5 File::Temp - return name and handle of a temporary file safely
11 This module is designed to be portable across operating systems
12 and it currently supports Unix, VMS, DOS, OS/2 and Windows. When
13 porting to a new OS there are generally three main issues
14 that have to be solved:
20 Can the OS unlink an open file? If it can not then the
21 C<_can_unlink_opened_file> method should be modified.
25 Are the return values from C<stat> reliable? By default all the
26 return values from C<stat> are compared when unlinking a temporary
27 file using the filename and the handle. Operating systems other than
28 unix do not always have valid entries in all fields. If C<unlink0> fails
29 then the C<stat> comparison should be modified accordingly.
33 Security. Systems that can not support a test for the sticky bit
34 on a directory can not use the MEDIUM and HIGH security tests.
35 The C<_can_do_level> method should be modified accordingly.
43 use File::Temp qw/ tempfile tempdir /;
45 $dir = tempdir( CLEANUP => 1 );
46 ($fh, $filename) = tempfile( DIR => $dir );
48 ($fh, $filename) = tempfile( $template, DIR => $dir);
49 ($fh, $filename) = tempfile( $template, SUFFIX => '.dat');
55 use File::Temp qw/ :mktemp /;
57 ($fh, $file) = mkstemp( "tmpfileXXXXX" );
58 ($fh, $file) = mkstemps( "tmpfileXXXXXX", $suffix);
60 $tmpdir = mkdtemp( $template );
62 $unopened_file = mktemp( $template );
66 use File::Temp qw/ :POSIX /;
71 ($fh, $file) = tmpnam();
72 ($fh, $file) = tmpfile();
75 Compatibility functions:
77 $unopened_file = File::Temp::tempnam( $dir, $pfx );
81 Objects (NOT YET IMPLEMENTED):
85 $fh = new File::Temp($template);
86 $fname = $fh->filename;
92 C<File::Temp> can be used to create and open temporary files in a safe way.
93 The tempfile() function can be used to return the name and the open
94 filehandle of a temporary file. The tempdir() function can
95 be used to create a temporary directory.
97 The security aspect of temporary file creation is emphasized such that
98 a filehandle and filename are returned together. This helps guarantee
99 that a race condition can not occur where the temporary file is
100 created by another process between checking for the existence of the
101 file and its opening. Additional security levels are provided to
102 check, for example, that the sticky bit is set on world writable
103 directories. See L<"safe_level"> for more information.
105 For compatibility with popular C library functions, Perl implementations of
106 the mkstemp() family of functions are provided. These are, mkstemp(),
107 mkstemps(), mkdtemp() and mktemp().
109 Additionally, implementations of the standard L<POSIX|POSIX>
110 tmpnam() and tmpfile() functions are provided if required.
112 Implementations of mktemp(), tmpnam(), and tempnam() are provided,
113 but should be used with caution since they return only a filename
114 that was valid when function was called, so cannot guarantee
115 that the file will not exist by the time the caller opens the filename.
119 # 5.6.0 gives us S_IWOTH, S_IWGRP, our and auto-vivifying filehandls
120 # People would like a version on 5.005 so give them what they want :-)
125 use File::Path qw/ rmtree /;
128 require VMS::Stdio if $^O eq 'VMS';
130 # Need the Symbol package if we are running older perl
131 require Symbol if $] < 5.006;
134 # use 'our' on v5.6.0
135 use vars qw($VERSION @EXPORT_OK %EXPORT_TAGS $DEBUG);
139 # We are exporting functions
141 use base qw/Exporter/;
143 # Export list - to allow fine tuning of export table
157 # Groups of functions for export
160 'POSIX' => [qw/ tmpnam tmpfile /],
161 'mktemp' => [qw/ mktemp mkstemp mkstemps mkdtemp/],
164 # add contents of these tags to @EXPORT
165 Exporter::export_tags('POSIX','mktemp');
171 # This is a list of characters that can be used in random filenames
173 my @CHARS = (qw/ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
174 a b c d e f g h i j k l m n o p q r s t u v w x y z
175 0 1 2 3 4 5 6 7 8 9 _
178 # Maximum number of tries to make a temp file before failing
180 use constant MAX_TRIES => 10;
182 # Minimum number of X characters that should be in a template
183 use constant MINX => 4;
185 # Default template when no template supplied
187 use constant TEMPXXX => 'X' x 10;
189 # Constants for the security level
191 use constant STANDARD => 0;
192 use constant MEDIUM => 1;
193 use constant HIGH => 2;
195 # OPENFLAGS. If we defined the flag to use with Sysopen here this gives
196 # us an optimisation when many temporary files are requested
198 my $OPENFLAGS = O_CREAT | O_EXCL | O_RDWR;
200 for my $oflag (qw/ FOLLOW BINARY LARGEFILE EXLOCK NOINHERIT /) {
201 my ($bit, $func) = (0, "Fcntl::O_" . $oflag);
203 $OPENFLAGS |= $bit if eval {
204 # Make sure that redefined die handlers do not cause problems
206 local $SIG{__DIE__} = sub {};
207 local $SIG{__WARN__} = sub {};
213 # On some systems the O_TEMPORARY flag can be used to tell the OS
214 # to automatically remove the file when it is closed. This is fine
215 # in most cases but not if tempfile is called with UNLINK=>0 and
216 # the filename is requested -- in the case where the filename is to
217 # be passed to another routine. This happens on windows. We overcome
218 # this by using a second open flags variable
220 my $OPENTEMPFLAGS = $OPENFLAGS;
221 for my $oflag (qw/ TEMPORARY /) {
222 my ($bit, $func) = (0, "Fcntl::O_" . $oflag);
224 $OPENTEMPFLAGS |= $bit if eval {
225 # Make sure that redefined die handlers do not cause problems
227 local $SIG{__DIE__} = sub {};
228 local $SIG{__WARN__} = sub {};
234 # INTERNAL ROUTINES - not to be used outside of package
236 # Generic routine for getting a temporary filename
237 # modelled on OpenBSD _gettemp() in mktemp.c
239 # The template must contain X's that are to be replaced
240 # with the random values
244 # TEMPLATE - string containing the XXXXX's that is converted
245 # to a random filename and opened if required
247 # Optionally, a hash can also be supplied containing specific options
248 # "open" => if true open the temp file, else just return the name
250 # "mkdir"=> if true, we are creating a temp directory rather than tempfile
252 # "suffixlen" => number of characters at end of PATH to be ignored.
