## FilterChains and FilterReaders

Consider the flexibility of Unix pipes. If you wanted, for example, to copy just those lines that contained the string blee from the first 10 lines of a text file 'foo' (you wouldn't want to filter a binary file) to a file 'bar', you would do something like:

`cat foo|head -n10|grep blee > bar`

Apache Ant was not flexible enough. There was no way for the `<copy>` task to do something similar. If you wanted the `<copy>` task to get the first 10 lines, you would have had to create special attributes:

`<copy file="foo" tofile="bar" head="10" contains="blee"/>`

The obvious problem thus surfaced: Ant tasks would not be able to accommodate such data transformation attributes as they would be endless. The task would also not know in which order these attributes were to be interpreted. That is, must the task execute the contains attribute first and then the head attribute or vice-versa? What Ant tasks needed was a mechanism to allow pluggable filter (data transformer) chains. Ant would provide a few filters for which there have been repeated requests. Users with special filtering needs would be able to easily write their own and plug them in.

The solution was to refactor data transformation oriented tasks to support FilterChains. A FilterChain is a group of ordered FilterReaders. Users can define their own FilterReaders by just extending the java.io.FilterReader class. Such custom FilterReaders can be easily plugged in as nested elements of `<filterchain>` by using `<filterreader>` elements.

Example:

>     <copy file="${src.file}" tofile="${dest.file}">
>       <filterchain>
>         <filterreader classname="your.extension.of.java.io.FilterReader">
>           <param name="foo" value="bar"/>
>         </filterreader>
>         <filterreader classname="another.extension.of.java.io.FilterReader">
>           <classpath>
>             <pathelement path="${classpath}"/>
>           </classpath>
>           <param name="blah" value="blee"/>
>           <param type="abra" value="cadabra"/>
>         </filterreader>
>       </filterchain>
>     </copy>

Ant provides some built-in filter readers. These filter readers can also be declared using a syntax similar to the above syntax. However, they can be declared using some simpler syntax also.

Example:

>     <loadfile srcfile="${src.file}" property="src.file.head">
>       <filterchain>
>         <headfilter lines="15"/>
>       </filterchain>
>     </loadfile>

is equivalent to:

>     <loadfile srcfile="${src.file}" property="src.file.head">
>       <filterchain>
>         <filterreader classname="org.apache.tools.ant.filters.HeadFilter">
>           <param name="lines" value="15"/>
>         </filterreader>
>       </filterchain>
>     </loadfile>

The following built-in tasks support nested `<filterchain>` elements.
Concat,
Copy,
LoadFile,
LoadProperties,
LoadResource,
Move
A FilterChain is formed by defining zero or more of the following nested elements.
FilterReader
ClassConstants
EscapeUnicode
ExpandProperties
HeadFilter
LineContains
LineContainsRegExp
PrefixLines
ReplaceTokens
StripJavaComments
StripLineBreaks
StripLineComments
SuffixLines
TabsToSpaces
TailFilter
DeleteCharacters
ConcatFilter
TokenFilter
FixCRLF
SortFilter

### FilterReader

The filterreader element is the generic way to define a filter. User defined filter elements are defined in the build file using this. Please note that built in filter readers can also be defined using this syntax. A FilterReader element must be supplied with a class name as an attribute value. The class resolved by this name must extend java.io.FilterReader. If the custom filter reader needs to be parameterized, it must implement org.apache.tools.type.Parameterizable.

Attribute | Description | Required
classname | The class name of the filter reader. | Yes

#### Nested Elements:

`<filterreader>` supports `<classpath>` and `<param>` as nested elements. Each `<param>` element may take in the following attributes - name, type and value.

The following FilterReaders are supplied with the default distribution.

### ClassConstants

This filters basic constants defined in a Java Class, and outputs them in lines composed of the format name=value. This filter uses the bcel library to understand the Java Class file. See Library Dependencies.

