| [ Index ] |
PHP Cross Reference of Unnamed Project |
[Summary view] [Print] [Text view]
1 =head1 NAME 2 3 perlfaq5 - Files and Formats ($Revision: 10126 $) 4 5 =head1 DESCRIPTION 6 7 This section deals with I/O and the "f" issues: filehandles, flushing, 8 formats, and footers. 9 10 =head2 How do I flush/unbuffer an output filehandle? Why must I do this? 11 X<flush> X<buffer> X<unbuffer> X<autoflush> 12 13 Perl does not support truly unbuffered output (except insofar as you 14 can C<syswrite(OUT, $char, 1)>), although it does support is "command 15 buffering", in which a physical write is performed after every output 16 command. 17 18 The C standard I/O library (stdio) normally buffers characters sent to 19 devices so that there isn't a system call for each byte. In most stdio 20 implementations, the type of output buffering and the size of the 21 buffer varies according to the type of device. Perl's C<print()> and 22 C<write()> functions normally buffer output, while C<syswrite()> 23 bypasses buffering all together. 24 25 If you want your output to be sent immediately when you execute 26 C<print()> or C<write()> (for instance, for some network protocols), 27 you must set the handle's autoflush flag. This flag is the Perl 28 variable C<$|> and when it is set to a true value, Perl will flush the 29 handle's buffer after each C<print()> or C<write()>. Setting C<$|> 30 affects buffering only for the currently selected default filehandle. 31 You choose this handle with the one argument C<select()> call (see 32 L<perlvar/$E<verbar>> and L<perlfunc/select>). 33 34 Use C<select()> to choose the desired handle, then set its 35 per-filehandle variables. 36 37 $old_fh = select(OUTPUT_HANDLE); 38 $| = 1; 39 select($old_fh); 40 41 Some modules offer object-oriented access to handles and their 42 variables, although they may be overkill if this is the only thing you 43 do with them. You can use C<IO::Handle>: 44 45 use IO::Handle; 46 open my( $printer ), ">", "/dev/printer"); # but is this? 47 $printer->autoflush(1); 48 49 or C<IO::Socket> (which inherits from C<IO::Handle>): 50 51 use IO::Socket; # this one is kinda a pipe? 52 my $sock = IO::Socket::INET->new( 'www.example.com:80' ); 53 54 $sock->autoflush(); 55 56 You can also flush an C<IO::Handle> object without setting 57 C<autoflush>. Call the C<flush> method to flush the buffer yourself: 58 59 use IO::Handle; 60 open my( $printer ), ">", "/dev/printer"); 61 $printer->flush; # one time flush 62 63 64 =head2 How do I change, delete, or insert a line in a file, or append to the beginning of a file? 65 X<file, editing> 66 67 (contributed by brian d foy) 68 69 The basic idea of inserting, changing, or deleting a line from a text 70 file involves reading and printing the file to the point you want to 71 make the change, making the change, then reading and printing the rest 72 of the file. Perl doesn't provide random access to lines (especially 73 since the record input separator, C<$/>, is mutable), although modules 74 such as C<Tie::File> can fake it. 75 76 A Perl program to do these tasks takes the basic form of opening a 77 file, printing its lines, then closing the file: 78 79 open my $in, '<', $file or die "Can't read old file: $!"; 80 open my $out, '>', "$file.new" or die "Can't write new file: $!"; 81 82 while( <$in> ) 83 { 84 print $out $_; 85 } 86 87 close $out; 88 89 Within that basic form, add the parts that you need to insert, change, 90 or delete lines. 91 92 To prepend lines to the beginning, print those lines before you enter 93 the loop that prints the existing lines. 94 95 open my $in, '<', $file or die "Can't read old file: $!"; 96 open my $out, '>', "$file.new" or die "Can't write new file: $!"; 97 98 print "# Add this line to the top\n"; # <--- HERE'S THE MAGIC 99 100 while( <$in> ) 101 { 102 print $out $_; 103 } 104 105 close $out; 106 107 To change existing lines, insert the code to modify the lines inside 108 the C<while> loop. In this case, the code finds all lowercased 109 versions of "perl" and uppercases them. The happens for every line, so 110 be sure that you're supposed to do that on every line! 111 112 open my $in, '<', $file or die "Can't read old file: $!"; 113 open my $out, '>', "$file.new" or die "Can't write new file: $!"; 114 115 print "# Add this line to the top\n"; 116 117 while( <$in> ) 118 { 119 s/\b(perl)\b/Perl/g; 120 print $out $_; 121 } 122 123 close $out; 124 125 To change only a particular line, the input line number, C<$.>, is 126 useful. First read and print the lines up to the one you want to 127 change. Next, read the single line you want to change, change it, and 128 print it. After that, read the rest of the lines and print those: 129 130 while( <$in> ) # print the lines before the change 131 { 132 print $out $_; 133 last if $. == 4; # line number before change 134 } 135 136 my $line = <$in>; 137 $line =~ s/\b(perl)\b/Perl/g; 138 print $out $line; 139 140 while( <$in> ) # print the rest of the lines 141 { 142 print $out $_; 143 } 144 145 To skip lines, use the looping controls. The C<next> in this example 146 skips comment lines, and the C<last> stops all processing once it 147 encounters either C<__END__> or C<__DATA__>. 148 149 while( <$in> ) 150 { 151 next if /^\s+#/; # skip comment lines 152 last if /^__(END|DATA)__$/; # stop at end of code marker 153 print $out $_; 154 } 155 156 Do the same sort of thing to delete a particular line by using C<next> 157 to skip the lines you don't want to show up in the output. This 158 example skips every fifth line: 159 160 while( <$in> ) 161 { 162 next unless $. % 5; 163 print $out $_; 164 } 165 166 If, for some odd reason, you really want to see the whole file at once 167 rather than processing line by line, you can slurp it in (as long as 168 you can fit the whole thing in memory!): 169 170 open my $in, '<', $file or die "Can't read old file: $!" 171 open my $out, '>', "$file.new" or die "Can't write new file: $!"; 172 173 my @lines = do { local $/; <$in> }; # slurp! 174 175 # do your magic here 176 177 print $out @lines; 178 179 Modules such as C<File::Slurp> and C<Tie::File> can help with that 180 too. If you can, however, avoid reading the entire file at once. Perl 181 won't give that memory back to the operating system until the process 182 finishes. 