254 # "unlink_on_close" => indicates that, if possible, the OS should remove
255 # the file as soon as it is closed. Usually indicates
256 # use of the O_TEMPORARY flag to sysopen.
257 # Usually irrelevant on unix
259 # Optionally a reference to a scalar can be passed into the function
260 # On error this will be used to store the reason for the error
261 # "ErrStr" => \$errstr
262 # "open" and "mkdir" can not both be true
263 # "unlink_on_close" is not used when "mkdir" is true.
265 # The default options are equivalent to mktemp().
268 # filehandle - open file handle (if called with doopen=1, else undef)
269 # temp name - name of the temp file or directory
272 # ($fh, $name) = _gettemp($template, "open" => 1);
274 # for the current version, failures are associated with
275 # stored in an error string and returned to give the reason whilst debugging
276 # This routine is not called by any external function
279 croak 'Usage: ($fh, $name) = _gettemp($template, OPTIONS);'
280 unless scalar(@_) >= 1;
282 # the internal error string - expect it to be overridden
283 # Need this in case the caller decides not to supply us a value
284 # need an anonymous scalar
291 "unlink_on_close" => 0,
292 "ErrStr" => \$tempErrStr,
296 my $template = shift;
297 if (ref($template)) {
298 # Use a warning here since we have not yet merged ErrStr
299 carp "File::Temp::_gettemp: template must not be a reference";
303 # Check that the number of entries on stack are even
304 if (scalar(@_) % 2 != 0) {
305 # Use a warning here since we have not yet merged ErrStr
306 carp "File::Temp::_gettemp: Must have even number of options";
310 # Read the options and merge with defaults
311 %options = (%options, @_) if @_;
313 # Make sure the error string is set to undef
314 ${$options{ErrStr}} = undef;
315 # Can not open the file and make a directory in a single call
316 if ($options{"open"} && $options{"mkdir"}) {
317 ${$options{ErrStr}} = "doopen and domkdir can not both be true\n";
321 # Find the start of the end of the Xs (position of last X)
322 # Substr starts from 0
323 my $start = length($template) - 1 - $options{"suffixlen"};
325 # Check that we have at least MINX x X (eg 'XXXX") at the end of the string
326 # (taking suffixlen into account). Any fewer is insecure.
328 # Do it using substr - no reason to use a pattern match since
329 # we know where we are looking and what we are looking for
331 if (substr($template, $start - MINX + 1, MINX) ne 'X' x MINX) {
332 ${$options{ErrStr}} = "The template must contain at least ".
333 MINX . " 'X' characters\n";
337 # Replace all the X at the end of the substring with a
338 # random character or just all the XX at the end of a full string.
339 # Do it as an if, since the suffix adjusts which section to replace
340 # and suffixlen=0 returns nothing if used in the substr directly
341 # and generate a full path from the template
343 my $path = _replace_XX($template, $options{"suffixlen"});
346 # Split the path into constituent parts - eventually we need to check
347 # whether the directory exists
348 # We need to know whether we are making a temp directory
351 my ($volume, $directories, $file);
352 my $parent; # parent directory
353 if ($options{"mkdir"}) {
354 # There is no filename at the end
355 ($volume, $directories, $file) = File::Spec->splitpath( $path, 1);
357 # The parent is then $directories without the last directory
358 # Split the directory and put it back together again
359 my @dirs = File::Spec->splitdir($directories);
361 # If @dirs only has one entry that means we are in the current
364 $parent = File::Spec->curdir;
367 if ($^O eq 'VMS') { # need volume to avoid relative dir spec
368 $parent = File::Spec->catdir($volume, @dirs[0..$#dirs-1]);
369 $parent = 'sys$disk:[]' if $parent eq '';
372 # Put it back together without the last one
373 $parent = File::Spec->catdir(@dirs[0..$#dirs-1]);
375 # ...and attach the volume (no filename)
376 $parent = File::Spec->catpath($volume, $parent, '');
383 # Get rid of the last filename (use File::Basename for this?)
384 ($volume, $directories, $file) = File::Spec->splitpath( $path );
386 # Join up without the file part
387 $parent = File::Spec->catpath($volume,$directories,'');
389 # If $parent is empty replace with curdir
390 $parent = File::Spec->curdir
391 unless $directories ne '';
395 # Check that the parent directories exist
396 # Do this even for the case where we are simply returning a name
397 # not a file -- no point returning a name that includes a directory
398 # that does not exist or is not writable
400 unless (-d $parent) {
401 ${$options{ErrStr}} = "Parent directory ($parent) is not a directory";
405 ${$options{ErrStr}} = "Parent directory ($parent) is not writable\n";
409 # Check the stickiness of the directory and chown giveaway if required
410 # If the directory is world writable the sticky bit
413 if (File::Temp->safe_level == MEDIUM) {
415 unless (_is_safe($parent,\$safeerr)) {
416 ${$options{ErrStr}} = "Parent directory ($parent) is not safe ($safeerr)";
419 } elsif (File::Temp->safe_level == HIGH) {
421 unless (_is_verysafe($parent, \$safeerr)) {
422 ${$options{ErrStr}} = "Parent directory ($parent) is not safe ($safeerr)";
428 # Now try MAX_TRIES time to open the file
429 for (my $i = 0; $i < MAX_TRIES; $i++) {
431 # Try to open the file if requested
432 if ($options{"open"}) {
435 # If we are running before perl5.6.0 we can not auto-vivify
437 $fh = &Symbol::gensym;
440 # Try to make sure this will be marked close-on-exec
441 # XXX: Win32 doesn't respect this, nor the proper fcntl,
442 # but may have O_NOINHERIT. This may or may not be in Fcntl.
445 # Store callers umask
451 # Attempt to open the file
452 my $open_success = undef;
453 if ( $^O eq 'VMS' and $options{"unlink_on_close"} ) {
454 # make it auto delete on close by setting FAB$V_DLT bit
455 $fh = VMS::Stdio::vmssysopen($path, $OPENFLAGS, 0600, 'fop=dlt');
458 my $flags = ( $options{"unlink_on_close"} ?