Important: This filter is different from most of the other filters. Most of the filters operate on a sequence of characters. This filter operates on the sequence of bytes that makes up a class. However the bytes arrive to the filter as a sequence of characters. This means that one must be careful on the choice of character encoding to use. Most encoding lose information on conversion from an arbitrary sequence of bytes to characters and back again to bytes. In particular the usual default character encodings (CP152 and UTF-8) do. For this reason, since Ant 1.7, the character encoding ISO-8859-1 is used to convert from characters back to bytes, so one has to use this encoding for reading the java class file.

#### Example:

This loads the basic constants defined in a Java class as Ant properties.

>     <loadproperties srcfile="foo.class" encoding="ISO-8859-1">
>       <filterchain>
>         <classconstants/>
>       </filterchain>
>     </loadproperties>

This loads the constants from a Java class file as Ant properties, prepending the names with a prefix.

>     <loadproperties srcfile="build/classes/org/acme/bar.class"
>                     encoding="ISO-8859-1">
>       <filterchain>
>         <classconstants/>
>         <prefixlines prefix="ini."/>
>       </filterchain>
>     </loadproperties>

### EscapeUnicode

This filter converts its input by changing all non US-ASCII characters into their equivalent unicode escape backslash u plus 4 digits.

since Ant 1.6

#### Example:

This loads the basic constants defined in a Java class as Ant properties.

>     <loadproperties srcfile="non_ascii_property.properties">
>       <filterchain>
>         <filterreader classname="org.apache.tools.ant.filters.EscapeUnicode"/>
>       </filterchain>
>     </loadproperties>

Convenience method:

>     <loadproperties srcfile="non_ascii_property.properties">
>       <filterchain>
>         <escapeunicode/>
>       </filterchain>
>     </loadproperties>

### ExpandProperties

If the data contains data that represents Ant properties (of the form ${...}), that is substituted with the property's actual value.

#### Example:

This results in the property modifiedmessage holding the value "All these moments will be lost in time, like teardrops in the rain"

>     <echo
>       message="All these moments will be lost in time, like teardrops in the ${weather}"
>       file="loadfile1.tmp"
>       />
>     <property name="weather" value="rain"/>
>     <loadfile property="modifiedmessage" srcFile="loadfile1.tmp">
>       <filterchain>
>         <filterreader classname="org.apache.tools.ant.filters.ExpandProperties"/>
>       </filterchain>
>     </loadfile>

Convenience method:

>     <echo
>       message="All these moments will be lost in time, like teardrops in the ${weather}"
>       file="loadfile1.tmp"
>       />
>     <property name="weather" value="rain"/>
>     <loadfile property="modifiedmessage" srcFile="loadfile1.tmp">
>       <filterchain>
>         <expandproperties/>
>       </filterchain>
>     </loadfile>

As of Ant 1.8.3, a nested PropertySet can be specified:

>     <property name="weather" value="rain"/>
>     <loadfile property="modifiedmessage" srcFile="loadfile1.tmp">
>       <filterchain>
>         <expandproperties>
>           <propertyset>
>             <propertyref name="weather" />
>           </propertyset>
>         </expandproperties>
>       </filterchain>
>     </loadfile>

### HeadFilter

This filter reads the first few lines from the data supplied to it.

Parameter Name | Parameter Value | Required
lines | Number of lines to be read. Defaults to "10" A negative value means that all lines are passed (useful with skip) | No
skip | Number of lines to be skipped (from the beginning). Defaults to "0" | No

#### Example:

This stores the first 15 lines of the supplied data in the property src.file.head

>     <loadfile srcfile="${src.file}" property="src.file.head">
>       <filterchain>
>         <filterreader classname="org.apache.tools.ant.filters.HeadFilter">
>           <param name="lines" value="15"/>
>         </filterreader>
>       </filterchain>
>     </loadfile>

Convenience method:

>     <loadfile srcfile="${src.file}" property="src.file.head">
>       <filterchain>
>         <headfilter lines="15"/>
>       </filterchain>
>     </loadfile>

This stores the first 15 lines, skipping the first 2 lines, of the supplied data in the property src.file.head. (Means: lines 3-17)

>     <loadfile srcfile="${src.file}" property="src.file.head">
>       <filterchain>
>         <headfilter lines="15" skip="2"/>
>       </filterchain>
>     </loadfile>

See the testcases for more examples (src\etc\testcases\filters\head-tail.xml in the source distribution).