183 184 You can also use Perl one-liners to modify a file in-place. The 185 following changes all 'Fred' to 'Barney' in F<inFile.txt>, overwriting 186 the file with the new contents. With the C<-p> switch, Perl wraps a 187 C<while> loop around the code you specify with C<-e>, and C<-i> turns 188 on in-place editing. The current line is in C<$_>. With C<-p>, Perl 189 automatically prints the value of C<$_> at the end of the loop. See 190 L<perlrun> for more details. 191 192 perl -pi -e 's/Fred/Barney/' inFile.txt 193 194 To make a backup of C<inFile.txt>, give C<-i> a file extension to add: 195 196 perl -pi.bak -e 's/Fred/Barney/' inFile.txt 197 198 To change only the fifth line, you can add a test checking C<$.>, the 199 input line number, then only perform the operation when the test 200 passes: 201 202 perl -pi -e 's/Fred/Barney/ if $. == 5' inFile.txt 203 204 To add lines before a certain line, you can add a line (or lines!) 205 before Perl prints C<$_>: 206 207 perl -pi -e 'print "Put before third line\n" if $. == 3' inFile.txt 208 209 You can even add a line to the beginning of a file, since the current 210 line prints at the end of the loop: 211 212 perl -pi -e 'print "Put before first line\n" if $. == 1' inFile.txt 213 214 To insert a line after one already in the file, use the C<-n> switch. 215 It's just like C<-p> except that it doesn't print C<$_> at the end of 216 the loop, so you have to do that yourself. In this case, print C<$_> 217 first, then print the line that you want to add. 218 219 perl -ni -e 'print; print "Put after fifth line\n" if $. == 5' inFile.txt 220 221 To delete lines, only print the ones that you want. 222 223 perl -ni -e 'print unless /d/' inFile.txt 224 225 ... or ... 226 227 perl -pi -e 'next unless /d/' inFile.txt 228 229 =head2 How do I count the number of lines in a file? 230 X<file, counting lines> X<lines> X<line> 231 232 One fairly efficient way is to count newlines in the file. The 233 following program uses a feature of tr///, as documented in L<perlop>. 234 If your text file doesn't end with a newline, then it's not really a 235 proper text file, so this may report one fewer line than you expect. 236 237 $lines = 0; 238 open(FILE, $filename) or die "Can't open `$filename': $!"; 239 while (sysread FILE, $buffer, 4096) { 240 $lines += ($buffer =~ tr/\n//); 241 } 242 close FILE; 243 244 This assumes no funny games with newline translations. 245 246 =head2 How can I use Perl's C<-i> option from within a program? 247 X<-i> X<in-place> 248 249 C<-i> sets the value of Perl's C<$^I> variable, which in turn affects 250 the behavior of C<< <> >>; see L<perlrun> for more details. By 251 modifying the appropriate variables directly, you can get the same 252 behavior within a larger program. For example: 253 254 # ... 255 { 256 local($^I, @ARGV) = ('.orig', glob("*.c")); 257 while (<>) { 258 if ($. == 1) { 259 print "This line should appear at the top of each file\n"; 260 } 261 s/\b(p)earl\b/$1}erl/i; # Correct typos, preserving case 262 print; 263 close ARGV if eof; # Reset $. 264 } 265 } 266 # $^I and @ARGV return to their old values here 267 268 This block modifies all the C<.c> files in the current directory, 269 leaving a backup of the original data from each file in a new 270 C<.c.orig> file. 271 272 =head2 How can I copy a file? 273 X<copy> X<file, copy> 274 275 (contributed by brian d foy) 276 277 Use the File::Copy module. It comes with Perl and can do a 278 true copy across file systems, and it does its magic in 279 a portable fashion. 280 281 use File::Copy; 282 283 copy( $original, $new_copy ) or die "Copy failed: $!"; 284 285 If you can't use File::Copy, you'll have to do the work yourself: 286 open the original file, open the destination file, then print 287 to the destination file as you read the original. 288 289 =head2 How do I make a temporary file name? 290 X<file, temporary> 291 292 If you don't need to know the name of the file, you can use C<open()> 293 with C<undef> in place of the file name. The C<open()> function 294 creates an anonymous temporary file. 295 296 open my $tmp, '+>', undef or die $!; 297 298 Otherwise, you can use the File::Temp module. 299 300 use File::Temp qw/ tempfile tempdir /; 301 302 $dir = tempdir( CLEANUP => 1 ); 303 ($fh, $filename) = tempfile( DIR => $dir ); 304 305 # or if you don't need to know the filename 306 307 $fh = tempfile( DIR => $dir ); 308 309 The File::Temp has been a standard module since Perl 5.6.1. If you 310 don't have a modern enough Perl installed, use the C<new_tmpfile> 311 class method from the IO::File module to get a filehandle opened for 312 reading and writing. Use it if you don't need to know the file's name: 313 314 use IO::File; 315 $fh = IO::File->new_tmpfile() 316 or die "Unable to make new temporary file: $!"; 317 318 If you're committed to creating a temporary file by hand, use the 319 process ID and/or the current time-value. If you need to have many 320 temporary files in one process, use a counter: 321 322 BEGIN { 323 use Fcntl; 324 my $temp_dir = -d '/tmp' ? '/tmp' : $ENV{TMPDIR} || $ENV{TEMP}; 325 my $base_name = sprintf "%s/%d-%d-0000", $temp_dir, $$, time; 326 327 sub temp_file { 328 local *FH; 329 my $count = 0; 330 until( defined(fileno(FH)) || $count++ > 100 ) { 331 $base_name =~ s/-(\d+)$/"-" . (1 + $1)/e; 332 # O_EXCL is required for security reasons. 333 sysopen FH, $base_name, O_WRONLY|O_EXCL|O_CREAT; 334 } 335 336 if( defined fileno(FH) ) { 337 return (*FH, $base_name); 338 } 339 else { 340 return (); 341 } 342 } 343 344 } 345 346 =head2 How can I manipulate fixed-record-length files? 