461 $open_success = sysopen($fh, $path, $flags, 0600);
463 if ( $open_success ) {
468 # Opened successfully - return file handle and name
475 # Error opening file - abort with error
476 # if the reason was anything but EEXIST
477 unless ($!{EEXIST}) {
478 ${$options{ErrStr}} = "Could not create temp file $path: $!";
482 # Loop round for another try
485 } elsif ($options{"mkdir"}) {
487 # Store callers umask
493 # Open the temp directory
494 if (mkdir( $path, 0700)) {
505 # Abort with error if the reason for failure was anything
507 unless ($!{EEXIST}) {
508 ${$options{ErrStr}} = "Could not create directory $path: $!";
512 # Loop round for another try
518 # Return true if the file can not be found
519 # Directory has been checked previously
521 return (undef, $path) unless -e $path;
523 # Try again until MAX_TRIES
527 # Did not successfully open the tempfile/dir
528 # so try again with a different set of random letters
529 # No point in trying to increment unless we have only
530 # 1 X say and the randomness could come up with the same
531 # file MAX_TRIES in a row.
533 # Store current attempt - in principal this implies that the
534 # 3rd time around the open attempt that the first temp file
535 # name could be generated again. Probably should store each
536 # attempt and make sure that none are repeated
538 my $original = $path;
539 my $counter = 0; # Stop infinite loop
544 # Generate new name from original template
545 $path = _replace_XX($template, $options{"suffixlen"});
549 } until ($path ne $original || $counter > $MAX_GUESS);
551 # Check for out of control looping
552 if ($counter > $MAX_GUESS) {
553 ${$options{ErrStr}} = "Tried to get a new temp name different to the previous value $MAX_GUESS times.\nSomething wrong with template?? ($template)";
559 # If we get here, we have run out of tries
560 ${ $options{ErrStr} } = "Have exceeded the maximum number of attempts ("
561 . MAX_TRIES . ") to open temp file/dir";
567 # Internal routine to return a random character from the
568 # character list. Does not do an srand() since rand()
569 # will do one automatically
571 # No arguments. Return value is the random character
573 # No longer called since _replace_XX runs a few percent faster if
574 # I inline the code. This is important if we are creating thousands of
579 $CHARS[ int( rand( $#CHARS ) ) ];
583 # Internal routine to replace the XXXX... with random characters
584 # This has to be done by _gettemp() every time it fails to
585 # open a temp file/dir
587 # Arguments: $template (the template with XXX),
588 # $ignore (number of characters at end to ignore)
590 # Returns: modified template
594 croak 'Usage: _replace_XX($template, $ignore)'
595 unless scalar(@_) == 2;
597 my ($path, $ignore) = @_;
599 # Do it as an if, since the suffix adjusts which section to replace
600 # and suffixlen=0 returns nothing if used in the substr directly
601 # Alternatively, could simply set $ignore to length($path)-1
602 # Don't want to always use substr when not required though.
605 substr($path, 0, - $ignore) =~ s/X(?=X*\z)/$CHARS[ int( rand( $#CHARS ) ) ]/ge;
607 $path =~ s/X(?=X*\z)/$CHARS[ int( rand( $#CHARS ) ) ]/ge;
613 # internal routine to check to see if the directory is safe
614 # First checks to see if the directory is not owned by the
615 # current user or root. Then checks to see if anyone else
616 # can write to the directory and if so, checks to see if
617 # it has the sticky bit set
619 # Will not work on systems that do not support sticky bit
621 #Args: directory path to check
622 # Optionally: reference to scalar to contain error message
623 # Returns true if the path is safe and false otherwise.
624 # Returns undef if can not even run stat() on the path
626 # This routine based on version written by Tom Christiansen
628 # Presumably, by the time we actually attempt to create the
629 # file or directory in this directory, it may not be safe
630 # anymore... Have to run _is_safe directly after the open.
638 my @info = stat($path);
639 unless (scalar(@info)) {
640 $$err_ref = "stat(path) returned no values";
643 return 1 if $^O eq 'VMS'; # owner delete control at file level
645 # Check to see whether owner is neither superuser (or a system uid) nor me
646 # Use the real uid from the $< variable
648 if ($info[4] > File::Temp->top_system_uid() && $info[4] != $<) {
650 Carp::cluck(sprintf "uid=$info[4] topuid=%s \$<=$< path='$path'",
651 File::Temp->top_system_uid());
653 $$err_ref = "Directory owned neither by root nor the current user"
658 # check whether group or other can write file
659 # use 066 to detect either reading or writing
660 # use 022 to check writability
661 # Do it with S_IWOTH and S_IWGRP for portability (maybe)
663 if (($info[2] & &Fcntl::S_IWGRP) || # Is group writable?
664 ($info[2] & &Fcntl::S_IWOTH) ) { # Is world writable?
