4 \chapter{Variable Expansion}
6 \index[general]{Variable Expansion }
7 \index[general]{Expansion!Variable }
9 % TODO: does the following mean that this should not be in book?
11 Please note that as of version 1.37, the Variable Expansion
12 is deprecated and replaced by Python scripting (not yet
15 Variable expansion is somewhat similar to Unix shell variable expansion.
16 Currently (version 1.31), it is used only in format labels, but in the future,
17 it will most likely be used in more places.
19 \section{General Functionality}
20 \index[general]{Functionality!General }
21 \index[general]{General Functionality }
23 This is basically a string expansion capability that permits referencing
24 variables, indexing arrays, conditional replacement of variables, case
25 conversion, substring selection, regular expression matching and replacement,
26 character class replacement, padding strings, repeated expansion in a user
27 controlled loop, support of arithmetic expressions in the loop start, step and
28 end conditions, and recursive expansion.
30 When using variable expansion characters in a Volume Label Format record, the
31 format should always be enclosed in double quotes ({\bf "}).
33 For example, {\bf \$\{HOME\}} will be replaced by your home directory as
34 defined in the environment. If you have defined the variable {\bf xxx} to be
35 {\bf Test}, then the reference {\bf \$\{xxx:p/7/Y/r\}} will right pad the
36 contents of {\bf xxx} to a length of seven characters filling with the
37 character {\bf Y} giving {\bf YYYTest}.
39 \section{Bacula Variables}
40 \index[general]{Bacula Variables }
41 \index[general]{Variables!Bacula }
43 Within Bacula, there are three main classes of variables with some minor
44 variations within the classes. The classes are:
49 \index[dir]{Counters }
50 Counters are defined by the {\bf Counter} resources in the Director's conf
51 file. The counter can either be a temporary counter that lasts for the
52 duration of Bacula's execution, or it can be a variable that is stored in
53 the catalog, and thus retains its value from one Bacula execution to another.
54 Counter variables may be incremented by postfixing a plus sign ({\bf +} after
57 \item [Internal Variables]
58 \index[dir]{Internal Variables }
59 Internal variables are read-only, and may be related to the current job (i.e.
60 Job name), or maybe special variables such as the date and time. The
61 following variables are available:
64 \item [Year] -- the full year
65 \item [Month] -- the current month 1-12
66 \item [Day] -- the day of the month 1-31
67 \item [Hour] -- the hour 0-24
68 \item [Minute] -- the current minute 0-59
69 \item [Second] -- the current second 0-59
70 \item [WeekDay] -- the current day of the week 0-6 with 0 being Sunday
71 \item [Job] -- the job name
72 \item [Dir] -- the Director's name
73 \item [Level] -- the Job Level
74 \item [Type] -- the Job type
75 \item [JobId] -- the JobId
76 \item [JobName] -- the unique job name composed of Job and date
77 \item [Storage] -- the Storage daemon's name
78 \item [Client] -- the Client's name
79 \item [NumVols] -- the current number of Volumes in the Pool
80 \item [Pool] -- the Pool name
81 \item [Catalog] -- the Catalog name
82 \item [MediaType] -- the Media Type
85 \item [Environment Variables]
86 \index[dir]{Environment Variables }
87 Environment variables are read-only, and must be defined in the environment
88 prior to executing Bacula. Environment variables may be either scalar or an
89 array, where the elements of the array are referenced by subscripting the
90 variable name (e.g. {\bf \$\{Months[3]\}}). Environment variable arrays are
91 defined by separating the elements with a vertical bar ({\bf |}), thus {\bf
92 set Months="Jan|Feb|Mar|Apr|..."} defines an environment variable named
93 {\bf Month} that will be treated as an array, and the reference {\bf
94 \$\{Months[3]\}} will yield {\bf Mar}. The elements of the array can have
99 \index[general]{Syntax!Full }
100 \index[general]{Full Syntax }
102 Since the syntax is quite extensive, below, you will find the pseudo BNF. The
103 special characters have the following meaning:
108 ( ) grouping if the parens are not quoted
109 | separates alternatives
110 '/' literal / (or any other character)
111 CAPS a character or character sequence
112 * preceding item can be repeated zero or more times
113 ? preceding item can appear zero or one time
114 + preceding item must appear one or more times
118 And the pseudo BNF describing the syntax is:
124 | INDEX_OPEN input INDEX_CLOSE (loop_limits)?
126 variable ::= DELIM_INIT (name|expression)
127 name ::= (NAME_CHARS)+
128 expression ::= DELIM_OPEN
130 (INDEX_OPEN num_exp INDEX_CLOSE)?
133 command ::= '-' (TEXT_EXP|variable)+
134 | '+' (TEXT_EXP|variable)+
135 | 'o' NUMBER ('-'|',') (NUMBER)?
137 | '*' (TEXT_EXP|variable)+
138 | 's' '/' (TEXT_PATTERN)+
139 '/' (variable|TEXT_SUBST)*
140 '/' ('m'|'g'|'i'|'t')*
141 | 'y' '/' (variable|TEXT_SUBST)+
142 '/' (variable|TEXT_SUBST)*
145 '/' (variable|TEXT_SUBST)*
147 | '%' (name|variable)+
148 ('(' (TEXT_ARGS)? ')')?
152 | operand ('+'|'-'|'*'|'/'|'%') num_exp
153 operand ::= ('+'|'-')? NUMBER
157 loop_limits ::= DELIM_OPEN
158 (num_exp)? ',' (num_exp)? (',' (num_exp)?)?
160 NUMBER ::= ('0'|...|'9')+
161 TEXT_PATTERN::= (^('/'))+
162 TEXT_SUBST ::= (^(DELIM_INIT|'/'))+
163 TEXT_ARGS ::= (^(DELIM_INIT|')'))+
164 TEXT_EXP ::= (^(DELIM_INIT|DELIM_CLOSE|':'|'+'))+
165 TEXT ::= (^(DELIM_INIT|INDEX_OPEN|INDEX_CLOSE))+
172 NAME_CHARS ::= 'a'|...|'z'|'A'|...|'Z'|'0'|...|'9'
177 \index[general]{Semantics }
179 The items listed in {\bf command} above, which always follow a colon ({\bf :})
180 have the following meanings:
184 - perform substitution if variable is empty
185 + perform substitution if variable is not empty
186 o cut out substring of the variable value
187 # length of the variable value
188 * substitute empty string if the variable value is not empty,
189 otherwise substitute the trailing parameter
190 s regular expression search and replace. The trailing
191 options are: m = multiline, i = case insensitive,
192 g = global, t = plain text (no regexp)
193 y transpose characters from class A to class B
194 p pad variable to l = left, r = right or c = center,
196 % special function call (none implemented)
197 l lower case the variable value
198 u upper case the variable value
202 The {\bf loop\_limits} are start, step, and end values.
204 A counter variable name followed immediately by a plus ({\bf +}) will cause
205 the counter to be incremented by one.
208 \index[general]{Examples }
210 To create an ISO date:
214 DLT-${Year}-${Month:p/2/0/r}-${Day:p/2/0/r}
218 on 20 June 2003 would give {\bf DLT-2003-06-20}
220 If you set the environment variable {\bf mon} to
224 January|February|March|April|May|...
225 File-${mon[${Month}]}/${Day}/${Year}
229 on the first of March would give {\bf File-March/1/2003 }