347 X<fixed-length> X<file, fixed-length records> 348 349 The most efficient way is using L<pack()|perlfunc/"pack"> and 350 L<unpack()|perlfunc/"unpack">. This is faster than using 351 L<substr()|perlfunc/"substr"> when taking many, many strings. It is 352 slower for just a few. 353 354 Here is a sample chunk of code to break up and put back together again 355 some fixed-format input lines, in this case from the output of a normal, 356 Berkeley-style ps: 357 358 # sample input line: 359 # 15158 p5 T 0:00 perl /home/tchrist/scripts/now-what 360 my $PS_T = 'A6 A4 A7 A5 A*'; 361 open my $ps, '-|', 'ps'; 362 print scalar <$ps>; 363 my @fields = qw( pid tt stat time command ); 364 while (<$ps>) { 365 my %process; 366 @process{@fields} = unpack($PS_T, $_); 367 for my $field ( @fields ) { 368 print "$field: <$process{$field}>\n"; 369 } 370 print 'line=', pack($PS_T, @process{@fields} ), "\n"; 371 } 372 373 We've used a hash slice in order to easily handle the fields of each row. 374 Storing the keys in an array means it's easy to operate on them as a 375 group or loop over them with for. It also avoids polluting the program 376 with global variables and using symbolic references. 377 378 =head2 How can I make a filehandle local to a subroutine? How do I pass filehandles between subroutines? How do I make an array of filehandles? 379 X<filehandle, local> X<filehandle, passing> X<filehandle, reference> 380 381 As of perl5.6, open() autovivifies file and directory handles 382 as references if you pass it an uninitialized scalar variable. 383 You can then pass these references just like any other scalar, 384 and use them in the place of named handles. 385 386 open my $fh, $file_name; 387 388 open local $fh, $file_name; 389 390 print $fh "Hello World!\n"; 391 392 process_file( $fh ); 393 394 If you like, you can store these filehandles in an array or a hash. 395 If you access them directly, they aren't simple scalars and you 396 need to give C<print> a little help by placing the filehandle 397 reference in braces. Perl can only figure it out on its own when 398 the filehandle reference is a simple scalar. 399 400 my @fhs = ( $fh1, $fh2, $fh3 ); 401 402 for( $i = 0; $i <= $#fhs; $i++ ) { 403 print {$fhs[$i]} "just another Perl answer, \n"; 404 } 405 406 Before perl5.6, you had to deal with various typeglob idioms 407 which you may see in older code. 408 409 open FILE, "> $filename"; 410 process_typeglob( *FILE ); 411 process_reference( \*FILE ); 412 413 sub process_typeglob { local *FH = shift; print FH "Typeglob!" } 414 sub process_reference { local $fh = shift; print $fh "Reference!" } 415 416 If you want to create many anonymous handles, you should 417 check out the Symbol or IO::Handle modules. 418 419 =head2 How can I use a filehandle indirectly? 420 X<filehandle, indirect> 421 422 An indirect filehandle is using something other than a symbol 423 in a place that a filehandle is expected. Here are ways 424 to get indirect filehandles: 425 426 $fh = SOME_FH; # bareword is strict-subs hostile 427 $fh = "SOME_FH"; # strict-refs hostile; same package only 428 $fh = *SOME_FH; # typeglob 429 $fh = \*SOME_FH; # ref to typeglob (bless-able) 430 $fh = *SOME_FH{IO}; # blessed IO::Handle from *SOME_FH typeglob 431 432 Or, you can use the C<new> method from one of the IO::* modules to 433 create an anonymous filehandle, store that in a scalar variable, 434 and use it as though it were a normal filehandle. 435 436 use IO::Handle; # 5.004 or higher 437 $fh = IO::Handle->new(); 438 439 Then use any of those as you would a normal filehandle. Anywhere that 440 Perl is expecting a filehandle, an indirect filehandle may be used 441 instead. An indirect filehandle is just a scalar variable that contains 442 a filehandle. Functions like C<print>, C<open>, C<seek>, or 443 the C<< <FH> >> diamond operator will accept either a named filehandle 444 or a scalar variable containing one: 445 446 ($ifh, $ofh, $efh) = (*STDIN, *STDOUT, *STDERR); 447 print $ofh "Type it: "; 448 $got = <$ifh> 449 print $efh "What was that: $got"; 450 451 If you're passing a filehandle to a function, you can write 452 the function in two ways: 453 454 sub accept_fh { 455 my $fh = shift; 456 print $fh "Sending to indirect filehandle\n"; 457 } 458 459 Or it can localize a typeglob and use the filehandle directly: 460 461 sub accept_fh { 462 local *FH = shift; 463 print FH "Sending to localized filehandle\n"; 464 } 465 466 Both styles work with either objects or typeglobs of real filehandles. 467 (They might also work with strings under some circumstances, but this 468 is risky.) 469 470 accept_fh(*STDOUT); 471 accept_fh($handle); 472 473 In the examples above, we assigned the filehandle to a scalar variable 474 before using it. That is because only simple scalar variables, not 475 expressions or subscripts of hashes or arrays, can be used with 476 built-ins like C<print>, C<printf>, or the diamond operator. Using 477 something other than a simple scalar variable as a filehandle is 478 illegal and won't even compile: 479 480 @fd = (*STDIN, *STDOUT, *STDERR); 481 print $fd[1] "Type it: "; # WRONG 482 $got = <$fd[0]> # WRONG 483 print $fd[2] "What was that: $got"; # WRONG 484 485 With C<print> and C<printf>, you get around this by using a block and 486 an expression where you would place the filehandle: 487 488 print { $fd[1] } "funny stuff\n"; 489 printf { $fd[1] } "Pity the poor %x.\n", 3_735_928_559; 490 # Pity the poor deadbeef. 491 492 That block is a proper block like any other, so you can put more 493 complicated code there. This sends the message out to one of two places: 494 495 $ok = -x "/bin/cat"; 496 print { $ok ? $fd[1] : $fd[2] } "cat stat $ok\n"; 497 print { $fd[ 1+ ($ok || 0) ] } "cat stat $ok\n"; 498 499 This approach of treating C<print> and C<printf> like object methods 500 calls doesn't work for the diamond operator. That's because it's a 501 real operator, not just a function with a comma-less argument. Assuming 502 you've been storing typeglobs in your structure as we did above, you 503 can use the built-in function named C<readline> to read a record just 504 as C<< <> >> does. Given the initialization shown above for @fd, this 505 would work, but only because readline() requires a typeglob. It doesn't 506 work with objects or strings, which might be a bug we haven't fixed yet. 507 508 $got = readline($fd[0]); 509 510 Let it be noted that the flakiness of indirect filehandles is not 511 related to whether they're strings, typeglobs, objects, or anything else. 512 It's the syntax of the fundamental operators. Playing the object 513 game doesn't help you at all here. 514 515 =head2 How can I set up a footer format to be used with write()? 