665 # Must be a directory
667 $$err_ref = "Path ($path) is not a directory"
671 # Must have sticky bit set
673 $$err_ref = "Sticky bit not set on $path when dir is group|world writable"
682 # Internal routine to check whether a directory is safe
683 # for temp files. Safer than _is_safe since it checks for
684 # the possibility of chown giveaway and if that is a possibility
685 # checks each directory in the path to see if it is safe (with _is_safe)
687 # If _PC_CHOWN_RESTRICTED is not set, does the full test of each
690 # Takes optional second arg as scalar ref to error reason
693 # Need POSIX - but only want to bother if really necessary due to overhead
697 print "_is_verysafe testing $path\n" if $DEBUG;
698 return 1 if $^O eq 'VMS'; # owner delete control at file level
701 # Should Get the value of _PC_CHOWN_RESTRICTED if it is defined
702 # and If it is not there do the extensive test
703 my $chown_restricted;
704 $chown_restricted = &POSIX::_PC_CHOWN_RESTRICTED()
705 if eval { &POSIX::_PC_CHOWN_RESTRICTED(); 1};
707 # If chown_resticted is set to some value we should test it
708 if (defined $chown_restricted) {
710 # Return if the current directory is safe
711 return _is_safe($path,$err_ref) if POSIX::sysconf( $chown_restricted );
715 # To reach this point either, the _PC_CHOWN_RESTRICTED symbol
716 # was not avialable or the symbol was there but chown giveaway
717 # is allowed. Either way, we now have to test the entire tree for
720 # Convert path to an absolute directory if required
721 unless (File::Spec->file_name_is_absolute($path)) {
722 $path = File::Spec->rel2abs($path);
725 # Split directory into components - assume no file
726 my ($volume, $directories, undef) = File::Spec->splitpath( $path, 1);
728 # Slightly less efficient than having a a function in File::Spec
729 # to chop off the end of a directory or even a function that
730 # can handle ../ in a directory tree
731 # Sometimes splitdir() returns a blank at the end
732 # so we will probably check the bottom directory twice in some cases
733 my @dirs = File::Spec->splitdir($directories);
735 # Concatenate one less directory each time around
736 foreach my $pos (0.. $#dirs) {
737 # Get a directory name
738 my $dir = File::Spec->catpath($volume,
739 File::Spec->catdir(@dirs[0.. $#dirs - $pos]),
743 print "TESTING DIR $dir\n" if $DEBUG;
745 # Check the directory
746 return 0 unless _is_safe($dir,$err_ref);
755 # internal routine to determine whether unlink works on this
756 # platform for files that are currently open.
757 # Returns true if we can, false otherwise.
759 # Currently WinNT, OS/2 and VMS can not unlink an opened file
760 # On VMS this is because the O_EXCL flag is used to open the
761 # temporary file. Currently I do not know enough about the issues
762 # on VMS to decide whether O_EXCL is a requirement.
764 sub _can_unlink_opened_file {
766 if ($^O eq 'MSWin32' || $^O eq 'os2' || $^O eq 'VMS' || $^O eq 'dos') {
774 # internal routine to decide which security levels are allowed
775 # see safe_level() for more information on this
777 # Controls whether the supplied security level is allowed
779 # $cando = _can_do_level( $level )
786 # Always have to be able to do STANDARD
787 return 1 if $level == STANDARD;
789 # Currently, the systems that can do HIGH or MEDIUM are identical
790 if ( $^O eq 'MSWin32' || $^O eq 'os2' || $^O eq 'cygwin' || $^O eq 'dos') {
798 # This routine sets up a deferred unlinking of a specified
799 # filename and filehandle. It is used in the following cases:
800 # - Called by unlink0 if an opened file can not be unlinked
801 # - Called by tempfile() if files are to be removed on shutdown
802 # - Called by tempdir() if directories are to be removed on shutdown
805 # _deferred_unlink( $fh, $fname, $isdir );
807 # - filehandle (so that it can be expclicitly closed if open
808 # - filename (the thing we want to remove)
809 # - isdir (flag to indicate that we are being given a directory)
810 # [and hence no filehandle]
812 # Status is not referred to since all the magic is done with an END block
815 # Will set up two lexical variables to contain all the files to be
816 # removed. One array for files, another for directories
817 # They will only exist in this block
818 # This means we only have to set up a single END block to remove all files
819 # @files_to_unlink contains an array ref with the filehandle and filename
820 my (@files_to_unlink, @dirs_to_unlink);
822 # Set up an end block to use these arrays
825 foreach my $file (@files_to_unlink) {
826 # close the filehandle without checking its state
827 # in order to make real sure that this is closed
828 # if its already closed then I dont care about the answer
829 # probably a better way to do this
830 close($file->[0]); # file handle is [0]
832 if (-f $file->[1]) { # file name is [1]
833 unlink $file->[1] or warn "Error removing ".$file->[1];
837 foreach my $dir (@dirs_to_unlink) {
839 rmtree($dir, $DEBUG, 1);
845 # This is the sub called to register a file for deferred unlinking
846 # This could simply store the input parameters and defer everything
847 # until the END block. For now we do a bit of checking at this
848 # point in order to make sure that (1) we have a file/dir to delete
849 # and (2) we have been called with the correct arguments.
850 sub _deferred_unlink {
852 croak 'Usage: _deferred_unlink($fh, $fname, $isdir)'
853 unless scalar(@_) == 3;
855 my ($fh, $fname, $isdir) = @_;
857 warn "Setting up deferred removal of $fname\n"
860 # If we have a directory, check that it is a directory
865 # Directory exists so store it
866 # first on VMS turn []foo into [.foo] for rmtree
867 $fname = VMS::Filespec::vmspath($fname) if $^O eq 'VMS';
868 push (@dirs_to_unlink, $fname);
871 carp "Request to remove directory $fname could not be completed since it does not exist!\n" if $^W;
878 # file exists so store handle and name for later removal
879 push(@files_to_unlink, [$fh, $fname]);
882 carp "Request to remove file $fname could not be completed since it is not there!\n" if $^W;
894 This section describes the recommended interface for generating
895 temporary files and directories.
901 This is the basic function to generate temporary files.
902 The behaviour of the file can be changed using various options:
904 ($fh, $filename) = tempfile();
906 Create a temporary file in the directory specified for temporary
907 files, as specified by the tmpdir() function in L<File::Spec>.
909 ($fh, $filename) = tempfile($template);
911 Create a temporary file in the current directory using the supplied
912 template. Trailing `X' characters are replaced with random letters to
913 generate the filename. At least four `X' characters must be present
916 ($fh, $filename) = tempfile($template, SUFFIX => $suffix)
918 Same as previously, except that a suffix is added to the template
919 after the `X' translation. Useful for ensuring that a temporary
920 filename has a particular extension when needed by other applications.
921 But see the WARNING at the end.
923 ($fh, $filename) = tempfile($template, DIR => $dir);
925 Translates the template as before except that a directory name
928 ($fh, $filename) = tempfile($template, UNLINK => 1);
930 Return the filename and filehandle as before except that the file is
931 automatically removed when the program exits. Default is for the file
932 to be removed if a file handle is requested and to be kept if the
933 filename is requested. In a scalar context (where no filename is
934 returned) the file is always deleted either on exit or when it is closed.
