Linux Command Directory


Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

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zic

zic [options] [files]

System administration command. Create time conversion information files from the file or files specified. If the specified file is -, read information from standard input.

Options

-d directory

Place the newly created files in directory. Default is /usr/local/etc/zoneinfo.

-l timezone

Specify a timezone to use for local time. zic links the zone information for timezone with the zone localtime.

-p timezone

Set the default rules for handling POSIX-format environment variables to the zone name specified by timezone.

-s

Store time values only if they are the same when signed as when unsigned.

-v

Verbose mode. Include extra error checking and warnings.

-y command

Check year types with command. Default is yearistype.

-L file

Consult file for information about leap seconds.

The source files for zic should be formatted as a sequence of rule lines, zone lines, and link lines. An optional file containing leap-second rules can be specified on the command line. Rule lines describe how time should be calculated. They describe changes in time, daylight savings time, and any other changes that might affect a particular time zone. Zone lines specify which rules apply to a given zone. Link lines link similar zones together. Leap lines describe the exact time when leap seconds should be added or subtracted. Each of these lines is made up of fields. Fields are separated from one another by any number of whitespace characters. Comment lines are preceded by #. The fields used in each line are listed in the next section.

Rule line fields

The format of a rule line is:

Rule NAME FROM TO TYPE IN ON AT SAVE LETTERS

NAME

Name this set of rules.

FROM

Specify the first year to which this rule applies. Gregorian calendar dates are assumed. Instead of specifying an actual year, you may specify minimum or maximum for the minimum or maximum year, representable as an integer.

TO

Specify the last year to which this rule applies. Syntax is the same as for the FROM field.

TYPE

Specify the type of year to which this rule should be applied. The wildcard - instructs that all years be included. Any given year's type will be checked with the command given with the -y option or the default yearistype year type. An exit status of 0 is taken to mean the year is of the given type; an exit status of 1 means that it is not of the given type (see -y option).

IN

Specify month in which this rule should be applied.

ON

Specify day on which this rule should be applied. Whitespace is not allowed. For example:

1

The 1st.

firstSun

The first Sunday.

Sun>=3

The first Sunday to occur before or on the 3rd.

AT

Specify the time after which the rule is in effect. For example, you may use 13, 13:00, or 13:00:00 for 1:00 p.m. You may include one of several suffixes (without whitespace between):

s

Local standard time.

u, g, z

Universal time.

w

Wall clock time (default).

SAVE

Add this amount of time to the local standard time. Formatted like AT, without suffixes.

LETTERS

Specify letter or letters to be used in time zone abbreviations (for example, S for EST). For no abbreviation, enter -.

Zone line fields

The format of a zone line is:

Zone NAME GMTOFF RULES/SAVE FORMAT [UNTIL]

NAME

Time zone name.

GMTOFF

The amount of hours by which this time zone differs from GMT. Formatted like AT. Negative times are subtracted from GMT; by default, times are added to it.

RULES/SAVE

Either the name of the rule to apply to this zone or the amount of time to add to local standard time. To make the zone the same as local standard time, specify -.

FORMAT

The format of time zone abbreviations. Specify the variable part with %s.

UNTIL

Change the rule for the zone at this date. The next line must specify the new zone information and therefore must omit the string "Zone" and the NAME field.

Link line fields

The format of a link line is:

Link LINK-FROM LINK-TO

LINK-FROM

The name of the zone that is being linked.

LINK-TO

An alternate name for the zone that was specified as LINK-FROM.

Leap line fields

The format of a leap line is:

Leap YEAR MONTH DAY HH:MM:SS CORR R|S

YEAR MONTH DAY HH:MM:SS

Specify when the leap second happened.

CORR

Uses + or - to show whether the second was added or skipped.

R|S

Rolling or Stationary. Describe whether the leap second should be applied to local wall-clock time or GMT, respectively.


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