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<!--Table of Child-Links-->
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<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></A>
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<UL CLASS="ChildLinks">
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<LI><A NAME="tex2html2539"
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HREF="Variable_Expansion.html#SECTION005810000000000000000">General Functionality</A>
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<LI><A NAME="tex2html2540"
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HREF="Variable_Expansion.html#SECTION005820000000000000000">Bacula Variables</A>
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<LI><A NAME="tex2html2541"
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HREF="Variable_Expansion.html#SECTION005830000000000000000">Full Syntax</A>
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<LI><A NAME="tex2html2542"
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HREF="Variable_Expansion.html#SECTION005840000000000000000">Semantics</A>
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<LI><A NAME="tex2html2543"
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HREF="Variable_Expansion.html#SECTION005850000000000000000">Examples</A>
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<!--End of Table of Child-Links-->
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<H1><A NAME="SECTION005800000000000000000"></A>
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<A NAME="VarsChapter"></A>
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Please note that as of version 1.37, the Variable Expansion
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is deprecated and replaced by Python scripting (not yet
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Variable expansion is somewhat similar to Unix shell variable expansion.
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Currently (version 1.31), it is used only in format labels, but in the future,
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it will most likely be used in more places.
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<H1><A NAME="SECTION005810000000000000000">
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General Functionality</A>
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This is basically a string expansion capability that permits referencing
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variables, indexing arrays, conditional replacement of variables, case
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conversion, substring selection, regular expression matching and replacement,
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character class replacement, padding strings, repeated expansion in a user
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controlled loop, support of arithmetic expressions in the loop start, step and
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end conditions, and recursive expansion.
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When using variable expansion characters in a Volume Label Format record, the
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format should always be enclosed in double quotes (<B>"</B>).
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For example, <B>${HOME}</B> will be replaced by your home directory as
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defined in the environment. If you have defined the variable <B>xxx</B> to be
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<B>Test</B>, then the reference <B>${xxx:p/7/Y/r}</B> will right pad the
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contents of <B>xxx</B> to a length of seven characters filling with the
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character <B>Y</B> giving <B>YYYTest</B>.
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<H1><A NAME="SECTION005820000000000000000">
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Within Bacula, there are three main classes of variables with some minor
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variations within the classes. The classes are:
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<DT><STRONG>Counters</STRONG></DT>
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<DD><A NAME="28603"></A>
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Counters are defined by the <B>Counter</B> resources in the Director's conf
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file. The counter can either be a temporary counter that lasts for the
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duration of Bacula's execution, or it can be a variable that is stored in
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the catalog, and thus retains its value from one Bacula execution to another.
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Counter variables may be incremented by postfixing a plus sign (<B>+</B> after
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<DT><STRONG>Internal Variables</STRONG></DT>
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<DD><A NAME="28606"></A>
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Internal variables are read-only, and may be related to the current job (i.e.
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Job name), or maybe special variables such as the date and time. The
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following variables are available:
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<DD>-- the current month 1-12
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<DD>-- the day of the month 1-31
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<DD>-- the current minute 0-59
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<DD>-- the current second 0-59
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<DD>-- the current day of the week 0-6 with 0 being Sunday
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<DD>-- the Director's name
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<DD>-- the unique job name composed of Job and date
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<DD>-- the Storage daemon's name
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<DD>-- the Client's name
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<DD>-- the current number of Volumes in the Pool
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<DD>-- the Catalog name
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<DD>-- the Media Type
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<DT><STRONG>Environment Variables</STRONG></DT>
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<DD><A NAME="28609"></A>
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Environment variables are read-only, and must be defined in the environment
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prior to executing Bacula. Environment variables may be either scalar or an
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array, where the elements of the array are referenced by subscripting the
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variable name (e.g. <B>${Months[3]}</B>). Environment variable arrays are
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defined by separating the elements with a vertical bar (<B>|</B>), thus <B>set Months="Jan|Feb|Mar|Apr|..."</B> defines an environment variable named
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<B>Month</B> that will be treated as an array, and the reference <B>${Months[3]}</B> will yield <B>Mar</B>. The elements of the array can have
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<H1><A NAME="SECTION005830000000000000000">
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Since the syntax is quite extensive, below, you will find the pseudo BNF. The
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special characters have the following meaning:
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( ) grouping if the parens are not quoted
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| separates alternatives
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'/' literal / (or any other character)
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CAPS a character or character sequence
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* preceding item can be repeated zero or more times
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? preceding item can appear zero or one time
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+ preceding item must appear one or more times
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And the pseudo BNF describing the syntax is:
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| INDEX_OPEN input INDEX_CLOSE (loop_limits)?
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variable ::= DELIM_INIT (name|expression)
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name ::= (NAME_CHARS)+
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expression ::= DELIM_OPEN
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(INDEX_OPEN num_exp INDEX_CLOSE)?
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command ::= '-' (TEXT_EXP|variable)+
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| '+' (TEXT_EXP|variable)+
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| 'o' NUMBER ('-'|',') (NUMBER)?
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| '*' (TEXT_EXP|variable)+
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| 's' '/' (TEXT_PATTERN)+
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'/' (variable|TEXT_SUBST)*
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'/' ('m'|'g'|'i'|'t')*
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| 'y' '/' (variable|TEXT_SUBST)+
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'/' (variable|TEXT_SUBST)*
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'/' (variable|TEXT_SUBST)*
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| '%' (name|variable)+
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('(' (TEXT_ARGS)? ')')?
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| operand ('+'|'-'|'*'|'/'|'%') num_exp
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operand ::= ('+'|'-')? NUMBER
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loop_limits ::= DELIM_OPEN
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(num_exp)? ',' (num_exp)? (',' (num_exp)?)?
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NUMBER ::= ('0'|...|'9')+
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TEXT_PATTERN::= (^('/'))+
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TEXT_SUBST ::= (^(DELIM_INIT|'/'))+
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TEXT_ARGS ::= (^(DELIM_INIT|')'))+
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TEXT_EXP ::= (^(DELIM_INIT|DELIM_CLOSE|':'|'+'))+
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TEXT ::= (^(DELIM_INIT|INDEX_OPEN|INDEX_CLOSE))+
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NAME_CHARS ::= 'a'|...|'z'|'A'|...|'Z'|'0'|...|'9'
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<H1><A NAME="SECTION005840000000000000000">
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The items listed in <B>command</B> above, which always follow a colon (<B>:</B>)
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have the following meanings:
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- perform substitution if variable is empty
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+ perform substitution if variable is not empty
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o cut out substring of the variable value
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# length of the variable value
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* substitute empty string if the variable value is not empty,
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otherwise substitute the trailing parameter
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s regular expression search and replace. The trailing
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options are: m = multiline, i = case insensitive,
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g = global, t = plain text (no regexp)
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y transpose characters from class A to class B
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p pad variable to l = left, r = right or c = center,
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% special function call (none implemented)
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l lower case the variable value
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u upper case the variable value
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The <B>loop_limits</B> are start, step, and end values.
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A counter variable name followed immediately by a plus (<B>+</B>) will cause
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the counter to be incremented by one.
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<H1><A NAME="SECTION005850000000000000000">
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To create an ISO date:
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DLT-${Year}-${Month:p/2/0/r}-${Day:p/2/0/r}
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on 20 June 2003 would give <B>DLT-2003-06-20</B>
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If you set the environment variable <B>mon</B> to
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January|February|March|April|May|...
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File-${mon[${Month}]}/${Day}/${Year}
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on the first of March would give <B>File-March/1/2003 </B>
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