936 If the template is not specified, a template is always
937 automatically generated. This temporary file is placed in tmpdir()
938 (L<File::Spec>) unless a directory is specified explicitly with the
941 $fh = tempfile( $template, DIR => $dir );
943 If called in scalar context, only the filehandle is returned
944 and the file will automatically be deleted when closed (see
945 the description of tmpfile() elsewhere in this document).
946 This is the preferred mode of operation, as if you only
947 have a filehandle, you can never create a race condition
948 by fumbling with the filename. On systems that can not unlink
949 an open file or can not mark a file as temporary when it is opened
950 (for example, Windows NT uses the C<O_TEMPORARY> flag))
951 the file is marked for deletion when the program ends (equivalent
952 to setting UNLINK to 1). The C<UNLINK> flag is ignored if present.
954 (undef, $filename) = tempfile($template, OPEN => 0);
956 This will return the filename based on the template but
957 will not open this file. Cannot be used in conjunction with
958 UNLINK set to true. Default is to always open the file
959 to protect from possible race conditions. A warning is issued
960 if warnings are turned on. Consider using the tmpnam()
961 and mktemp() functions described elsewhere in this document
962 if opening the file is not required.
964 Options can be combined as required.
970 # Can not check for argument count since we can have any
975 "DIR" => undef, # Directory prefix
976 "SUFFIX" => '', # Template suffix
977 "UNLINK" => 0, # Do not unlink file on exit
978 "OPEN" => 1, # Open file
981 # Check to see whether we have an odd or even number of arguments
982 my $template = (scalar(@_) % 2 == 1 ? shift(@_) : undef);
984 # Read the options and merge with defaults
985 %options = (%options, @_) if @_;
987 # First decision is whether or not to open the file
988 if (! $options{"OPEN"}) {
990 warn "tempfile(): temporary filename requested but not opened.\nPossibly unsafe, consider using tempfile() with OPEN set to true\n"
995 if ($options{"DIR"} and $^O eq 'VMS') {
997 # on VMS turn []foo into [.foo] for concatenation
998 $options{"DIR"} = VMS::Filespec::vmspath($options{"DIR"});
1001 # Construct the template
1003 # Have a choice of trying to work around the mkstemp/mktemp/tmpnam etc
1004 # functions or simply constructing a template and using _gettemp()
1005 # explicitly. Go for the latter
1007 # First generate a template if not defined and prefix the directory
1008 # If no template must prefix the temp directory
1009 if (defined $template) {
1010 if ($options{"DIR"}) {
1012 $template = File::Spec->catfile($options{"DIR"}, $template);
1018 if ($options{"DIR"}) {
1020 $template = File::Spec->catfile($options{"DIR"}, TEMPXXX);
1024 $template = File::Spec->catfile(File::Spec->tmpdir, TEMPXXX);
1031 $template .= $options{"SUFFIX"};
1033 # Determine whether we should tell _gettemp to unlink the file
1034 # On unix this is irrelevant and can be worked out after the file is
1035 # opened (simply by unlinking the open filehandle). On Windows or VMS
1036 # we have to indicate temporary-ness when we open the file. In general
1037 # we only want a true temporary file if we are returning just the
1038 # filehandle - if the user wants the filename they probably do not
1039 # want the file to disappear as soon as they close it.
1040 # For this reason, tie unlink_on_close to the return context regardless
1042 my $unlink_on_close = ( wantarray ? 0 : 1);
1045 my ($fh, $path, $errstr);
1046 croak "Error in tempfile() using $template: $errstr"
1047 unless (($fh, $path) = _gettemp($template,
1048 "open" => $options{'OPEN'},
1050 "unlink_on_close" => $unlink_on_close,
1051 "suffixlen" => length($options{'SUFFIX'}),
1052 "ErrStr" => \$errstr,
1055 # Set up an exit handler that can do whatever is right for the
1056 # system. This removes files at exit when requested explicitly or when
1057 # system is asked to unlink_on_close but is unable to do so because
1058 # of OS limitations.
1059 # The latter should be achieved by using a tied filehandle.
1060 # Do not check return status since this is all done with END blocks.
1061 _deferred_unlink($fh, $path, 0) if $options{"UNLINK"};
1066 if ($options{'OPEN'}) {
1067 return ($fh, $path);
1069 return (undef, $path);
1074 # Unlink the file. It is up to unlink0 to decide what to do with
1075 # this (whether to unlink now or to defer until later)
1076 unlink0($fh, $path) or croak "Error unlinking file $path using unlink0";
1078 # Return just the filehandle.
1087 This is the recommended interface for creation of temporary directories.
1088 The behaviour of the function depends on the arguments:
1090 $tempdir = tempdir();
1092 Create a directory in tmpdir() (see L<File::Spec|File::Spec>).
1094 $tempdir = tempdir( $template );
1096 Create a directory from the supplied template. This template is
1097 similar to that described for tempfile(). `X' characters at the end
1098 of the template are replaced with random letters to construct the
1099 directory name. At least four `X' characters must be in the template.
1101 $tempdir = tempdir ( DIR => $dir );
1103 Specifies the directory to use for the temporary directory.
1104 The temporary directory name is derived from an internal template.
1106 $tempdir = tempdir ( $template, DIR => $dir );
1108 Prepend the supplied directory name to the template. The template
1109 should not include parent directory specifications itself. Any parent
1110 directory specifications are removed from the template before
1111 prepending the supplied directory.
1113 $tempdir = tempdir ( $template, TMPDIR => 1 );
1115 Using the supplied template, creat the temporary directory in
1116 a standard location for temporary files. Equivalent to doing
1118 $tempdir = tempdir ( $template, DIR => File::Spec->tmpdir);
1120 but shorter. Parent directory specifications are stripped from the
1121 template itself. The C<TMPDIR> option is ignored if C<DIR> is set
1122 explicitly. Additionally, C<TMPDIR> is implied if neither a template
1123 nor a directory are supplied.
1125 $tempdir = tempdir( $template, CLEANUP => 1);
1127 Create a temporary directory using the supplied template, but
1128 attempt to remove it (and all files inside it) when the program
1129 exits. Note that an attempt will be made to remove all files from
1130 the directory even if they were not created by this module (otherwise
1131 why ask to clean it up?). The directory removal is made with
1132 the rmtree() function from the L<File::Path|File::Path> module.
