How do I concatenate multiple files in Gradle? - gradle

Question

Is there an easy way to concatenate multiple text files into a single one in Gradle? The build script should look something like this:
FileCollection jsDeps = files(
'file1.js',
'file2.js'
// other files here
)
task concatenate << {
// concatenate the files to file.js
}
I am using Gradle 2.3.

Answer 1

leftShift / "<<" is deprecated in gradle 3.4 You may use something like:
task concatenate {
doLast {
def toConcatenate = files("filename1", "filename2", ...)
def outputFileName = "output.txt"
def output = new File(outputFileName)
output.write('') // truncate output if needed
toConcatenate.each { f -> output << f.text }
}

Answer 2

You can also register the files as inputs/outputs to help with incremental builds. It's especially helpful with larger files.
something like this:
task 'concatenateFiles', {
inputs.files( fileTree( "path/to/dir/with/files" ) ).skipWhenEmpty()
outputs.file( "$project.buildDir/tmp/concatinated.js" )
doLast {
outputs.files.singleFile.withOutputStream { out ->
for ( file in inputs.files ) file.withInputStream { out << it << '\n' }
}
}
}
Instead of the fileTree, it can also be replaced with sourceset/sourceset output, specific files, outputs from a different task, etc.
Gradle doc on task inputs/output
Concatenating files in groovy

Answer 3

The following task should do the job:
task concatenate << {
def toConcatenate = files('f1', 'f2', 'f3')
def output = new File('output')
toConcatenate.each { f -> output << f.text }
}

Answer 4

(new File('test.js')).text = file('test1.js').getText() + file('test2.js').getText()
UPDATE:
For collections.
(new File('test.js')).text = files('test1.js', 'test2.js').collect{it.getText()}.join("\n")