To see the OS-dependent characters used for formatting filenames (here, when running on Windows):
assert File.separator == '\\' && File.separatorChar == '\\' as char
//used for formatting file names
assert File.pathSeparator == ';' && File.pathSeparatorChar == ';' as char
Instances of File are immutable representations of objects in the file system, that may or may not exist. To see different formats of a filename (here, when running within D:\Groovy\Scripts directory):
def f= new File('File.txt') //relative file name
assert f.name == 'File.txt'
assert ! f.isAbsolute()
assert f.path == 'File.txt'
assert f.parent == null
assert f.absolutePath == 'D:\\Groovy\\Scripts\\File.txt' //returns a string
assert f.absoluteFile.toString() == 'D:\\Groovy\\Scripts\\File.txt'
//returns a File object instead of string
assert f.canonicalPath == 'D:\\Groovy\\Scripts\\File.txt'
assert f.canonicalFile.toString() == 'D:\\Groovy\\Scripts\\File.txt'
//returns a File object instead of string
assert f.toURI().toString() == 'file:/D:/Groovy/Scripts/File.txt'
//toURI() returns a URI object
f= new File('D:/Groovy/Scripts/File.txt') //absolute file name
assert f.name == 'File.txt'
assert f.isAbsolute()
assert f.path == 'D:\\Groovy\\Scripts\\File.txt'
assert f.parent == 'D:\\Groovy\\Scripts'
assert f.parentFile.toString() == 'D:\\Groovy\\Scripts'
//returns a File object instead of string
assert f.absolutePath == 'D:\\Groovy\\Scripts\\File.txt'
assert f.canonicalPath == 'D:\\Groovy\\Scripts\\File.txt'
f= new File('../File.txt')
assert f.name == 'File.txt'
assert ! f.isAbsolute()
assert f.path == '..\\File.txt'
assert f.parent == '..'
assert f.absolutePath == 'D:\\Groovy\\Scripts\\..\\File.txt'
assert f.canonicalPath == 'D:\\Groovy\\File.txt'
f= new File('') //current directory
assert f.name == ''
assert ! f.isAbsolute()
assert f.path == ''
assert f.parent == null
assert f.absolutePath == 'D:\\Groovy\\Scripts'
assert f.canonicalPath == 'D:\\Groovy\\Scripts'
assert new File('File.txt') == new File('File.txt')
//compares two filenames' lexical names
assert new File('File.txt').compareTo(new File('File.txt')) == 0
//equivalent method name
assert new File('File.txt') != new File('../Scripts/File.txt')
//lexical names different (although files are the same)
None of the above example's files were created. Files are only created by some event:
def f1= new File('File1.txt')
f1 << 'abcdefg'
//file created by writing to it; file appended to if it already exists
assert f1.length() == 7 && f1.size() == 7
assert f1.isFile() && ! f1.isDirectory() && ! f1.isHidden()
def f2= new File('D:/Groovy/Scripts', 'File2.txt')
//we can optionally supply the parent, either as a string...
f2= new File(new File('D:/Groovy/Scripts'), 'File2.txt')
//...or as a File object
assert ! f2.exists()
f2.createNewFile() //if it doesn't already exist
assert f2.exists()
def d1= new File('Directory1')
d1.mkdir() //make directory, if it doesn't already exist
def d2= new File('Directory2/SubDir1')
d2.mkdirs()
//make directory, including necessary but nonexistent parent directories
println f1.getFreeSpace()
//the number of unallocated bytes in the partition this abstract file is in
println f1.getUsableSpace()
//the number of bytes available to this virtual machine in the partition
//this abstract file is in
println f1.getTotalSpace() //the size of the partition this abstract file is in
//We can set file permissions:
assert f2.setWritable(true, false) && f2.canWrite()
//set writable permission for every user
assert f2.setWritable(true) && f2.canWrite()
//set writable permission on file for owner only
assert f2.setWritable(false, false) && ! f2.canWrite()
//unset writable permission for every user
assert f2.setWritable(false) && ! f2.canWrite()
//unset writable permission on file for owner only
f2.writable= true //property format for owner only
assert f2.canWrite()
assert f2.setReadOnly() && ! f2.canWrite()
assert f2.setExecutable(true, false) && f2.canExecute()
//set executable permission for every user
assert f2.setExecutable(true) && f2.canExecute()
//set executable permission on file for owner only
f2.executable= true //property format for owner only
assert f2.canExecute()
assert ! f2.setExecutable(false)
//returns false because command unsuccessful: can't make file
//nonexecutable on Windows, though can on other systems
assert f2.setReadable(true, false) && f2.canRead()
//set readable permission for every user
assert f2.setReadable(true) && f2.canRead()
//set readable permission on file for owner only
f2.readable= true //property format for owner only
assert f2.canRead()
assert ! f2.setReadable(false)
//can't make file nonreadable on Windows
//We can retrieve a list of files from a directory:
assert new File('D:/Groovy/Scripts').list().toList() ==
['Script.bat', 'File1.txt', 'File2.txt', 'Directory1', 'Directory2']
//list() returns an array of strings
assert new File('Directory2').list().toList() == ['SubDir1']
assert new File('').list() == null
//list() returns null if directory not explicitly specified
assert new File('D:/Groovy/Scripts').list(
[accept:{d, f-> f ==~ /.*?1.*/ }] as FilenameFilter
).toList() == ['File1.txt', 'Directory1']
//filter taking dir (File) and file (String) arguments, returns boolean
assert new File('D:/Groovy/Scripts').list(
{d, f-> f ==~ /.*?1.*/ } as FilenameFilter
).toList() == ['File1.txt', 'Directory1'] //shorter syntax
assert new File('D:/Groovy/Scripts').listFiles().toList()*.name ==
['Script.bat', 'File1.txt', 'File2.txt', 'Directory1', 'Directory2']
//listFiles() returns array of File objects
assert new File('Directory2').listFiles().toList()*.toString() ==
['Directory2\\SubDir1']
assert new File('D:/Groovy/Scripts').listFiles(
{dir, file-> file ==~ /.*?\.txt/ } as FilenameFilter
).toList()*.name == [ 'File1.txt', 'File2.txt' ]
assert new File('D:/Groovy/Scripts').listFiles(
[accept:{file-> file ==~ /.*?\.txt/ }] as FileFilter
).toList()*.name == [ 'File1.txt', 'File2.txt' ]
//use a filter taking one argument only, returning boolean
//Renaming and deleting files:
f2.renameTo( new File('RenamedFile2.txt') )
assert f2.name == 'File2.txt' //because File object is immutable
assert new File('RenamedFile2.txt').exists()
[new File('RenamedFile2.txt'), new File('Directory1'), new File('Directory2')].