1133 Of course, if the template is not specified, the temporary directory
1134 will be created in tmpdir() and will also be removed at program exit.
1142 # Can not check for argument count since we can have any
1147 "CLEANUP" => 0, # Remove directory on exit
1148 "DIR" => '', # Root directory
1149 "TMPDIR" => 0, # Use tempdir with template
1152 # Check to see whether we have an odd or even number of arguments
1153 my $template = (scalar(@_) % 2 == 1 ? shift(@_) : undef );
1155 # Read the options and merge with defaults
1156 %options = (%options, @_) if @_;
1158 # Modify or generate the template
1160 # Deal with the DIR and TMPDIR options
1161 if (defined $template) {
1163 # Need to strip directory path if using DIR or TMPDIR
1164 if ($options{'TMPDIR'} || $options{'DIR'}) {
1166 # Strip parent directory from the filename
1168 # There is no filename at the end
1169 $template = VMS::Filespec::vmspath($template) if $^O eq 'VMS';
1170 my ($volume, $directories, undef) = File::Spec->splitpath( $template, 1);
1172 # Last directory is then our template
1173 $template = (File::Spec->splitdir($directories))[-1];
1175 # Prepend the supplied directory or temp dir
1176 if ($options{"DIR"}) {
1178 $template = File::Spec->catdir($options{"DIR"}, $template);
1180 } elsif ($options{TMPDIR}) {
1183 $template = File::Spec->catdir(File::Spec->tmpdir, $template);
1191 if ($options{"DIR"}) {
1193 $template = File::Spec->catdir($options{"DIR"}, TEMPXXX);
1197 $template = File::Spec->catdir(File::Spec->tmpdir, TEMPXXX);
1203 # Create the directory
1206 if ($^O eq 'VMS') { # dir names can end in delimiters
1207 $template =~ m/([\.\]:>]+)$/;
1208 $suffixlen = length($1);
1211 croak "Error in tempdir() using $template: $errstr"
1212 unless ((undef, $tempdir) = _gettemp($template,
1215 "suffixlen" => $suffixlen,
1216 "ErrStr" => \$errstr,
1219 # Install exit handler; must be dynamic to get lexical
1220 if ( $options{'CLEANUP'} && -d $tempdir) {
1221 _deferred_unlink(undef, $tempdir, 1);
1224 # Return the dir name
1231 =head1 MKTEMP FUNCTIONS
1233 The following functions are Perl implementations of the
1234 mktemp() family of temp file generation system calls.
1240 Given a template, returns a filehandle to the temporary file and the name
1243 ($fh, $name) = mkstemp( $template );
1245 In scalar context, just the filehandle is returned.
1247 The template may be any filename with some number of X's appended
1248 to it, for example F</tmp/temp.XXXX>. The trailing X's are replaced
1249 with unique alphanumeric combinations.
1257 croak "Usage: mkstemp(template)"
1260 my $template = shift;
1262 my ($fh, $path, $errstr);
1263 croak "Error in mkstemp using $template: $errstr"
1264 unless (($fh, $path) = _gettemp($template,
1268 "ErrStr" => \$errstr,
1272 return ($fh, $path);
1282 Similar to mkstemp(), except that an extra argument can be supplied
1283 with a suffix to be appended to the template.
1285 ($fh, $name) = mkstemps( $template, $suffix );
1287 For example a template of C<testXXXXXX> and suffix of C<.dat>
1288 would generate a file similar to F<testhGji_w.dat>.
1290 Returns just the filehandle alone when called in scalar context.
1296 croak "Usage: mkstemps(template, suffix)"
1300 my $template = shift;
1303 $template .= $suffix;
1305 my ($fh, $path, $errstr);
1306 croak "Error in mkstemps using $template: $errstr"
1307 unless (($fh, $path) = _gettemp($template,
1310 "suffixlen" => length($suffix),
1311 "ErrStr" => \$errstr,
1315 return ($fh, $path);
1324 Create a directory from a template. The template must end in
1325 X's that are replaced by the routine.
1327 $tmpdir_name = mkdtemp($template);
1329 Returns the name of the temporary directory created.
1330 Returns undef on failure.
1332 Directory must be removed by the caller.
1340 croak "Usage: mkdtemp(template)"
1343 my $template = shift;
1345 if ($^O eq 'VMS') { # dir names can end in delimiters
1346 $template =~ m/([\.\]:>]+)$/;
1347 $suffixlen = length($1);
1349 my ($junk, $tmpdir, $errstr);
1350 croak "Error creating temp directory from template $template\: $errstr"
1351 unless (($junk, $tmpdir) = _gettemp($template,
1354 "suffixlen" => $suffixlen,
1355 "ErrStr" => \$errstr,
1364 Returns a valid temporary filename but does not guarantee
1365 that the file will not be opened by someone else.
1367 $unopened_file = mktemp($template);
1369 Template is the same as that required by mkstemp().
1375 croak "Usage: mktemp(template)"
1378 my $template = shift;
1380 my ($tmpname, $junk, $errstr);
1381 croak "Error getting name to temp file from template $template: $errstr"
1382 unless (($junk, $tmpname) = _gettemp($template,
1386 "ErrStr" => \$errstr,
1394 =head1 POSIX FUNCTIONS
1396 This section describes the re-implementation of the tmpnam()
1397 and tmpfile() functions described in L<POSIX>
1398 using the mkstemp() from this module.
1400 Unlike the L<POSIX|POSIX> implementations, the directory used
1401 for the temporary file is not specified in a system include
1402 file (C<P_tmpdir>) but simply depends on the choice of tmpdir()
1403 returned by L<File::Spec|File::Spec>. On some implementations this
1404 location can be set using the C<TMPDIR> environment variable, which
1406 If this is a problem, simply use mkstemp() and specify a template.
1412 When called in scalar context, returns the full name (including path)
1413 of a temporary file (uses mktemp()). The only check is that the file does
1414 not already exist, but there is no guarantee that that condition will
1419 When called in list context, a filehandle to the open file and
1420 a filename are returned. This is achieved by calling mkstemp()
1421 after constructing a suitable template.