### LineContains

This filter includes only those lines that contain all the user-specified strings.

Parameter Type | Parameter Value | Required
contains | Substring to be searched for. | Yes
negate | Whether to select non-matching lines only. Since Ant 1.7 | No

#### Example:

This will include only those lines that contain `foo` and `bar`.

>     <filterreader classname="org.apache.tools.ant.filters.LineContains">
>       <param type="contains" value="foo"/>
>       <param type="contains" value="bar"/>
>     </filterreader>

Convenience method:

>     <linecontains>
>       <contains value="foo"/>
>       <contains value="bar"/>
>     </linecontains>

Negation:

>     <filterreader classname="org.apache.tools.ant.filters.LineContains">
>       <param type="negate" value="true"/>
>       <param type="contains" value="foo"/>
>       <param type="contains" value="bar"/>
>     </filterreader>

or

>     <linecontains negate="true">
>       <contains value="foo"/>
>       <contains value="bar"/>
>     </linecontains>

### LineContainsRegExp

Filter which includes only those lines that contain the user-specified regular expression matching strings.

Parameter Type | Parameter Value | Required
regexp | Regular expression to be searched for. | Yes
negate | Whether to select non-matching lines only. Since Ant 1.7 | No
casesensitive | Perform a case sensitive match. Default is true. Since Ant 1.8.2 | No

See Regexp Type for the description of the nested element regexp and of the choice of regular expression implementation.

#### Example:

This will fetch all those lines that contain the pattern `foo`

>     <filterreader classname="org.apache.tools.ant.filters.LineContainsRegExp">
>       <param type="regexp" value="foo*"/>
>     </filterreader>

Convenience method:

>     <linecontainsregexp>
>       <regexp pattern="foo*"/>
>     </linecontainsregexp>

Negation:

>     <filterreader classname="org.apache.tools.ant.filters.LineContainsRegExp">
>       <param type="negate" value="true"/>
>       <param type="regexp" value="foo*"/>
>     </filterreader>

or

>     <linecontainsregexp negate="true">
>       <regexp pattern="foo*"/>
>     </linecontainsregexp>

### PrefixLines

Attaches a prefix to every line.

Parameter Name | Parameter Value | Required
prefix | Prefix to be attached to lines. | Yes

#### Example:

This will attach the prefix `Foo` to all lines.

>     <filterreader classname="org.apache.tools.ant.filters.PrefixLines">
>       <param name="prefix" value="Foo"/>
>     </filterreader>

Convenience method:

>     <prefixlines prefix="Foo"/>

### SuffixLines

Attaches a suffix to every line.

since Ant 1.8.0

Parameter Name | Parameter Value | Required
suffix | Suffix to be attached to lines. | Yes

#### Example:

This will attach the suffix `Foo` to all lines.

>     <filterreader classname="org.apache.tools.ant.filters.SuffixLines">
>       <param name="suffix" value="Foo"/>
>     </filterreader>

Convenience method:

>     <suffixlines suffix="Foo"/>

### ReplaceTokens

This filter reader replaces all strings that are sandwiched between begintoken and endtoken with user defined values.

Parameter Type | Parameter Name | Parameter Value | Required
tokenchar | begintoken | String marking the beginning of a token. Defaults to @ | No
tokenchar | endtoken | String marking the end of a token. Defaults to @ | No
User defined String. | token | User defined search String. | Yes
Not applicable. | propertiesfile | Properties file to take tokens from. | No
Not applicable. | propertiesResource | Properties resource to take tokens from. Note this only works is you use the "convenience" `<replacetokens>` syntax. since Ant 1.8.0 | No
User defined String. | value | Replace-value for the token | No

#### Example:

This replaces occurrences of the string @DATE@ in the data with today's date and stores it in the property ${src.file.replaced}.

