X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlport.pod;h=87b2b27406cd87c27adabb1196bd15949b2f5246;hb=45b194c55901890d782546bf70eee5b9b5451083;hp=de753e7844b212e3daa7446bee380d9502e0c317;hpb=84d78eb7303a2024a7c31dbf1ef17c1815e84d3c;p=p5sagit%2Fp5-mst-13.2.git diff --git a/pod/perlport.pod b/pod/perlport.pod index de753e7..87b2b27 100644 --- a/pod/perlport.pod +++ b/pod/perlport.pod @@ -59,7 +59,7 @@ choices you can avail yourself of, and at the same time you can give your users lots of platform choices. On the other hand, when you have to take advantage of some unique feature of a particular platform, as is often the case with systems programming (whether for Unix, Windows, -S, VMS, etc.), consider writing platform-specific code. +VMS, etc.), consider writing platform-specific code. When the code will run on only two or three operating systems, you may need to consider only the differences of those particular systems. @@ -88,27 +88,15 @@ and S uses C<\015>. Perl uses C<\n> to represent the "logical" newline, where what is logical may depend on the platform in use. In MacPerl, C<\n> always -means C<\015>. In DOSish perls, C<\n> usually means C<\012>, but -when accessing a file in "text" mode, STDIO translates it to (or -from) C<\015\012>, depending on whether you're reading or writing. -Unix does the same thing on ttys in canonical mode. C<\015\012> -is commonly referred to as CRLF. - -A common cause of unportable programs is the misuse of chop() to trim -newlines: - - # XXX UNPORTABLE! - while() { - chop; - @array = split(/:/); - #... - } +means C<\015>. In DOSish perls, C<\n> usually means C<\012>, but when +accessing a file in "text" mode, perl uses the C<:crlf> layer that +translates it to (or from) C<\015\012>, depending on whether you're +reading or writing. Unix does the same thing on ttys in canonical +mode. C<\015\012> is commonly referred to as CRLF. -You can get away with this on Unix and Mac OS (they have a single -character end-of-line), but the same program will break under DOSish -perls because you're only chop()ing half the end-of-line. Instead, -chomp() should be used to trim newlines. The L module -can help audit your code for misuses of chop(). +To trim trailing newlines from text lines use chomp(). With default +settings that function looks for a trailing C<\n> character and thus +trims in a portable way. When dealing with binary files (or text files in binary mode) be sure to explicitly set $/ to the appropriate value for your file format @@ -272,7 +260,7 @@ as path separator, or in their own idiosyncratic ways (such as having several root directories and various "unrooted" device files such NIL: and LPT:). -S uses C<:> as a path separator instead of C. +S 9 and earlier used C<:> as a path separator instead of C. The filesystem may support neither hard links (C) nor symbolic links (C, C, C). @@ -283,7 +271,7 @@ modification timestamp), or one second granularity of any timestamps (e.g. the FAT filesystem limits the time granularity to two seconds). The "inode change timestamp" (the C<-C> filetest) may really be the -"creation timestamp" (which it is not in UNIX). +"creation timestamp" (which it is not in Unix). VOS perl can emulate Unix filenames with C as path separator. The native pathname characters greater-than, less-than, number-sign, and @@ -293,10 +281,10 @@ S perl can emulate Unix filenames with C as path separator, or go native and use C<.> for path separator and C<:> to signal filesystems and disk names. -Don't assume UNIX filesystem access semantics: that read, write, +Don't assume Unix filesystem access semantics: that read, write, and execute are all the permissions there are, and even if they exist, that their semantics (for example what do r, w, and x mean on -a directory) are the UNIX ones. The various UNIX/POSIX compatibility +a directory) are the Unix ones. The various Unix/POSIX compatibility layers usually try to make interfaces like chmod() work, but sometimes there simply is no good mapping. @@ -307,9 +295,9 @@ to be running the program. use File::Spec::Functions; chdir(updir()); # go up one directory - $file = catfile(curdir(), 'temp', 'file.txt'); + my $file = catfile(curdir(), 'temp', 'file.txt'); # on Unix and Win32, './temp/file.txt' - # on Mac OS, ':temp:file.txt' + # on Mac OS Classic, ':temp:file.txt' # on VMS, '[.temp]file.txt' File::Spec is available in the standard distribution as of version @@ -368,7 +356,7 @@ Always use C<< < >> explicitly