Apache Ant has lots of useful built-in tasks. However, a task for merging text files is not among them. Fortunately, we can combine some built-in tasks to achieve this goal.

Below, you’ll find the macro along a simple demo:

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<project default="merge-demo">

<target name="merge-demo">
    <merge tofile="merged.txt">
        <sourcefiles>
            <fileset dir="inputfiles"></fileset>
        </sourcefiles>
    </merge>
</target>

    <!-- = = = = = = = = = = = = = = = = =
     macrodef: merge          
    = = = = = = = = = = = = = = = = = -->
    <macrodef name="merge">
        <attribute name="tofile"></attribute>
        <element name="sourcefiles"></element>
       
        <sequential>
            <tempfile property="temp.file" prefix="ant.merge." deleteonexit="true"></tempfile>
           
            <concat destfile="${temp.file}" fixlastline="true">
                <sourcefiles></sourcefiles>
            </concat>
           
            <copy file="${temp.file}" tofile="@{tofile}">
                <filterchain>
                    <tokenfilter>
                        <linetokenizer></linetokenizer>
                    </tokenfilter>
                    <sortfilter></sortfilter>
                    <uniqfilter></uniqfilter>
                </filterchain>
            </copy>
        </sequential>
    </macrodef>
</project>

Remarks and Caveats

  • Contents of all files are sorted by line.
  • Duplicate lines are removed.

Example

The example runs on the following directory:
ant-merge-dirstructure

with the following file contents:

file1.txt

# random prefix	file	line	remark
7609	file1.txt	1
24307	file1.txt	2
31889	file1.txt	3	no newline afterwards

file2.txt

# random prefix	file	line	remark
5808	file2.txt	1
32706	file2.txt	2	preceding empty line

7848	file2.txt	3	following empty line
17727	file2.txt	4
3071	file2.txt	5	one newline afterwards

file3.txt

# random prefix	file	line	remark
16411	file3.txt	1
10605	file3.txt	2	followed by several newlines

Once we run the Ant script, the resulting file will look as follows:
merged.txt


# random prefix	file	line	remark
10605	file3.txt	2	followed by several newlines
16411	file3.txt	1
17727	file2.txt	4
24307	file1.txt	2
3071	file2.txt	5	one newline afterwards
31889	file1.txt	3	no newline afterwards
32706	file2.txt	2	preceding empty line
5808	file2.txt	1
7609	file1.txt	1
7848	file2.txt	3	following empty line