1423 ($fh, $file) = tmpnam();
1425 If possible, this form should be used to prevent possible
1428 See L<File::Spec/tmpdir> for information on the choice of temporary
1429 directory for a particular operating system.
1435 # Retrieve the temporary directory name
1436 my $tmpdir = File::Spec->tmpdir;
1438 croak "Error temporary directory is not writable"
1441 # Use a ten character template and append to tmpdir
1442 my $template = File::Spec->catfile($tmpdir, TEMPXXX);
1445 return mkstemp($template);
1447 return mktemp($template);
1454 In scalar context, returns the filehandle of a temporary file.
1458 The file is removed when the filehandle is closed or when the program
1459 exits. No access to the filename is provided.
1465 # Simply call tmpnam() in a list context
1466 my ($fh, $file) = tmpnam();
1468 # Make sure file is removed when filehandle is closed
1469 unlink0($fh, $file) or croak "Unable to unlink temporary file: $!";
1477 =head1 ADDITIONAL FUNCTIONS
1479 These functions are provided for backwards compatibility
1480 with common tempfile generation C library functions.
1482 They are not exported and must be addressed using the full package
1489 Return the name of a temporary file in the specified directory
1490 using a prefix. The file is guaranteed not to exist at the time
1491 the function was called, but such guarantees are good for one
1492 clock tick only. Always use the proper form of C<sysopen>
1493 with C<O_CREAT | O_EXCL> if you must open such a filename.
1495 $filename = File::Temp::tempnam( $dir, $prefix );
1497 Equivalent to running mktemp() with $dir/$prefixXXXXXXXX
1498 (using unix file convention as an example)
1500 Because this function uses mktemp(), it can suffer from race conditions.
1506 croak 'Usage tempnam($dir, $prefix)' unless scalar(@_) == 2;
1508 my ($dir, $prefix) = @_;
1510 # Add a string to the prefix
1511 $prefix .= 'XXXXXXXX';
1513 # Concatenate the directory to the file
1514 my $template = File::Spec->catfile($dir, $prefix);
1516 return mktemp($template);
1522 =head1 UTILITY FUNCTIONS
1524 Useful functions for dealing with the filehandle and filename.
1530 Given an open filehandle and the associated filename, make a safe
1531 unlink. This is achieved by first checking that the filename and
1532 filehandle initially point to the same file and that the number of
1533 links to the file is 1 (all fields returned by stat() are compared).
1534 Then the filename is unlinked and the filehandle checked once again to
1535 verify that the number of links on that file is now 0. This is the
1536 closest you can come to making sure that the filename unlinked was the
1537 same as the file whose descriptor you hold.
1539 unlink0($fh, $path) or die "Error unlinking file $path safely";
1541 Returns false on error. The filehandle is not closed since on some
1542 occasions this is not required.
1544 On some platforms, for example Windows NT, it is not possible to
1545 unlink an open file (the file must be closed first). On those
1546 platforms, the actual unlinking is deferred until the program ends and
1547 good status is returned. A check is still performed to make sure that
1548 the filehandle and filename are pointing to the same thing (but not at
1549 the time the end block is executed since the deferred removal may not
1550 have access to the filehandle).
1552 Additionally, on Windows NT not all the fields returned by stat() can
1553 be compared. For example, the C<dev> and C<rdev> fields seem to be
1554 different. Also, it seems that the size of the file returned by stat()
1555 does not always agree, with C<stat(FH)> being more accurate than
1556 C<stat(filename)>, presumably because of caching issues even when
1557 using autoflush (this is usually overcome by waiting a while after
1558 writing to the tempfile before attempting to C<unlink0> it).
1560 Finally, on NFS file systems the link count of the file handle does
1561 not always go to zero immediately after unlinking. Currently, this
1562 command is expected to fail on NFS disks.
1568 croak 'Usage: unlink0(filehandle, filename)'
1569 unless scalar(@_) == 2;
1572 my ($fh, $path) = @_;
1574 warn "Unlinking $path using unlink0\n"
1577 # Stat the filehandle
1580 if ($fh[3] > 1 && $^W) {
1581 carp "unlink0: fstat found too many links; SB=@fh" if $^W;
1585 my @path = stat $path;
1588 carp "unlink0: $path is gone already" if $^W;
1592 # this is no longer a file, but may be a directory, or worse
1594 confess "panic: $path is no longer a file: SB=@fh";
1597 # Do comparison of each member of the array
1598 # On WinNT dev and rdev seem to be different
1599 # depending on whether it is a file or a handle.
1600 # Cannot simply compare all members of the stat return
1601 # Select the ones we can use
1602 my @okstat = (0..$#fh); # Use all by default
1603 if ($^O eq 'MSWin32') {
1604 @okstat = (1,2,3,4,5,7,8,9,10);
1605 } elsif ($^O eq 'os2') {
1606 @okstat = (0, 2..$#fh);
1607 } elsif ($^O eq 'VMS') { # device and file ID are sufficient
1609 } elsif ($^O eq 'dos') {
1610 @okstat = (0,2..7,11..$#fh);
1613 # Now compare each entry explicitly by number
1615 print "Comparing: $_ : $fh[$_] and $path[$_]\n" if $DEBUG;
1616 # Use eq rather than == since rdev, blksize, and blocks (6, 11,
1617 # and 12) will be '' on platforms that do not support them. This
1618 # is fine since we are only comparing integers.
1619 unless ($fh[$_] eq $path[$_]) {
1620 warn "Did not match $_ element of stat\n" if $DEBUG;
1625 # attempt remove the file (does not work on some platforms)
1626 if (_can_unlink_opened_file()) {
1627 # XXX: do *not* call this on a directory; possible race
1628 # resulting in recursive removal
1629 croak "unlink0: $path has become a directory!" if -d $path;
1630 unlink($path) or return 0;
1632 # Stat the filehandle
1635 print "Link count = $fh[3] \n" if $DEBUG;
1637 # Make sure that the link count is zero
1638 # - Cygwin provides deferred unlinking, however,
1639 # on Win9x the link count remains 1
1640 return ( $fh[3] == 0 or $^O eq 'cygwin' ? 1 : 0);
1643 _deferred_unlink($fh, $path, 0);
1651 =head1 PACKAGE VARIABLES
1653 These functions control the global state of the package.
1659 Controls the lengths to which the module will go to check the safety of the
1660 temporary file or directory before proceeding.