to open a file for reading, or even better, use the three-arg version of open, unless you want the user to be able to specify a pipe open. - open(FILE, '<', $existing_file) or die $!; + open my $fh, '<', $existing_file) or die $!; If filenames might use strange characters, it is safest to open it with C instead of C. C is magic and can @@ -445,6 +433,16 @@ if you really have to, make it conditional on C<$^O ne 'VMS'> since in VMS the C<%ENV> table is much more than a per-process key-value string table. +On VMS, some entries in the %ENV hash are dynamically created when +their key is used on a read if they did not previously exist. The +values for C<$ENV{HOME}>, C<$ENV{TERM}>, C<$ENV{HOME}>, and C<$ENV{USER}>, +are known to be dynamically generated. The specific names that are +dynamically generated may vary with the version of the C library on VMS, +and more may exist than is documented. + +On VMS by default, changes to the %ENV hash are persistent after the process +exits. This can cause unintended issues. + Don't count on signals or C<%SIG> for anything. Don't count on filename globbing. Use C, C, and @@ -454,7 +452,7 @@ Don't count on per-program environment variables, or per-program current directories. Don't count on specific values of C<$!>, neither numeric nor -especially the strings values-- users may switch their locales causing +especially the strings values. Users may switch their locales causing error messages to be translated into their languages. If you can trust a POSIXish environment, you can portably use the symbols defined by the Errno module, like ENOENT. And don't trust on the values of C<$!> @@ -483,14 +481,14 @@ To convert $^X to a file pathname, taking account of the requirements of the various operating system possibilities, say: use Config; - $thisperl = $^X; + my $thisperl = $^X; if ($^O ne 'VMS') {$thisperl .= $Config{_exe} unless $thisperl =~ m/$Config{_exe}$/i;} To convert $Config{perlpath} to a file pathname, say: use Config; - $thisperl = $Config{perlpath}; + my $thisperl = $Config{perlpath}; if ($^O ne 'VMS') {$thisperl .= $Config{_exe} unless $thisperl =~ m/$Config{_exe}$/i;} @@ -520,13 +518,13 @@ Don't assume that you can ping hosts and get replies. Don't assume that any particular port (service) will respond. -Don't assume that Sys::Hostname (or any other API or command) -returns either a fully qualified hostname or a non-qualified hostname: -it all depends on how the system had been configured. Also remember -things like DHCP and NAT-- the hostname you get back might not be very -useful. +Don't assume that Sys::Hostname (or any other API or command) returns +either a fully qualified hostname or a non-qualified hostname: it all +depends on how the system had been configured. Also remember that for +things such as DHCP and NAT, the hostname you get back might not be +very useful. -All the above "don't":s may look daunting, and they are -- but the key +All the above "don't":s may look daunting, and they are, but the key is to degrade gracefully if one cannot reach the particular network service one wants. Croaking or hanging do not look very professional. @@ -637,14 +635,11 @@ When calculating specific times, such as for tests in time or date modules, it may be appropriate to calculate an offset for the epoch. require Time::Local; - $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70); + my $offset = Time::Local::timegm(0, 0, 0, 1, 0, 70); -The value for C<$offset> in Unix will be C<0>, but in Mac OS will be -some large number. C<$offset> can then be added to a Unix time value -to get what should be the proper value on any system. - -On Windows (at least), you shouldn't pass a negative value to C or -C. +The value for C<$offset> in Unix will be C<0>, but in Mac OS Classic +will be some large number. C<$offset> can then be added to a Unix time +value to get what should be the proper value on any system. =head2 Character sets and character encoding @@ -684,12 +679,9 @@ ISO 8859-1 bytes beyond 0x7f into your strings might cause trouble later. If the bytes are native 8-bit bytes, you can use the C pragma. If the bytes are in a string (regular expression being a curious string), you can often also use the C<\xHH> notation instead -of embedding the bytes as-is. If they are in some particular legacy -encoding (ether single-byte or something more complicated), you can -use the C pragma. (If you want to write your code in UTF-8, -you can use either the C pragma, or the C pragma.) -The C and C pragmata are available since Perl 5.6.0, and -the C pragma since Perl 5.8.0. +of embedding the bytes as-is. (If you want to write your code in UTF-8, +you can use the C.) The C and C pragmata are +available since Perl 5.6.0. =head2 System Resources @@ -701,10 +693,10 @@ of avoiding wasteful constructs such as: for (0..10000000) {} # bad for (my $x = 0; $x <= 10000000; ++$x) {} # good - @lines = ; # bad + my @lines = <$very_large_file>; # bad - while () {$file .