git a/man5/tzfile.5 b/man5/tzfile.5 index 771bfd2d1e..be09f303f8 100644 --- a/man5/tzfile.5 +++ b/man5/tzfile.5 @@ -20,7 +20,7 @@ Timezone information files begin with the magic characters "TZif" to identify them as timezone information files, followed by a character identifying the version of the file's format -(as of 2005, either an ASCII NUL (\(aq\\0\(aq) or a \(aq2\(aq) +(as of 2005, either an ASCII NUL (\(aq\\0\(aq) or a \(aq2\(aq (\fB0x32\fP)) followed by fifteen bytes containing zeros reserved for future use, followed by six four-byte values of type .IR long , @@ -144,16 +144,82 @@ if either .I tzh_timecnt is zero or the time argument is less than the first transition time recorded in the file. -.PP +.SS Version 2 format For version-2-format timezone files, the above header and data is followed by a second header and data, identical in format except that -eight bytes are used for each transition time or leap-second time. +eight bytes are used for each transition time or leap-second time +(and that the version byte in the header record is +\fB0x32\fP rather than \fB0x00\fP). After the second header and data comes a newline-enclosed, POSIX-TZ-environment-variable-style string for use in handling instants after the last transition time stored in the file (with nothing between the newlines if there is no POSIX representation for such instants). +.PP +The second section of the timezone file consists of another 44-byte header +record, identical in structure to the one at the beginning of the file, +except that it applies to the data that follows, +which is also identical in structure +to the first section of the timezone file, with the following differences: +.IP * 3 +The transition time values, after the header, are eight-byte values. +.IP * +In each leap second record, the leap second value is an eight-byte value. +The accumulated leap second count is still a four-byte value. +.PP +In all cases, the eight-byte time values are given in +the "standard" byte order, +the high-order byte first. +.SS POSIX timezone string +The second eight-byte time value section is followed by an optional +third section: +a single ASCII newline character (\(aq\\n\(aq), +then a text string followed by a second +newline character. +The text string is a POSIX timezone string, whose format is described in the +.BR tzset (3) +manual page. +.PP +The POSIX timezone string defines a rule for computing transition times +that follow the last transition time explicitly specified in the timezone +information file. +.SS Summary of the timezone information file format +\& +.sp 2 +.RS +.nf +Four-byte value section +(header version \fB0x00\fP or \fB0x32\fP) + Header record + Four-byte transition times + Transition time index + \fBttinfo\fP structures + Timezone abbreviation array + Leap second records + Standard/Wall array + UTC/Local array + +Eight-byte value section +(only if first header version is \fB0x32\fP, +the second header's version is also \fB0x32\fP) + Header record + Eight-byte transition times + Transition time index + \fBttinfo\fP structures + Timezone abbreviation array + Leap second records + Standard/Wall array + UTC/Local array + +Third section +(optional, only in \fB0x32\fP version files) + Newline character + Timezone string + Newline character +.fi +.RE + .SH SEE ALSO .BR ctime (3), .BR tzset (3), |