>     <tstamp/>
>     <!-- just for explaining the use of the properties -->
>     <property name="src.file" value="orders.csv"/>
>     <property name="src.file.replaced" value="orders.replaced"/>

>     <!-- do the loading and filtering -->
>     <loadfile srcfile="${src.file}" property="${src.file.replaced}">
>       <filterchain>
>         <filterreader classname="org.apache.tools.ant.filters.ReplaceTokens">
>           <param type="token" name="DATE" value="${TODAY}"/>
>         </filterreader>
>       </filterchain>
>     </loadfile>

>     <!-- just for explaining the use of the properties -->
>     <echo message="${orders.replaced}"/>

Convenience method:

>     <tstamp/>
>     <loadfile srcfile="${src.file}" property="${src.file.replaced}">
>       <filterchain>
>         <replacetokens>
>           <token key="DATE" value="${TODAY}"/>
>         </replacetokens>
>       </filterchain>
>     </loadfile>

This replaces occurrences of the string {{DATE}} in the data with today's date and stores it in the property ${src.file.replaced}.

>     <loadfile srcfile="${src.file}" property="${src.file.replaced}">
>       <filterchain>
>         <filterreader classname="org.apache.tools.ant.filters.ReplaceTokens">
>           <param type="tokenchar" name="begintoken" value="{{"/>
>           <param type="tokenchar" name="endtoken" value="}}"/>
>         </filterreader>
>       </filterchain>
>     </loadfile>

Convenience method:

>     <tstamp/>
>     <loadfile srcfile="${src.file}" property="${src.file.replaced}">
>       <filterchain>
>         <replacetokens begintoken="{{" endtoken="}}">
>           <token key="DATE" value="${TODAY}"/>
>         </replacetokens>
>       </filterchain>
>     </loadfile>

This will treat each properties file entry in sample.properties as a token/key pair :

>     <loadfile srcfile="${src.file}" property="${src.file.replaced}">
>       <filterchain>
>         <filterreader classname="org.apache.tools.ant.filters.ReplaceTokens">
>           <param type="propertiesfile" value="sample.properties"/>
>         </filterreader>
>       </filterchain>
>     </loadfile>

This reads the properties from an Ant resource referenced by its id:

>     <string id="embedded-properties">
>     foo=bar
>     baz=xyzzy
>     </string>
>     <loadfile srcfile="${src.file}" property="${src.file.replaced}">
>       <filterchain>
>         <replacetokens propertiesResource="${ant.refid:embedded-properties}"/>
>       </filterchain>
>     </loadfile>

### StripJavaComments

This filter reader strips away comments from the data, using Java syntax guidelines. This filter does not take in any parameters.

#### Example:

>     <loadfile srcfile="${java.src.file}" property="${java.src.file.nocomments}">
>       <filterchain>
>         <filterreader classname="org.apache.tools.ant.filters.StripJavaComments"/>
>       </filterchain>
>     </loadfile>

Convenience method:

>     <loadfile srcfile="${java.src.file}" property="${java.src.file.nocomments}">
>       <filterchain>
>         <stripjavacomments/>
>       </filterchain>
>     </loadfile>

### StripLineBreaks

This filter reader strips away specific characters from the data supplied to it.

Parameter Name | Parameter Value | Required
linebreaks | Characters that are to be stripped out. Defaults to "\r\n" | No

#### Examples:

This strips the '\r' and '\n' characters.

>     <loadfile srcfile="${src.file}" property="${src.file.contents}">
>       <filterchain>
>         <filterreader classname="org.apache.tools.ant.filters.StripLineBreaks"/>
>       </filterchain>
>     </loadfile>

Convenience method:

>     <loadfile srcfile="${src.file}" property="${src.file.contents}">
>       <filterchain>
>         <striplinebreaks/>
>       </filterchain>
>     </loadfile>

This treats the '(' and ')' characters as line break characters and strips them.

>     <loadfile srcfile="${src.file}" property="${src.file.contents}">
>       <filterchain>
>         <filterreader classname="org.apache.tools.ant.filters.StripLineBreaks">
>           <param name="linebreaks" value="()"/>
>         </filterreader>
>       </filterchain>
>     </loadfile>

### StripLineComments

This filter removes all those lines that begin with strings that represent comments as specified by the user.