516 X<footer> 517 518 There's no builtin way to do this, but L<perlform> has a couple of 519 techniques to make it possible for the intrepid hacker. 520 521 =head2 How can I write() into a string? 522 X<write, into a string> 523 524 See L<perlform/"Accessing Formatting Internals"> for an C<swrite()> function. 525 526 =head2 How can I open a filehandle to a string? 527 X<string>, X<open>, X<IO::Scalar>, X<filehandle> 528 529 (contributed by Peter J. Holzer, hjp-usenet2@hjp.at) 530 531 Since Perl 5.8.0, you can pass a reference to a scalar instead of the 532 filename to create a file handle which you can used to read from or write to 533 a string: 534 535 open(my $fh, '>', \$string) or die "Could not open string for writing"; 536 print $fh "foo\n"; 537 print $fh "bar\n"; # $string now contains "foo\nbar\n" 538 539 open(my $fh, '<', \$string) or die "Could not open string for reading"; 540 my $x = <$fh>; # $x now contains "foo\n" 541 542 With older versions of Perl, the C<IO::String> module provides similar 543 functionality. 544 545 =head2 How can I output my numbers with commas added? 546 X<number, commify> 547 548 (contributed by brian d foy and Benjamin Goldberg) 549 550 You can use L<Number::Format> to separate places in a number. 551 It handles locale information for those of you who want to insert 552 full stops instead (or anything else that they want to use, 553 really). 554 555 This subroutine will add commas to your number: 556 557 sub commify { 558 local $_ = shift; 559 1 while s/^([-+]?\d+)(\d{3})/$1,$2/; 560 return $_; 561 } 562 563 This regex from Benjamin Goldberg will add commas to numbers: 564 565 s/(^[-+]?\d+?(?=(?>(?:\d{3})+)(?!\d))|\G\d{3}(?=\d))/$1,/g; 566 567 It is easier to see with comments: 568 569 s/( 570 ^[-+]? # beginning of number. 571 \d+? # first digits before first comma 572 (?= # followed by, (but not included in the match) : 573 (?>(?:\d{3})+) # some positive multiple of three digits. 574 (?!\d) # an *exact* multiple, not x * 3 + 1 or whatever. 575 ) 576 | # or: 577 \G\d{3} # after the last group, get three digits 578 (?=\d) # but they have to have more digits after them. 579 )/$1,/xg; 580 581 =head2 How can I translate tildes (~) in a filename? 582 X<tilde> X<tilde expansion> 583 584 Use the <> (glob()) operator, documented in L<perlfunc>. Older 585 versions of Perl require that you have a shell installed that groks 586 tildes. Recent perl versions have this feature built in. The 587 File::KGlob module (available from CPAN) gives more portable glob 588 functionality. 589 590 Within Perl, you may use this directly: 591 592 $filename =~ s{ 593 ^ ~ # find a leading tilde 594 ( # save this in $1 595 [^/] # a non-slash character 596 * # repeated 0 or more times (0 means me) 597 ) 598 }{ 599 $1 600 ? (getpwnam($1))[7] 601 : ( $ENV{HOME} || $ENV{LOGDIR} ) 602 }ex; 603 604 =head2 How come when I open a file read-write it wipes it out? 605 X<clobber> X<read-write> X<clobbering> X<truncate> X<truncating> 606 607 Because you're using something like this, which truncates the file and 608 I<then> gives you read-write access: 609 610 open(FH, "+> /path/name"); # WRONG (almost always) 611 612 Whoops. You should instead use this, which will fail if the file 613 doesn't exist. 614 615 open(FH, "+< /path/name"); # open for update 616 617 Using ">" always clobbers or creates. Using "<" never does 618 either. The "+" doesn't change this. 619 620 Here are examples of many kinds of file opens. Those using sysopen() 621 all assume 622 623 use Fcntl; 624 625 To open file for reading: 626 627 open(FH, "< $path") || die $!; 628 sysopen(FH, $path, O_RDONLY) || die $!; 629 630 To open file for writing, create new file if needed or else truncate old file: 631 632 open(FH, "> $path") || die $!; 633 sysopen(FH, $path, O_WRONLY|O_TRUNC|O_CREAT) || die $!; 634 sysopen(FH, $path, O_WRONLY|O_TRUNC|O_CREAT, 0666) || die $!; 635 636 To open file for writing, create new file, file must not exist: 637 638 sysopen(FH, $path, O_WRONLY|O_EXCL|O_CREAT) || die $!; 639 sysopen(FH, $path, O_WRONLY|O_EXCL|O_CREAT, 0666) || die $!; 640 641 To open file for appending, create if necessary: 642 643 open(FH, ">> $path") || die $!; 644 sysopen(FH, $path, O_WRONLY|O_APPEND|O_CREAT) || die $!; 645 sysopen(FH, $path, O_WRONLY|O_APPEND|O_CREAT, 0666) || die $!; 646 647 To open file for appending, file must exist: 648 649 sysopen(FH, $path, O_WRONLY|O_APPEND) || die $!; 650 651 To open file for update, file must exist: 652 653 open(FH, "+< $path") || die $!; 654 sysopen(FH, $path, O_RDWR) || die $!; 655 656 To open file for update, create file if necessary: 657 658 sysopen(FH, $path, O_RDWR|O_CREAT) || die $!; 659 sysopen(FH, $path, O_RDWR|O_CREAT, 0666) || die $!; 660 661 To open file for update, file must not exist: 662 663 sysopen(FH, $path, O_RDWR|O_EXCL|O_CREAT) || die $!; 664 sysopen(FH, $path, O_RDWR|O_EXCL|O_CREAT, 0666) || die $!; 665 666 To open a file without blocking, creating if necessary: 667 668 sysopen(FH, "/foo/somefile", O_WRONLY|O_NDELAY|O_CREAT) 669 or die "can't open /foo/somefile: $!": 670 671 Be warned that neither creation nor deletion of files is guaranteed to 672 be an atomic operation over NFS. That is, two processes might both 673 successfully create or unlink the same file! Therefore O_EXCL 674 isn't as exclusive as you might wish. 675 676 See also the new L<perlopentut> if you have it (new for 5.6). 677 678 =head2 Why do I sometimes get an "Argument list too long" when I use E<lt>*E<gt>? 679 X<argument list too long> 680 681 The C<< <> >> operator performs a globbing operation (see above). 682 In Perl versions earlier than v5.6.0, the internal glob() operator forks 683 csh(1) to do the actual glob expansion, but 684 csh can't handle more than 127 items and so gives the error message 685 C<Argument list too long>. People who installed tcsh as csh won't 686 have this problem, but their users may be surprised by it. 687 688 To get around this, either upgrade to Perl v5.6.0 or later, do the glob 689 yourself with readdir() and patterns, or use a module like File::KGlob, 690 one that doesn't use the shell to do globbing. 