= $_} # sometimes bad - $file = join('', ); # better + while (<$fh>) {$file .= $_} # sometimes bad + my $file = join('', <$fh>); # better The last two constructs may appear unintuitive to most people. The first repeatedly grows a string, whereas the second allocates a @@ -714,26 +706,26 @@ more efficient that the first. =head2 Security Most multi-user platforms provide basic levels of security, usually -implemented at the filesystem level. Some, however, do -not-- unfortunately. Thus the notion of user id, or "home" directory, +implemented at the filesystem level. Some, however, unfortunately do +not. Thus the notion of user id, or "home" directory, or even the state of being logged-in, may be unrecognizable on many platforms. If you write programs that are security-conscious, it is usually best to know what type of system you will be running under so that you can write code explicitly for that platform (or class of platforms). -Don't assume the UNIX filesystem access semantics: the operating +Don't assume the Unix filesystem access semantics: the operating system or the filesystem may be using some ACL systems, which are richer languages than the usual rwx. Even if the rwx exist, their semantics might be different. (From security viewpoint testing for permissions before attempting to do something is silly anyway: if one tries this, there is potential -for race conditions-- someone or something might change the +for race conditions. Someone or something might change the permissions between the permissions check and the actual operation. Just try the operation.) -Don't assume the UNIX user and group semantics: especially, don't +Don't assume the Unix user and group semantics: especially, don't expect the C<< $< >> and C<< $> >> (or the C<$(> and C<$)>) to work for switching identities (or memberships). @@ -820,6 +812,7 @@ are a few of the more popular Unix flavors: dgux dgux AViiON-dgux DYNIX/ptx dynixptx i386-dynixptx FreeBSD freebsd freebsd-i386 + Haiku haiku BePC-haiku Linux linux arm-linux Linux linux i386-linux Linux linux i586-linux @@ -827,7 +820,6 @@ are a few of the more popular Unix flavors: HP-UX hpux PA-RISC1.1 IRIX irix irix Mac OS X darwin darwin - MachTen PPC machten powerpc-machten NeXT 3 next next-fat NeXT 4 next OPENSTEP-Mach openbsd openbsd i386-openbsd @@ -854,10 +846,10 @@ Users familiar with I or I style shells should be aware that each of these file specifications may have subtle differences: - $filespec0 = "c:/foo/bar/file.txt"; - $filespec1 = "c:\\foo\\bar\\file.txt"; - $filespec2 = 'c:\foo\bar\file.txt'; - $filespec3 = 'c:\\foo\\bar\\file.txt'; + my $filespec0 = "c:/foo/bar/file.txt"; + my $filespec1 = "c:\\foo\\bar\\file.txt"; + my $filespec2 = 'c:\foo\bar\file.txt'; + my $filespec3 = 'c:\\foo\\bar\\file.txt'; System calls accept either C or C<\> as the path separator. However, many command-line utilities of DOS vintage treat C as @@ -940,7 +932,6 @@ and L. =item * The EMX environment for DOS, OS/2, etc. emx@iaehv.nl, -http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html or ftp://hobbes.nmsu.edu/pub/os2/dev/emx/ Also L. =item * @@ -972,89 +963,6 @@ Build instructions for OS/2, L =back -=head2 S - -Any module requiring XS compilation is right out for most people, because -MacPerl is built using non-free (and non-cheap!) compilers. Some XS -modules that can work with MacPerl are built and distributed in binary -form on CPAN. - -Directories are specified as: - - volume:folder:file for absolute pathnames - volume:folder: for absolute pathnames - :folder:file for relative pathnames - :folder: for relative pathnames - :file for relative pathnames - file for relative pathnames - -Files are stored in the directory in alphabetical order. Filenames are -limited to 31 characters, and may include any character except for -null and C<:>, which is reserved as the path separator. - -Instead of C, see C and C in the -Mac::Files module, or C and C. - -In the MacPerl application, you can't run a program from the command line; -programs that expect C<@ARGV> to be populated can be edited with something -like the following, which brings up a dialog box asking for the command -line arguments. - - if (!