Parameter Type | Parameter Value | Required
comment | Strings that identify a line as a comment when they appear at the start of the line. | Yes

#### Examples:

This removes all lines that begin with #, --, REM, rem and //

>     <filterreader classname="org.apache.tools.ant.filters.StripLineComments">
>       <param type="comment" value="#"/>
>       <param type="comment" value="--"/>
>       <param type="comment" value="REM "/>
>       <param type="comment" value="rem "/>
>       <param type="comment" value="//"/>
>     </filterreader>

Convenience method:

>     <striplinecomments>
>       <comment value="#"/>
>       <comment value="--"/>
>       <comment value="REM "/>
>       <comment value="rem "/>
>       <comment value="//"/>
>     </striplinecomments>

### TabsToSpaces

This filter replaces tabs with spaces

Parameter Name | Parameter Value | Required
tablength | Defaults to "8" | No

#### Examples:

This replaces tabs in ${src.file} with spaces.

>     <loadfile srcfile="${src.file}" property="${src.file.notab}">
>       <filterchain>
>         <filterreader classname="org.apache.tools.ant.filters.TabsToSpaces"/>
>       </filterchain>
>     </loadfile>

Convenience method:

>     <loadfile srcfile="${src.file}" property="${src.file.notab}">
>       <filterchain>
>         <tabstospaces/>
>       </filterchain>
>     </loadfile>

### TailFilter

This filter reads the last few lines from the data supplied to it.

Parameter Name | Parameter Value | Required
lines | Number of lines to be read. Defaults to "10" A negative value means that all lines are passed (useful with skip) | No
skip | Number of lines to be skipped (from the end). Defaults to "0" | No

#### Background:

With HeadFilter and TailFilter you can extract each part of a text file you want. This graphic shows the dependencies:

Content |  |  |  | Filter
--- | --- | --- | --- | ---
Line 1 |  |  |  |
    <filterchain>
        <headfilter lines="2"/>
    </filterchain>
    <filterchain>
        <tailfilter lines="-1" skip="2"/>
    </filterchain>
    <filterchain>
        <headfilter lines="-1" skip="2"/>
    </filterchain>
    <filterchain>
        <headfilter lines="-1" skip="2"/>
        <tailfilter lines="-1" skip="2"/>
    </filterchain>
    <filterchain>
        <tailfilter lines="2"/>
    </filterchain>
Line 2
Line 3 |
Line 4
Line 5 |
Lines ...
Line 95
Line 96 |
Line 97
Line 98 |
Line 99

#### Examples:

This stores the last 15 lines of the supplied data in the property ${src.file.tail}

>     <loadfile srcfile="${src.file}" property="${src.file.tail}">
>       <filterchain>
>         <filterreader classname="org.apache.tools.ant.filters.TailFilter">
>           <param name="lines" value="15"/>
>         </filterreader>
>       </filterchain>
>     </loadfile>

Convenience method:

>     <loadfile srcfile="${src.file}" property="${src.file.tail}">
>       <filterchain>
>         <tailfilter lines="15"/>
>       </filterchain>
>     </loadfile>

This stores the last 5 lines of the first 15 lines of the supplied data in the property ${src.file.mid}

>     <loadfile srcfile="${src.file}" property="${src.file.mid}">
>       <filterchain>
>         <filterreader classname="org.apache.tools.ant.filters.HeadFilter">
>           <param name="lines" value="15"/>
>         </filterreader>
>         <filterreader classname="org.apache.tools.ant.filters.TailFilter">
>           <param name="lines" value="5"/>
>         </filterreader>
>       </filterchain>
>     </loadfile>

Convenience method:

>     <loadfile srcfile="${src.file}" property="${src.file.mid}">
>       <filterchain>
>         <headfilter lines="15"/>
>         <tailfilter lines="5"/>
>       </filterchain>
>     </loadfile>

This stores the last 10 lines, skipping the last 2 lines, of the supplied data in the property src.file.head. (Means: if supplied data contains 60 lines, lines 49-58 are extracted)

>     <loadfile srcfile="${src.file}" property="src.file.head">
>       <filterchain>
>         <tailfilter lines="10" skip="2"/>
>       </filterchain>
>     </loadfile>

### DeleteCharacters

This filter deletes specified characters.

since Ant 1.6

This filter is only available in the convenience form.