691 692 =head2 Is there a leak/bug in glob()? 693 X<glob> 694 695 Due to the current implementation on some operating systems, when you 696 use the glob() function or its angle-bracket alias in a scalar 697 context, you may cause a memory leak and/or unpredictable behavior. It's 698 best therefore to use glob() only in list context. 699 700 =head2 How can I open a file with a leading ">" or trailing blanks? 701 X<filename, special characters> 702 703 (contributed by Brian McCauley) 704 705 The special two argument form of Perl's open() function ignores 706 trailing blanks in filenames and infers the mode from certain leading 707 characters (or a trailing "|"). In older versions of Perl this was the 708 only version of open() and so it is prevalent in old code and books. 709 710 Unless you have a particular reason to use the two argument form you 711 should use the three argument form of open() which does not treat any 712 characters in the filename as special. 713 714 open FILE, "<", " file "; # filename is " file " 715 open FILE, ">", ">file"; # filename is ">file" 716 717 =head2 How can I reliably rename a file? 718 X<rename> X<mv> X<move> X<file, rename> X<ren> 719 720 If your operating system supports a proper mv(1) utility or its 721 functional equivalent, this works: 722 723 rename($old, $new) or system("mv", $old, $new); 724 725 It may be more portable to use the File::Copy module instead. 726 You just copy to the new file to the new name (checking return 727 values), then delete the old one. This isn't really the same 728 semantically as a rename(), which preserves meta-information like 729 permissions, timestamps, inode info, etc. 730 731 Newer versions of File::Copy export a move() function. 732 733 =head2 How can I lock a file? 734 X<lock> X<file, lock> X<flock> 735 736 Perl's builtin flock() function (see L<perlfunc> for details) will call 737 flock(2) if that exists, fcntl(2) if it doesn't (on perl version 5.004 and 738 later), and lockf(3) if neither of the two previous system calls exists. 739 On some systems, it may even use a different form of native locking. 740 Here are some gotchas with Perl's flock(): 741 742 =over 4 743 744 =item 1 745 746 Produces a fatal error if none of the three system calls (or their 747 close equivalent) exists. 748 749 =item 2 750 751 lockf(3) does not provide shared locking, and requires that the 752 filehandle be open for writing (or appending, or read/writing). 753 754 =item 3 755 756 Some versions of flock() can't lock files over a network (e.g. on NFS file 757 systems), so you'd need to force the use of fcntl(2) when you build Perl. 758 But even this is dubious at best. See the flock entry of L<perlfunc> 759 and the F<INSTALL> file in the source distribution for information on 760 building Perl to do this. 761 762 Two potentially non-obvious but traditional flock semantics are that 763 it waits indefinitely until the lock is granted, and that its locks are 764 I<merely advisory>. Such discretionary locks are more flexible, but 765 offer fewer guarantees. This means that files locked with flock() may 766 be modified by programs that do not also use flock(). Cars that stop 767 for red lights get on well with each other, but not with cars that don't 768 stop for red lights. See the perlport manpage, your port's specific 769 documentation, or your system-specific local manpages for details. It's 770 best to assume traditional behavior if you're writing portable programs. 771 (If you're not, you should as always feel perfectly free to write 772 for your own system's idiosyncrasies (sometimes called "features"). 773 Slavish adherence to portability concerns shouldn't get in the way of 774 your getting your job done.) 775 776 For more information on file locking, see also 777 L<perlopentut/"File Locking"> if you have it (new for 5.6). 778 779 =back 780 781 =head2 Why can't I just open(FH, "E<gt>file.lock")? 782 X<lock, lockfile race condition> 783 784 A common bit of code B<NOT TO USE> is this: 785 786 sleep(3) while -e "file.lock"; # PLEASE DO NOT USE 787 open(LCK, "> file.lock"); # THIS BROKEN CODE 788 789 This is a classic race condition: you take two steps to do something 790 which must be done in one. That's why computer hardware provides an 791 atomic test-and-set instruction. In theory, this "ought" to work: 792 793 sysopen(FH, "file.lock", O_WRONLY|O_EXCL|O_CREAT) 794 or die "can't open file.lock: $!"; 795 796 except that lamentably, file creation (and deletion) is not atomic 797 over NFS, so this won't work (at least, not every time) over the net. 798 Various schemes involving link() have been suggested, but 799 these tend to involve busy-wait, which is also less than desirable. 800 801 =head2 I still don't get locking. I just want to increment the number in the file. How can I do this? 802 X<counter> X<file, counter> 803 804 Didn't anyone ever tell you web-page hit counters were useless? 805 They don't count number of hits, they're a waste of time, and they serve 806 only to stroke the writer's vanity. It's better to pick a random number; 807 they're more realistic. 808 809 Anyway, this is what you can do if you can't help yourself. 810 811 use Fcntl qw(:DEFAULT :flock); 812 sysopen(FH, "numfile", O_RDWR|O_CREAT) or die "can't open numfile: $!"; 813 flock(FH, LOCK_EX) or die "can't flock numfile: $!"; 814 $num = <FH> || 0; 815 seek(FH, 0, 0) or die "can't rewind numfile: $!"; 816 truncate(FH, 0) or die "can't truncate numfile: $!"; 817 (print FH $num+1, "\n") or die "can't write numfile: $!"; 818 close FH or die "can't close numfile: $!"; 819 820 Here's a much better web-page hit counter: 821 822 $hits = int( (time() - 850_000_000) / rand(1_000) ); 823 824 If the count doesn't impress your friends, then the code might. :-) 825 826 =head2 All I want to do is append a small amount of text to the end of a file. Do I still have to use locking? 