1667 Do the basic security measures to ensure the directory exists and
1668 is writable, that the umask() is fixed before opening of the file,
1669 that temporary files are opened only if they do not already exist, and
1670 that possible race conditions are avoided. Finally the L<unlink0|"unlink0">
1671 function is used to remove files safely.
1675 In addition to the STANDARD security, the output directory is checked
1676 to make sure that it is owned either by root or the user running the
1677 program. If the directory is writable by group or by other, it is then
1678 checked to make sure that the sticky bit is set.
1680 Will not work on platforms that do not support the C<-k> test
1685 In addition to the MEDIUM security checks, also check for the
1686 possibility of ``chown() giveaway'' using the L<POSIX|POSIX>
1687 sysconf() function. If this is a possibility, each directory in the
1688 path is checked in turn for safeness, recursively walking back to the
1691 For platforms that do not support the L<POSIX|POSIX>
1692 C<_PC_CHOWN_RESTRICTED> symbol (for example, Windows NT) it is
1693 assumed that ``chown() giveaway'' is possible and the recursive test
1698 The level can be changed as follows:
1700 File::Temp->safe_level( File::Temp::HIGH );
1702 The level constants are not exported by the module.
1704 Currently, you must be running at least perl v5.6.0 in order to
1705 run with MEDIUM or HIGH security. This is simply because the
1706 safety tests use functions from L<Fcntl|Fcntl> that are not
1707 available in older versions of perl. The problem is that the version
1708 number for Fcntl is the same in perl 5.6.0 and in 5.005_03 even though
1709 they are different versions.
1711 On systems that do not support the HIGH or MEDIUM safety levels
1712 (for example Win NT or OS/2) any attempt to change the level will
1713 be ignored. The decision to ignore rather than raise an exception
1714 allows portable programs to be written with high security in mind
1715 for the systems that can support this without those programs failing
1716 on systems where the extra tests are irrelevant.
1718 If you really need to see whether the change has been accepted
1719 simply examine the return value of C<safe_level>.
1721 $newlevel = File::Temp->safe_level( File::Temp::HIGH );
1722 die "Could not change to high security"
1723 if $newlevel != File::Temp::HIGH;
1728 # protect from using the variable itself
1729 my $LEVEL = STANDARD;
1734 if (($level != STANDARD) && ($level != MEDIUM) && ($level != HIGH)) {
1735 carp "safe_level: Specified level ($level) not STANDARD, MEDIUM or HIGH - ignoring\n" if $^W;
1737 # Dont allow this on perl 5.005 or earlier
1738 if ($] < 5.006 && $level != STANDARD) {
1739 # Cant do MEDIUM or HIGH checks
1740 croak "Currently requires perl 5.006 or newer to do the safe checks";
1742 # Check that we are allowed to change level
1743 # Silently ignore if we can not.
1744 $LEVEL = $level if _can_do_level($level);
1753 This is the highest UID on the current system that refers to a root
1754 UID. This is used to make sure that the temporary directory is
1755 owned by a system UID (C<root>, C<bin>, C<sys> etc) rather than
1758 This is required since on many unix systems C</tmp> is not owned
1761 Default is to assume that any UID less than or equal to 10 is a root
1764 File::Temp->top_system_uid(10);
1765 my $topid = File::Temp->top_system_uid;
1767 This value can be adjusted to reduce security checking if required.
1768 The value is only relevant when C<safe_level> is set to MEDIUM or higher.
1775 my $TopSystemUID = 10;
1776 sub top_system_uid {
1780 croak "top_system_uid: UIDs should be numeric"
1781 unless $newuid =~ /^\d+$/s;
1782 $TopSystemUID = $newuid;
1784 return $TopSystemUID;
1790 For maximum security, endeavour always to avoid ever looking at,
1791 touching, or even imputing the existence of the filename. You do not
1792 know that that filename is connected to the same file as the handle
1793 you have, and attempts to check this can only trigger more race
1794 conditions. It's far more secure to use the filehandle alone and
1795 dispense with the filename altogether.
1797 If you need to pass the handle to something that expects a filename
1798 then, on a unix system, use C<"/dev/fd/" . fileno($fh)> for arbitrary
1799 programs, or more generally C<< "+<=&" . fileno($fh) >> for Perl
1800 programs. You will have to clear the close-on-exec bit on that file
1801 descriptor before passing it to another process.
1803 use Fcntl qw/F_SETFD F_GETFD/;
1804 fcntl($tmpfh, F_SETFD, 0)
1805 or die "Can't clear close-on-exec flag on temp fh: $!\n";
1807 =head2 Temporary files and NFS
1809 Some problems are associated with using temporary files that reside
1810 on NFS file systems and it is recommended that a local filesystem
1811 is used whenever possible. Some of the security tests will most probably
1812 fail when the temp file is not local. Additionally, be aware that
1813 the performance of I/O operations over NFS will not be as good as for
1818 Originally began life in May 1999 as an XS interface to the system
1819 mkstemp() function. In March 2000, the OpenBSD mkstemp() code was
1820 translated to Perl for total control of the code's
1821 security checking, to ensure the presence of the function regardless of
1822 operating system and to help with portability.
1826 L<POSIX/tmpnam>, L<POSIX/tmpfile>, L<File::Spec>, L<File::Path>
1828 See L<IO::File> and L<File::MkTemp> for different implementations of
1829 temporary file handling.
1833 Tim Jenness E<lt>t.jenness@jach.hawaii.eduE<gt>
1835 Copyright (C) 1999, 2000 Tim Jenness and the UK Particle Physics and
1836 Astronomy Research Council. All Rights Reserved. This program is free
1837 software; you can redistribute it and/or modify it under the same
1838 terms as Perl itself.
1840 Original Perl implementation loosely based on the OpenBSD C code for
1841 mkstemp(). Thanks to Tom Christiansen for suggesting that this module
1842 should be written and providing ideas for code improvements and
1843 security enhancements.