Parameter Name | Parameter Value | Required
chars | The characters to delete. This attribute is backslash enabled. | Yes

#### Examples:

Delete tabs and returns from the data.

>     <deletecharacters chars="\t\r"/>

### ConcatFilter

This filter prepends or appends the content file to the filtered files.

since Ant 1.6

Parameter Name | Parameter Value | Required
prepend | The name of the file which content should be prepended to the file. | No
append | The name of the file which content should be appended to the file. | No

#### Examples:

Do nothing:

>     <filterchain>
>         <concatfilter/>
>     </filterchain>

Adds a license text before each java source:

>     <filterchain>
>         <concatfilter prepend="apache-license-java.txt"/>
>     </filterchain>

### TokenFilter

This filter tokenizes the inputstream into strings and passes these strings to filters of strings. Unlike the other filterreaders, this does not support params, only convenience methods are implemented. The tokenizer and the string filters are defined by nested elements.

since Ant 1.6

Only one tokenizer element may be used, the LineTokenizer is the default if none are specified. A tokenizer splits the input into token strings and trailing delimiter strings.

There may be zero or more string filters. A string filter processes a token and either returns a string or a null. It the string is not null it is passed to the next filter. This proceeds until all the filters are called. If a string is returned after all the filters, the string is outputs with its associated token delimiter (if one is present). The trailing delimiter may be overridden by the delimOutput attribute.

backslash interpretation A number of attributes (including delimOutput) interpret backslash escapes. The following are understood: \n, \r, \f, \t and \\.

Attribute | Description | Required
delimOutput | This overrides the tokendelimiter returned by the tokenizer if it is not empty. This attribute is backslash enabled. | No

The following tokenizers are provided by the default distribution.

LineTokenizer
FileTokenizer
StringTokenizer

The following string filters are provided by the default distribution.

ReplaceString
ContainsString
ReplaceRegex
ContainsRegex
Trim
IgnoreBlank
DeleteCharacters
UniqFilter

The following string filters are provided by the optional distribution.

ScriptFilter

Some of the filters may be used directly within a filter chain. In this case a tokenfilter is created implicitly. An extra attribute "byline" is added to the filter to specify whether to use a linetokenizer (byline="true") or a filetokenizer (byline="false"). The default is "true".

LineTokenizer

This tokenizer splits the input into lines. The tokenizer delimits lines by "\r", "\n" or "\r\n". This is the default tokenizer.

Attribute | Description | Required
includeDelims | Include the line endings in the token. Default is false. | No

#### Examples:

Convert input current line endings to unix style line endings.

>     <tokenfilter delimoutput="\n"/>

Remove blank lines.

>     <tokenfilter>
>         <ignoreblank/>
>     </tokenfilter>

FileTokenizer

This tokenizer treats all the input as a token. So be careful not to use this on very large input.

#### Examples:

Replace the first occurrence of package with //package.

>     <tokenfilter>
>           <filetokenizer/>
>           <replaceregex pattern="([\n\r]+[ \t]*|^[ \t]*)package"
>                         flags="s"
>                         replace="\1//package"/>
>     </tokenfilter>

StringTokenizer

This tokenizer is based on java.util.StringTokenizer. It splits up the input into strings separated by white space, or by a specified list of delimiting characters. If the stream starts with delimiter characters, the first token will be the empty string (unless the delimsaretokens attribute is used).

Attribute | Description | Required
delims | The delimiter characters. White space is used if this is not set. (White space is defined in this case by java.lang.Character.isWhitespace()). | No
delimsaretokens | If this is true, each delimiter character is returned as a token. Default is false. | No
suppressdelims | If this is true, delimiters are not returned. Default is false. | No
includeDelims | Include the delimiters in the token. Default is false. | No

#### Examples:

Surround each non space token with a "[]".