827 X<append> X<file, append> 828 829 If you are on a system that correctly implements flock() and you use the 830 example appending code from "perldoc -f flock" everything will be OK 831 even if the OS you are on doesn't implement append mode correctly (if 832 such a system exists.) So if you are happy to restrict yourself to OSs 833 that implement flock() (and that's not really much of a restriction) 834 then that is what you should do. 835 836 If you know you are only going to use a system that does correctly 837 implement appending (i.e. not Win32) then you can omit the seek() from 838 the code in the previous answer. 839 840 If you know you are only writing code to run on an OS and filesystem that 841 does implement append mode correctly (a local filesystem on a modern 842 Unix for example), and you keep the file in block-buffered mode and you 843 write less than one buffer-full of output between each manual flushing 844 of the buffer then each bufferload is almost guaranteed to be written to 845 the end of the file in one chunk without getting intermingled with 846 anyone else's output. You can also use the syswrite() function which is 847 simply a wrapper around your systems write(2) system call. 848 849 There is still a small theoretical chance that a signal will interrupt 850 the system level write() operation before completion. There is also a 851 possibility that some STDIO implementations may call multiple system 852 level write()s even if the buffer was empty to start. There may be some 853 systems where this probability is reduced to zero. 854 855 =head2 How do I randomly update a binary file? 856 X<file, binary patch> 857 858 If you're just trying to patch a binary, in many cases something as 859 simple as this works: 860 861 perl -i -pe 's{window manager}{window mangler}g' /usr/bin/emacs 862 863 However, if you have fixed sized records, then you might do something more 864 like this: 865 866 $RECSIZE = 220; # size of record, in bytes 867 $recno = 37; # which record to update 868 open(FH, "+<somewhere") || die "can't update somewhere: $!"; 869 seek(FH, $recno * $RECSIZE, 0); 870 read(FH, $record, $RECSIZE) == $RECSIZE || die "can't read record $recno: $!"; 871 # munge the record 872 seek(FH, -$RECSIZE, 1); 873 print FH $record; 874 close FH; 875 876 Locking and error checking are left as an exercise for the reader. 877 Don't forget them or you'll be quite sorry. 878 879 =head2 How do I get a file's timestamp in perl? 880 X<timestamp> X<file, timestamp> 881 882 If you want to retrieve the time at which the file was last 883 read, written, or had its meta-data (owner, etc) changed, 884 you use the B<-A>, B<-M>, or B<-C> file test operations as 885 documented in L<perlfunc>. These retrieve the age of the 886 file (measured against the start-time of your program) in 887 days as a floating point number. Some platforms may not have 888 all of these times. See L<perlport> for details. To 889 retrieve the "raw" time in seconds since the epoch, you 890 would call the stat function, then use localtime(), 891 gmtime(), or POSIX::strftime() to convert this into 892 human-readable form. 893 894 Here's an example: 895 896 $write_secs = (stat($file))[9]; 897 printf "file %s updated at %s\n", $file, 898 scalar localtime($write_secs); 899 900 If you prefer something more legible, use the File::stat module 901 (part of the standard distribution in version 5.004 and later): 902 903 # error checking left as an exercise for reader. 904 use File::stat; 905 use Time::localtime; 906 $date_string = ctime(stat($file)->mtime); 907 print "file $file updated at $date_string\n"; 908 909 The POSIX::strftime() approach has the benefit of being, 910 in theory, independent of the current locale. See L<perllocale> 911 for details. 912 913 =head2 How do I set a file's timestamp in perl? 914 X<timestamp> X<file, timestamp> 915 916 You use the utime() function documented in L<perlfunc/utime>. 917 By way of example, here's a little program that copies the 918 read and write times from its first argument to all the rest 919 of them. 920 921 if (@ARGV < 2) { 922 die "usage: cptimes timestamp_file other_files ...\n"; 923 } 924 $timestamp = shift; 925 ($atime, $mtime) = (stat($timestamp))[8,9]; 926 utime $atime, $mtime, @ARGV; 927 928 Error checking is, as usual, left as an exercise for the reader. 929 930 The perldoc for utime also has an example that has the same 931 effect as touch(1) on files that I<already exist>. 932 933 Certain file systems have a limited ability to store the times 934 on a file at the expected level of precision. For example, the 935 FAT and HPFS filesystem are unable to create dates on files with 936 a finer granularity than two seconds. This is a limitation of 937 the filesystems, not of utime(). 938 939 =head2 How do I print to more than one file at once? 940 X<print, to multiple files> 941 942 To connect one filehandle to several output filehandles, 943 you can use the IO::Tee or Tie::FileHandle::Multiplex modules. 944 945 If you only have to do this once, you can print individually 946 to each filehandle. 947 948 for $fh (FH1, FH2, FH3) { print $fh "whatever\n" } 949 950 =head2 How can I read in an entire file all at once? 951 X<slurp> X<file, slurping> 952 953 You can use the File::Slurp module to do it in one step. 954 955 use File::Slurp; 956 957 $all_of_it = read_file($filename); # entire file in scalar 958 @all_lines = read_file($filename); # one line perl element 959 960 The customary Perl approach for processing all the lines in a file is to 961 do so one line at a time: 962 963 open (INPUT, $file) || die "can't open $file: $!"; 964 while (<INPUT>) { 965 chomp; 966 # do something with $_ 967 } 968 close(INPUT) || die "can't close $file: $!"; 969 970 This is tremendously more efficient than reading the entire file into 971 memory as an array of lines and then processing it one element at a time, 972 which is often--if not almost always--the wrong approach. Whenever 973 you see someone do this: 974 975 @lines = <INPUT>; 976 977 you should think long and hard about why you need everything loaded at 978 once. It's just not a scalable solution. You might also find it more 979 fun to use the standard Tie::File module, or the DB_File module's 980 $DB_RECNO bindings, which allow you to tie an array to a file so that 981 accessing an element the array actually accesses the corresponding 982 line in the file. 983 984 You can read the entire filehandle contents into a scalar. 