Variables

xmlsh variables can be either strings or XML types (infoset, including sequences).
There is no limit to the size of variables besides JVM memory.
Variables are created using variable assignment (Variables). The type of the expression determins
if a variable is a string or XML variable. Variables can be re-assigned and this can change their type.

Example of string assignments
A=string
A="string"
A='string'
B="another $A"
C=${B}
D=$(echo yet more strings)
E=$(ls)


Example of XML assignments
A=<[<foo/>]>
A=<[1,2,3,<foo>bar</foo>]>
A=$<(xls)
DOC=<[<foo><bar>text</bar></foo>]>
T=<[<spam>{$DOC//bar}</spam>]>


Sequence Construction

Variable assignment supports a simplified sequence expression, similar to bash and ksh array assignment.
var=(elem elem ...)

For example
$ var=(foo bar spam)

Assigns an XML sequence of strings equivilent to 
$ var=<[("foo","bar","spam")]>


The values inside () are expanded using Word expansion and Globbing before being assigned.
Note that this is different then non-sequence construction which doesn't do globbing (wildcard expansion).
Assuming there are 21 xml files in the current directory
$ var=(*.xml)
$ echo <[ count($var) ]>
21
$ var=*.xml
$ echo <[ count($var) ]>
1


Assigns var to be the sequence containing all xml files in the current directory.

The empty sequence construct creates an empty sequence. This is different then string assignment which creates a empty string.

var=()
echo <[count($var)]>

returns
0


var=""
echo <[count($var)]>

Returns
1


Sequence Append

Sequences can be appended using the syntax
VAR+=value

This is a syntax shortcut for 
VAR=($VAR,value)

or
VAR=<[ $VAR , value ]>


If the variable doesn't exist it is created as if assigned using =.



Example: Create a sequence of integers 1 to 10 then append 20 to 30
A=<[ 1 to 10 ]>
A+=<[ 20 to 30 ]>
echo $A

Result
1 2 3 4 5 6 7 8 9 10 20 21 22 23 24 25 26 27 28 29 30


Example Create an element then append to it
A=<[ <foo>text</foo> ]>
A+=<[ <bar>text</bar> ]>
xecho $A


Result
<foo>text</foo>
<bar>text</bar>







Array Notation

xmlsh supports a simplified version of the bash array notation in variable expansion.

The expression ${variable[index]} expands to the index'd element of a sequence variable. Index starts at 1 for compatibility with xpath expressions. ${variable[index]} is equivalent to <[ $variable[index] ]>.

The expression ${#variable} expands to the sequence length of variable. ${#variable} is equivalent to <[ count($variable) ]>

A non-sequenced variable is equivalent to a sequenced variable of length 1.

Unlike bash, sparse arrays are not supported because array notation is just a syntactic simplification over the XML infoset sequence variables which cannot be sparse.

Examples

var=(foo bar spam)
echo ${#var}
echo ${var[2]}

returns
3
bar


var=<[ "foo" , <spam attr="bar"><bletch>text</bletch></spam> , 1  , 2 , 3 ]>
echo ${#var}
xecho ${var[2]}

returns
5
<spam attr="bar"><bletch>text</bletch></spam>



Tied Variables


See the tie command for how to tie xquery expressions to variables.



See Also Basic Syntax
See Also tie
See Also Builtin Variables
Comments [Hide comments]
Comment by JeffIshaq
2009-05-04 18:50:56
To document: Example of XML variable types (such as assigning 'true' to a temporary bElementWasProcessed varaible).

Also, mention (or link to) scope here. For example, if I define a variable inside of an if / fi block, does it escape to a higher context? What about using the same variable names and scope?
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