each{ it.delete() } //delete files
assert ! new File('RenamedFile2.txt').exists()
assert ! new File('Directory1').exists()
assert new File('Directory2').exists()
//because each sub-directory must be deleted separately
assert new File('Directory2/SubDir1').delete() //returns true if file deleted OK
assert new File('Directory2').delete()
assert ! new File('Directory2').exists()
new File('File1.txt').deleteOnExit()
assert new File('File1.txt').exists() //but will be deleted when VM exits
def mod= new File('File1.txt').lastModified()
assert new File('File1.txt').setLastModified(mod - 60000)
//60 seconds previously, returns true if successful
new File('File1.txt').lastModified= mod - 120000
//property syntax for setting only
assert new File('File1.txt').lastModified() == mod - 120000
To perform general file manipulation in a file system, we can retrieve all the topmost directories:
println File.listRoots().toList()*.toString()
//listRoots() returns an array of File objects
To create a temporary file, with given prefix (of at least 3 chars) and suffix:
File.createTempFile('Tem', '.txt')
//created in directory for temporary files
File.createTempFile('Tem', '.txt', new File('D:\\Groovy\\Scripts'))
//eg, created D:/Groovy/Scripts/Tem59217.txt
We can read and write to files in various ways, as in this example:
def f1= new File('File1.txt') << 'abcdefg:hijklmnop:qrstuv:wxyz\n'
//create and write to the file
f1.leftShift('123:456:7890\n') //equivalent method name
new File('File2.txt').createNewFile()
[new File('Directory1'), new File('Directory2/SubDir1')].each{ it.mkdirs() }
def list= []
new File('D:\\Groovy\\Scripts').eachFile{ list<< it.name }
//eachFile() returns a list of File objects
assert list ==
['Script.bat', 'File1.txt', 'File2.txt', 'Directory1', 'Directory2']
list= []
new File('D:\\Groovy\\Scripts').eachFileMatch(~/File.*?\.txt/){ list<< it.name }
//a regular expression, or any caseable expression
assert list == ['File1.txt', 'File2.txt']
list= []
new File('D:\\Groovy\\Scripts').eachFileRecurse{ list<< it.name }
assert list == ['Script.bat', 'File1.txt', 'File2.txt',
'Directory1', 'Directory2', 'SubDir1']
list= []
new File('D:\\Groovy\\Scripts').eachDir{ list<< it.name }
assert list == ['Directory1', 'Directory2']
list= []
f1.eachLine{ list<< it }
assert list == [ 'abcdefg:hijklmnop:qrstuv:wxyz', '123:456:7890' ]
list= f1.readLines()
assert list == [ 'abcdefg:hijklmnop:qrstuv:wxyz', '123:456:7890' ]
list= []
f1.splitEachLine(':'){ list<< it } //splits each line into a list
assert list == [
['abcdefg', 'hijklmnop', 'qrstuv', 'wxyz'],
['123', '456', '7890'],
]
def f2= new File('File2.txt')
f2.write('abcdefg\n') //can only write strings
assert f2.getText() == 'abcdefg\n'
f2.append('hijklmnop,')
f2.append(42) //can append any object
assert f2.getText() == '''abcdefg
hijklmnop,42'''
f2.write('???????????????', 'unicode') //overwrites existing contents
assert f2.getText('unicode') == '???????????????'
f2.append('???????????????', 'unicode') //also appends unicode marker 0xFEFF
assert f2.getText('unicode') == '???????????????' + (0xFEFF as char) + '???????????????'
[ new File('File1.txt'),
new File('File2.txt'),
new File('Directory1'),
new File('Directory2/SubDir1'),
new File('Directory2'),
].each{ it.delete() } //delete files used by this example
from：http://groovy.codehaus.org/JN2015-Files