985 986 { 987 local(*INPUT, $/); 988 open (INPUT, $file) || die "can't open $file: $!"; 989 $var = <INPUT>; 990 } 991 992 That temporarily undefs your record separator, and will automatically 993 close the file at block exit. If the file is already open, just use this: 994 995 $var = do { local $/; <INPUT> }; 996 997 For ordinary files you can also use the read function. 998 999 read( INPUT, $var, -s INPUT ); 1000 1001 The third argument tests the byte size of the data on the INPUT filehandle 1002 and reads that many bytes into the buffer $var. 1003 1004 =head2 How can I read in a file by paragraphs? 1005 X<file, reading by paragraphs> 1006 1007 Use the C<$/> variable (see L<perlvar> for details). You can either 1008 set it to C<""> to eliminate empty paragraphs (C<"abc\n\n\n\ndef">, 1009 for instance, gets treated as two paragraphs and not three), or 1010 C<"\n\n"> to accept empty paragraphs. 1011 1012 Note that a blank line must have no blanks in it. Thus 1013 S<C<"fred\n \nstuff\n\n">> is one paragraph, but C<"fred\n\nstuff\n\n"> is two. 1014 1015 =head2 How can I read a single character from a file? From the keyboard? 1016 X<getc> X<file, reading one character at a time> 1017 1018 You can use the builtin C<getc()> function for most filehandles, but 1019 it won't (easily) work on a terminal device. For STDIN, either use 1020 the Term::ReadKey module from CPAN or use the sample code in 1021 L<perlfunc/getc>. 1022 1023 If your system supports the portable operating system programming 1024 interface (POSIX), you can use the following code, which you'll note 1025 turns off echo processing as well. 1026 1027 #!/usr/bin/perl -w 1028 use strict; 1029 $| = 1; 1030 for (1..4) { 1031 my $got; 1032 print "gimme: "; 1033 $got = getone(); 1034 print "--> $got\n"; 1035 } 1036 exit; 1037 1038 BEGIN { 1039 use POSIX qw(:termios_h); 1040 1041 my ($term, $oterm, $echo, $noecho, $fd_stdin); 1042 1043 $fd_stdin = fileno(STDIN); 1044 1045 $term = POSIX::Termios->new(); 1046 $term->getattr($fd_stdin); 1047 $oterm = $term->getlflag(); 1048 1049 $echo = ECHO | ECHOK | ICANON; 1050 $noecho = $oterm & ~$echo; 1051 1052 sub cbreak { 1053 $term->setlflag($noecho); 1054 $term->setcc(VTIME, 1); 1055 $term->setattr($fd_stdin, TCSANOW); 1056 } 1057 1058 sub cooked { 1059 $term->setlflag($oterm); 1060 $term->setcc(VTIME, 0); 1061 $term->setattr($fd_stdin, TCSANOW); 1062 } 1063 1064 sub getone { 1065 my $key = ''; 1066 cbreak(); 1067 sysread(STDIN, $key, 1); 1068 cooked(); 1069 return $key; 1070 } 1071 1072 } 1073 1074 END { cooked() } 1075 1076 The Term::ReadKey module from CPAN may be easier to use. Recent versions 1077 include also support for non-portable systems as well. 1078 1079 use Term::ReadKey; 1080 open(TTY, "</dev/tty"); 1081 print "Gimme a char: "; 1082 ReadMode "raw"; 1083 $key = ReadKey 0, *TTY; 1084 ReadMode "normal"; 1085 printf "\nYou said %s, char number %03d\n", 1086 $key, ord $key; 1087 1088 =head2 How can I tell whether there's a character waiting on a filehandle? 1089 1090 The very first thing you should do is look into getting the Term::ReadKey 1091 extension from CPAN. As we mentioned earlier, it now even has limited 1092 support for non-portable (read: not open systems, closed, proprietary, 1093 not POSIX, not Unix, etc) systems. 1094 1095 You should also check out the Frequently Asked Questions list in 1096 comp.unix.* for things like this: the answer is essentially the same. 1097 It's very system dependent. Here's one solution that works on BSD 1098 systems: 1099 1100 sub key_ready { 1101 my($rin, $nfd); 1102 vec($rin, fileno(STDIN), 1) = 1; 1103 return $nfd = select($rin,undef,undef,0); 1104 } 1105 1106 If you want to find out how many characters are waiting, there's 1107 also the FIONREAD ioctl call to be looked at. The I<h2ph> tool that 1108 comes with Perl tries to convert C include files to Perl code, which 1109 can be C<require>d. FIONREAD ends up defined as a function in the 1110 I<sys/ioctl.ph> file: 1111 1112 require 'sys/ioctl.ph'; 1113 1114 $size = pack("L", 0); 1115 ioctl(FH, FIONREAD(), $size) or die "Couldn't call ioctl: $!\n"; 1116 $size = unpack("L", $size); 1117 1118 If I<h2ph> wasn't installed or doesn't work for you, you can 1119 I<grep> the include files by hand: 1120 1121 % grep FIONREAD /usr/include/*/* 1122 /usr/include/asm/ioctls.h:#define FIONREAD 0x541B 1123 1124 Or write a small C program using the editor of champions: 1125 1126 % cat > fionread.c 1127 #include <sys/ioctl.h> 1128 main() { 1129 printf("%#08x\n", FIONREAD); 1130 } 1131 ^D 1132 % cc -o fionread fionread.c 1133 % ./fionread 1134 0x4004667f 1135 1136 And then hard code it, leaving porting as an exercise to your successor. 1137 1138 $FIONREAD = 0x4004667f; # XXX: opsys dependent 1139 1140 $size = pack("L", 0); 1141 ioctl(FH, $FIONREAD, $size) or die "Couldn't call ioctl: $!\n"; 1142 $size = unpack("L", $size); 1143 1144 FIONREAD requires a filehandle connected to a stream, meaning that sockets, 1145 pipes, and tty devices work, but I<not> files. 1146 1147 =head2 How do I do a C<tail -f> in perl? 1148 X<tail> X<IO::Handle> X<File::Tail> X<clearerr> 1149 1150 First try 1151 1152 seek(GWFILE, 0, 1); 1153 1154 The statement C<seek(GWFILE, 0, 1)> doesn't change the current position, 1155 but it does clear the end-of-file condition on the handle, so that the 1156 next C<< <GWFILE> >> makes Perl try again to read something. 1157 1158 If that doesn't work (it relies on features of your stdio implementation), 1159 then you need something more like this: 1160 1161 for (;;) { 1162 for ($curpos = tell(GWFILE); <GWFILE>; $curpos = tell(GWFILE)) { 1163 # search for some stuff and put it into files 1164 } 1165 # sleep for a while 1166 seek(GWFILE, $curpos, 0); # seek to where we had been 1167 } 1168 1169 If this still doesn't work, look into the C<clearerr> method 1170 from C<IO::Handle>, which resets the error and end-of-file states 1171 on the handle. 