File extension is in extensions list
Given a file name and a list of extensions (including the dot), tell whether the file's extension is in the extensions list. The check should be case insensitive. The file might not have an extension.
Haskell
<lang Haskell> import Data.List import qualified Data.Char as Ch
toLower :: String -> String toLower = map Ch.toLower
isExt :: String -> [String] -> Bool isExt filename extensions = any (`elem` (tails . toLower $ filename)) $ map toLower extensions </lang>
The code defining isExt could be done point free: <lang Haskell> isExt filename = any (`elem` (tails . toLower $ filename)) . map toLower </lang>
Overcoming the one-liner urge on behalf of being more comprehensible would give: <lang Haskell> isExt filename extensions = any (`elem` allTails) lowerExtensions
where allTails = tails . toLower $ filename
lowerExtensions = map toLower extensions </lang>
J
Solution: <lang j>getExt=: }.~ i:&'.' isExt=: e.~&:(tolower&.>) getExt&.>@boxopen</lang> Usage: <lang j> Exts=: <;._1 ' .o .ijs .ij .p'
TestFiles=: <;._1 ' foo.o blab.iJ dram. lat.P win.dll foo' Exts isExt TestFiles
1 1 0 1 0 0</lang>
Java
<lang java5>import java.util.Arrays; import java.util.Comparator;
public class FileExt{ public static void main(String[] args){ String[] tests = {"text.txt", "text.TXT", "test.tar.gz", "test/test2.exe", "test\\test2.exe", "test", "a/b/c\\d/foo"}; String[] exts = {".txt",".gz","",".bat"};
System.out.println("Extensions: " + Arrays.toString(exts) + "\n");
for(String test:tests){ System.out.println(test +": " + extIsIn(test, exts)); } }
public static boolean extIsIn(String test, String... exts){ int lastSlash = Math.max(test.lastIndexOf('/'), test.lastIndexOf('\\')); //whichever one they decide to use today String filename = test.substring(lastSlash + 1);//+1 to get rid of the slash or move to index 0 if there's no slash
//end of the name if no dot, last dot index otherwise int lastDot = filename.lastIndexOf('.') == -1 ? filename.length() : filename.lastIndexOf('.'); String ext = filename.substring(lastDot);//everything at the last dot and after is the extension
Arrays.sort(exts);//sort for the binary search
return Arrays.binarySearch(exts, ext, new Comparator<String>() { //just use the built-in binary search method @Override //it will let us specify a Comparator and it's fast enough public int compare(String o1, String o2) { return o1.compareToIgnoreCase(o2); } }) >= 0;//binarySearch returns negative numbers when it's not found } } </lang>
- Output:
Extensions: [.txt, .gz, , .bat] text.txt: true text.TXT: true test.tar.gz: true test/test2.exe: false test\test2.exe: false test: true a/b/c\d/foo: true
Perl 6
<lang perl6>my @ext = < .c .o >;
for < foo.C foo.zkl foo foo. > {
when / :i @ext $ / { say "$_\t$/ is in the list" } when / '.' <-[.]>* $ / { say "$_\t$/ is not in the list" } default { say "$_\t (has no extension)" }
}</lang>
- Output:
foo.C .C is in the list foo.zkl .zkl is not in the list foo (has no extension) foo. . is not in the list
Python
<lang Python> import os
def isExt(filename, extensions):
return os.path.splitext(filename.lower())[-1] in [e.lower() for e in extensions]
</lang>
REXX
Programming note: extra code was added to:
- display some error/warning messages
- handle the case of the filename having a path
- handle the case of different types of path separators
- handle the case of the filename having no file extension
- handle cases of the filename ending in a period
- handle cases of the filename ending in multiple periods
<lang rexx>/*REXX program displays if a filename has a known extension (per a list)*/ extensions='.bat .cmd .com .dat .dll .exe .ini .jpg .jpeg .log .sys .txt'
/* [↑] above would be some EXTs.*/
parse arg fn /*get the filename from the C.L. */ fn=strip(fn) /*remove any superfluous blanks. */ if fn== then exit /*No fn specified? Then exit.*/ afn=translate(fn,'/',"\") /*handle both versions of pathSep*/ afn=substr(fn,lastpos('/',afn)+1) /*pick off the filename from path*/ p=lastpos('.',afn) /*find the last position of a dot*/ if p==0 | p==length(afn) then do /*no dot or dot is at end of name*/
say 'Filename ' fn " has no extension." exit end
ft=substr(afn,p) /*pickoff the fileType (fileExt).*/ upper ft extensions /*uppercase a couple of REXX vars*/ if wordpos(ft,extensions)==0 then _='an unknown'
else _= 'a known'
say 'Filename ' fn "has" _ 'extension.'</lang>
Ruby
<lang ruby>extensions = [".c",".o",""] ["foo.C","foo.zkl","foo","foo."].each{|f| p extensions.include?( File.extname(f).downcase )} </lang>
- Output:
true false true true
Scala
<lang Scala> def isExt(fileName: String, extensions: List[String]): Boolean = {
extensions.map { _.toLowerCase }.exists { fileName.toLowerCase endsWith _ }
} </lang>
zkl
<lang zkl>var exts=T(".c",".o",""); fcn hasExtension(fname){ exts.holds(File.splitFileName(fname)[3].toLower()) } T("foo.C","foo.zkl","foo","foo.").apply(hasExtension).println();</lang>
- Output:
L(True,False,True,True)