@ARGV) { - @ARGV = split /\s+/, MacPerl::Ask('Arguments?'); - } - -A MacPerl script saved as a "droplet" will populate C<@ARGV> with the full -pathnames of the files dropped onto the script. - -Mac users can run programs under a type of command line interface -under MPW (Macintosh Programmer's Workshop, a free development -environment from Apple). MacPerl was first introduced as an MPW -tool, and MPW can be used like a shell: - - perl myscript.plx some arguments - -ToolServer is another app from Apple that provides access to MPW tools -from MPW and the MacPerl app, which allows MacPerl programs to use -C, backticks, and piped C. - -"S" is the proper name for the operating system, but the value -in C<$^O> is "MacOS". To determine architecture, version, or whether -the application or MPW tool version is running, check: - - $is_app = $MacPerl::Version =~ /App/; - $is_tool = $MacPerl::Version =~ /MPW/; - ($version) = $MacPerl::Version =~ /^(\S+)/; - $is_ppc = $MacPerl::Architecture eq 'MacPPC'; - $is_68k = $MacPerl::Architecture eq 'Mac68K'; - -S, based on NeXT's OpenStep OS, runs MacPerl natively, under the -"Classic" environment. There is no "Carbon" version of MacPerl to run -under the primary Mac OS X environment. S and its Open Source -version, Darwin, both run Unix perl natively. - -Also see: - -=over 4 - -=item * - -MacPerl Development, http://dev.macperl.org/ . - -=item * - -The MacPerl Pages, http://www.macperl.com/ . - -=item * - -The MacPerl mailing lists, http://lists.perl.org/ . - -=item * - -MPW, ftp://ftp.apple.com/developer/Tool_Chest/Core_Mac_OS_Tools/ - -=back - =head2 VMS Perl on VMS is discussed in L in the perl distribution. @@ -1112,7 +1020,7 @@ Unicode characters. Characters that could be misinterpreted by the DCL shell or file parsing utilities need to be prefixed with the C<^> character, or replaced with hexadecimal characters prefixed with the C<^> character. Such prefixing is only needed with the pathnames are -in VMS format in applications. Programs that can accept the UNIX format +in VMS format in applications. Programs that can accept the Unix format of pathnames do not need the escape characters. The maximum length for filenames is 255 characters. The ODS-5 file system can handle both a case preserved and a case sensitive mode. @@ -1123,34 +1031,34 @@ Support for the extended file specifications is being done as optional settings to preserve backward compatibility with Perl scripts that assume the previous VMS limitations. -In general routines on VMS that get a UNIX format file specification -should return it in a UNIX format, and when they get a VMS format +In general routines on VMS that get a Unix format file specification +should return it in a Unix format, and when they get a VMS format specification they should return a VMS format unless they are documented to do a conversion. For routines that generate return a file specification, VMS allows setting if the C library which Perl is built on if it will be returned in VMS -format or in UNIX format. +format or in Unix format. With the ODS-2 file system, there is not much difference in syntax of -filenames without paths for VMS or UNIX. With the extended character +filenames without paths for VMS or Unix. With the extended character set available with ODS-5 there can be a significant difference. Because of this, existing Perl scripts written for VMS were sometimes -treating VMS and UNIX filenames interchangeably. Without the extended +treating VMS and Unix filenames interchangeably. Without the extended character set enabled, this behavior will mostly be maintained for backwards compatibility. When extended characters are enabled with ODS-5, the handling of -UNIX formatted file specifications is to that of a UNIX system. +Unix formatted file specifications is to that of a Unix system. VMS file specifications without extensions have a trailing dot. An -equivalent UNIX file specification should not show the trailing dot. +equivalent Unix file specification should not show the trailing dot. The result of all of this, is that for VMS, for portable scripts, you can not depend on Perl to present the filenames in lowercase, to be case sensitive, and that the filenames could be returned in either -UNIX or VMS format. +Unix or VMS format. And if