1172 1173 There's also a C<File::Tail> module from CPAN. 1174 1175 =head2 How do I dup() a filehandle in Perl? 1176 X<dup> 1177 1178 If you check L<perlfunc/open>, you'll see that several of the ways 1179 to call open() should do the trick. For example: 1180 1181 open(LOG, ">>/foo/logfile"); 1182 open(STDERR, ">&LOG"); 1183 1184 Or even with a literal numeric descriptor: 1185 1186 $fd = $ENV{MHCONTEXTFD}; 1187 open(MHCONTEXT, "<&=$fd"); # like fdopen(3S) 1188 1189 Note that "<&STDIN" makes a copy, but "<&=STDIN" make 1190 an alias. That means if you close an aliased handle, all 1191 aliases become inaccessible. This is not true with 1192 a copied one. 1193 1194 Error checking, as always, has been left as an exercise for the reader. 1195 1196 =head2 How do I close a file descriptor by number? 1197 X<file, closing file descriptors> X<POSIX> X<close> 1198 1199 If, for some reason, you have a file descriptor instead of a 1200 filehandle (perhaps you used C<POSIX::open>), you can use the 1201 C<close()> function from the C<POSIX> module: 1202 1203 use POSIX (); 1204 1205 POSIX::close( $fd ); 1206 1207 This should rarely be necessary, as the Perl C<close()> function is to be 1208 used for things that Perl opened itself, even if it was a dup of a 1209 numeric descriptor as with C<MHCONTEXT> above. But if you really have 1210 to, you may be able to do this: 1211 1212 require 'sys/syscall.ph'; 1213 $rc = syscall(&SYS_close, $fd + 0); # must force numeric 1214 die "can't sysclose $fd: $!" unless $rc == -1; 1215 1216 Or, just use the fdopen(3S) feature of C<open()>: 1217 1218 { 1219 open my( $fh ), "<&=$fd" or die "Cannot reopen fd=$fd: $!"; 1220 close $fh; 1221 } 1222 1223 =head2 Why can't I use "C:\temp\foo" in DOS paths? Why doesn't `C:\temp\foo.exe` work? 1224 X<filename, DOS issues> 1225 1226 Whoops! You just put a tab and a formfeed into that filename! 1227 Remember that within double quoted strings ("like\this"), the 1228 backslash is an escape character. The full list of these is in 1229 L<perlop/Quote and Quote-like Operators>. Unsurprisingly, you don't 1230 have a file called "c:(tab)emp(formfeed)oo" or 1231 "c:(tab)emp(formfeed)oo.exe" on your legacy DOS filesystem. 1232 1233 Either single-quote your strings, or (preferably) use forward slashes. 1234 Since all DOS and Windows versions since something like MS-DOS 2.0 or so 1235 have treated C</> and C<\> the same in a path, you might as well use the 1236 one that doesn't clash with Perl--or the POSIX shell, ANSI C and C++, 1237 awk, Tcl, Java, or Python, just to mention a few. POSIX paths 1238 are more portable, too. 1239 1240 =head2 Why doesn't glob("*.*") get all the files? 1241 X<glob> 1242 1243 Because even on non-Unix ports, Perl's glob function follows standard 1244 Unix globbing semantics. You'll need C<glob("*")> to get all (non-hidden) 1245 files. This makes glob() portable even to legacy systems. Your 1246 port may include proprietary globbing functions as well. Check its 1247 documentation for details. 1248 1249 =head2 Why does Perl let me delete read-only files? Why does C<-i> clobber protected files? Isn't this a bug in Perl? 1250 1251 This is elaborately and painstakingly described in the 1252 F<file-dir-perms> article in the "Far More Than You Ever Wanted To 1253 Know" collection in http://www.cpan.org/misc/olddoc/FMTEYEWTK.tgz . 1254 1255 The executive summary: learn how your filesystem works. The 1256 permissions on a file say what can happen to the data in that file. 1257 The permissions on a directory say what can happen to the list of 1258 files in that directory. If you delete a file, you're removing its 1259 name from the directory (so the operation depends on the permissions 1260 of the directory, not of the file). If you try to write to the file, 1261 the permissions of the file govern whether you're allowed to. 1262 1263 =head2 How do I select a random line from a file? 1264 X<file, selecting a random line> 1265 1266 Here's an algorithm from the Camel Book: 1267 1268 srand; 1269 rand($.) < 1 && ($line = $_) while <>; 1270 1271 This has a significant advantage in space over reading the whole file 1272 in. You can find a proof of this method in I<The Art of Computer 1273 Programming>, Volume 2, Section 3.4.2, by Donald E. Knuth. 1274 1275 You can use the File::Random module which provides a function 1276 for that algorithm: 1277 1278 use File::Random qw/random_line/; 1279 my $line = random_line($filename); 1280 1281 Another way is to use the Tie::File module, which treats the entire 1282 file as an array. Simply access a random array element. 1283 1284 =head2 Why do I get weird spaces when I print an array of lines? 1285 1286 Saying 1287 1288 print "@lines\n"; 1289 1290 joins together the elements of C<@lines> with a space between them. 1291 If C<@lines> were C<("little", "fluffy", "clouds")> then the above 1292 statement would print 1293 1294 little fluffy clouds 1295 1296 but if each element of C<@lines> was a line of text, ending a newline 1297 character C<("little\n", "fluffy\n", "clouds\n")> then it would print: 1298 1299 little 1300 fluffy 1301 clouds 1302 1303 If your array contains lines, just print them: 1304 1305 print @lines; 1306 1307 =head1 REVISION 1308 1309 Revision: $Revision: 10126 $ 1310 1311 Date: $Date: 2007-10-27 21:29:20 +0200 (Sat, 27 Oct 2007) $ 1312 1313 See L<perlfaq> for source control details and availability. 1314 1315 =head1 AUTHOR AND COPYRIGHT 1316 1317 Copyright (c) 1997-2007 Tom Christiansen, Nathan Torkington, and 1318 other authors as noted. All rights reserved. 1319 1320 This documentation is free; you can redistribute it and/or modify it 1321 under the same terms as Perl itself. 1322 1323 Irrespective of its distribution, all code examples here are in the public 1324 domain. You are permitted and encouraged to use this code and any 1325 derivatives thereof in your own programs for fun or for profit as you 1326 see fit. A simple comment in the code giving credit to the FAQ would 1327 be courteous but is not required.
title
Description
Body
title
Description
Body
title
Description
Body
title
Body
| Generated: Tue Mar 17 22:47:18 2015 | Cross-referenced by PHPXref 0.7.1 |