>     <tokenfilter>
>         <stringtokenizer/>
>         <replaceregex pattern="(.+)" replace="[\1]"/>
>     </tokenfilter>

ReplaceString

This is a simple filter to replace strings. This filter may be used directly within a filterchain.

Attribute | Description | Required
from | The string that must be replaced. | Yes
to | The new value for the replaced string. When omitted an empty string is used. | No

#### Examples:

Replace "sun" with "moon".

>     <tokenfilter>
>         <replacestring from="sun" to="moon"/>
>     </tokenfilter>

ContainsString

This is a simple filter to filter tokens that contains a specified string.

Attribute | Description | Required
contains | The string that the token must contain. | Yes

#### Examples:

Include only lines that contain "foo";

>     <tokenfilter>
>         <containsstring contains="foo"/>
>     </tokenfilter>

ReplaceRegex

This string filter replaces regular expressions. This filter may be used directly within a filterchain.

See Regexp Type concerning the choice of the implementation.

Attribute | Description | Required
pattern | The regular expression pattern to match in the token. | Yes
replace | The substitution pattern to replace the matched regular expression. When omitted an empty string is used. | No
flags | See ReplaceRegexp for an explanation of regex flags. | No

#### Examples:

Replace all occurrences of "hello" with "world", ignoring case.

>     <tokenfilter>
>         <replaceregex pattern="hello" replace="world" flags="gi"/>
>     </tokenfilter>

ContainsRegex

This filters strings that match regular expressions. The filter may optionally replace the matched regular expression. This filter may be used directly within a filterchain.

See Regexp Type concerning the choice of regular expression implementation.

Attribute | Description | Required
pattern | The regular expression pattern to match in the token. | Yes
replace | The substitution pattern to replace the matched regular expression. When omitted the original token is returned. | No
flags | See ReplaceRegexp for an explanation of regex flags. | No

#### Examples:

Filter lines that contain "hello" or "world", ignoring case.

>     <tokenfilter>
>         <containsregex pattern="(hello|world)" flags="i"/>
>     </tokenfilter>

This example replaces lines like "SUITE(TestSuite, bits);" with "void register_bits();" and removes other lines.

>     <tokenfilter>
>         <containsregex
>             pattern="^ *SUITE\(.*,\s*(.*)\s*\).*"
>             replace="void register_\1();"/>
>     </tokenfilter>

Trim

This filter trims whitespace from the start and end of tokens. This filter may be used directly within a filterchain.

IgnoreBlank

This filter removes empty tokens. This filter may be used directly within a filterchain.

DeleteCharacters

This filter deletes specified characters from tokens.

Attribute | Description | Required
chars | The characters to delete. This attribute is backslash enabled. | Yes

#### Examples:

Delete tabs from lines, trim the lines and removes empty lines.

>     <tokenfilter>
>         <deletecharacters chars="\t"/>
>         <trim/>
>         <ignoreblank/>
>     </tokenfilter>

UniqFilter

Suppresses all tokens that match their ancestor token. It is most useful if combined with a sort filter.

This filter may be used directly within a filterchain.

#### Example:

This suppresses duplicate lines.

>     <tokenfilter>
>       <uniqfilter/>
>     </tokenfilter>

ScriptFilter

This is an optional filter that executes a script in a Apache BSF or JSR 223 supported language. See the Script task for an explanation of scripts and dependencies.

The script is provided with an object self that has getToken() and setToken(String) methods. The getToken() method returns the current token. The setToken(String) method replaces the current token.

This filter may be used directly within a filterchain.

Attribute | Description | Required
language | The programming language the script is written in. Must be a supported Apache BSF or JSR 223 language | Yes
manager | The script engine manager to use. See the script task for using this attribute. | No - default is "auto"
src | The location of the script as a file, if not inline | No
setbeans | whether to have all properties, references and targets as global variables in the script. since Ant 1.8.0 | No, default is "true".
classpath | The classpath to pass into the script. | No
classpathref | The classpath to use, given as a reference to a path defined elsewhere. | No

This filter can take a nested <classpath> element. See the script task on how to use this element.

