Perl
@ls = `ls *.txt`; chomp @ls; foreach$file(@ls){ $file_utf8 = $file; $file_utf8 =~ s/\.(.*)?$//; $file_utf8.= ".utf8"; system("nkf -w $file > tmp"); system("mv tmp $file_utf8"); print "nkf -w $file > tmp\n"; }