#### Examples:

Convert to uppercase:

>     <tokenfilter>
>         <scriptfilter language="javascript">
>             self.setToken(self.getToken().toUpperCase());
>         </scriptfilter>
>     </tokenfilter>

Remove lines containing the string "bad" while copying text files:

>     <copy todir="dist">
>       <fileset dir="src" includes="**/*.txt"/>
>       <filterchain>
>         <scriptfilter language="beanshell">
>             if (self.getToken().indexOf("bad") != -1) {
>                 self.setToken(null);
>             }
>         </scriptfilter>
>       </filterchain>
>     </copy>

#### Custom tokenizers and string filters

Custom string filters and tokenizers may be plugged in by extending the interfaces org.apache.tools.ant.filters.TokenFilter.Filter and org.apache.tools.ant.util.Tokenizer respectly. They are defined the build file using `<typedef/>`. For example a string filter that capitalizes words may be declared as:

>     package my.customant;
>     import org.apache.tools.ant.filters.TokenFilter;

>     public class Capitalize
>         implements TokenFilter.Filter
>     {
>         public String filter(String token) {
>             if (token.length() == 0)
>                 return token;
>             return token.substring(0, 1).toUpperCase() +
>                     token.substring(1);
>        }
>     }

This may be used as follows:

>       <typedef name="capitalize" classname="my.customant.Capitalize"
>                classpath="my.customant.path"/>
>       <copy file="input" tofile="output">
>         <filterchain>
>           <tokenfilter>
>             <stringtokenizer/>
>             <capitalize/>
>           </tokenfilter>
>         </filterchain>
>       </copy>

### SortFilter

since Ant 1.8.0

The sort filter reads all lines and sorts them. The sort order can be reversed and it is possible to specify a custom implementation of the `java.util.Comparator` interface to get even more control.

Parameter Name | Parameter Value | Required
reverse | whether to reverse the sort order, defaults to false. Note: this parameter is ignored if the comparator parameter is present as well. | No
comparator | Class name of a class that implements `java.util.Comparator` for Strings. This class will be used to determine the sort order of lines. | No

This filter is also available using the name `sortfilter`. The `reverse` parameter becomes an attribute, `comparator` can be specified by using a nested element.

#### Examples:

>       <copy todir="build">
>           <fileset dir="input" includes="*.txt"/>
>           <filterchain>
>               <sortfilter/>
>           </filterchain>
>       </copy>

Sort all files `*.txt` from src location into build location. The lines of each file are sorted in ascendant order comparing the lines via the `String.compareTo(Object o)` method.

>       <copy todir="build">
>           <fileset dir="input" includes="*.txt"/>
>           <filterchain>
>               <sortfilter reverse="true"/>
>           </filterchain>
>       </copy>

Sort all files `*.txt` from src location into reverse order and copy them into build location.

>       <copy todir="build">
>           <fileset dir="input" includes="*.txt"/>
>           <filterchain>
>               <filterreader classname="org.apache.tools.ant.filters.SortFilter">
>                 <param name="comparator" value="org.apache.tools.ant.filters.EvenFirstCmp"/>
>               </filterreader>
>           </filterchain>
>       </copy>

Sort all files `*.txt` from src location using as sorting criterium `EvenFirstCmp` class, that sorts the file lines putting even lines first then odd lines for example. The modified files are copied into build location. The `EvenFirstCmp`, has to an instanciable class via `Class.newInstance()`, therefore in case of inner class has to be static. It also has to implement `java.util.Comparator` interface, for example:

            package org.apache.tools.ant.filters;
            ...(omitted)
              public final class EvenFirstCmp implements <b>Comparator</b> {
                public int compare(Object o1, Object o2) {
                ...(omitted)
                }
              }

The example above is equivalent to:

>       <componentdef name="evenfirst"
>                     classname="org.apache.tools.ant.filters.EvenFirstCmp"/>
>       <copy todir="build">
>           <fileset dir="input" includes="*.txt"/>
>           <filterchain>
>               <sortfilter>
>                   <evenfirst/>
>               </sortfilter>
>           </filterchain>
>       </copy>