a routine returns a file specification, unless it is intended to convert it, it should return it in the same format as it found it. @@ -1165,17 +1073,24 @@ return F when VMS is (though that file could be opened with C). With support for extended file specifications and if C was -given a UNIX format directory, a file named F will return F +given a Unix format directory, a file named F will return F and optionally in the exact case on the disk. When C is given a VMS format directory, then C should return F, and again with the optionally the exact case. RMS had an eight level limit on directory depths from any rooted logical -(allowing 16 levels overall) prior to VMS 7.2. Hence -C is a valid directory specification but -C is not. F authors might -have to take this into account, but at least they can refer to the former -as C. +(allowing 16 levels overall) prior to VMS 7.2, and even with versions of +VMS on VAX up through 7.3. Hence C is a +valid directory specification but C is +not. F authors might have to take this into account, but at +least they can refer to the former as C. + +Pumpkings and module integrators can easily see whether files with too many +directory levels have snuck into the core by running the following in the +top-level source directory: + + $ perl -ne "$_=~s/\s+.*//; print if scalar(split /\//) > 8;" < MANIFEST + The VMS::Filespec module, which gets installed as part of the build process on VMS, is a pure Perl module that can easily be installed on @@ -1231,9 +1146,7 @@ F (installed as L), L =item * -vmsperl list, majordomo@perl.org - -(Put the words C in message body.) +vmsperl list, vmsperl-subscribe@perl.org =item * @@ -1247,19 +1160,20 @@ Perl on VOS is discussed in F in the perl distribution (installed as L). Perl on VOS can accept either VOS- or Unix-style file specifications as in either of the following: - C<< $ perl -ne "print if /perl_setup/i" >system>notices >> - C<< $ perl -ne "print if /perl_setup/i" /system/notices >> + $ perl -ne "print if /perl_setup/i" >system>notices + $ perl -ne "print if /perl_setup/i" /system/notices or even a mixture of both as in: - C<< $ perl -ne "print if /perl_setup/i" >system/notices >> + $ perl -ne "print if /perl_setup/i" >system/notices Even though VOS allows the slash character to appear in object names, because the VOS port of Perl interprets it as a pathname delimiting character, VOS files, directories, or links whose names contain a slash character cannot be processed. Such files must be renamed before they can be processed by Perl. Note that VOS limits -file names to 32 or fewer characters. +file names to 32 or fewer characters, file names cannot start with a +C<-> character, or contain any character matching C<< tr/ !%&'()*+;<>?// >> The value of C<$^O> on VOS is "VOS". To determine the architecture that you are running on without resorting to loading all of C<%Config> you @@ -1500,13 +1414,13 @@ in C<$^O> is "riscos" (because we don't like shouting). =head2 Other perls Perl has been ported to many platforms that do not fit into any of -the categories listed above. Some, such as AmigaOS, Atari MiNT, -BeOS, HP MPE/iX, QNX, Plan 9, and VOS, have been well-integrated -into the standard Perl source code kit. You may need to see the -F directory on CPAN for information, and possibly binaries, -for the likes of: aos, Atari ST, lynxos, riscos, Novell Netware, -Tandem Guardian, I (Yes, we know that some of these OSes may -fall under the Unix category, but we are not a standards body.) +the categories listed above. Some, such as AmigaOS, BeOS, HP MPE/iX, +QNX, Plan 9, and VOS, have been well-integrated into the standard +Perl source code kit. You may need to see the F directory +on CPAN for information, and possibly binaries, for the likes of: +aos, Atari ST, lynxos, riscos, Novell Netware, Tandem Guardian, +I (Yes, we know that some of these OSes may fall under the +Unix category, but we are not a standards body.) Some approximate operating system names and their C<$^O> values in the "OTHER" category include: @@ -1527,17 +1441,12 @@ Amiga, F (installed as L). =item * -Atari, F and Guido Flohr's web page -http://stud.uni-sb.de/~gufl0000/ - -=item * - Be OS, F =item * HP 300 MPE/iX, F and Mark Bixby's web page -http://www.bixby.org/mark/perlix.html +http://www.bixby.org/mark/porting.html =item * @@ -1576,36 +1485,29 @@ L for a full description of available variables. =item -X -C<-r>, C<-w>, and C<-x> have a limited meaning only; directories -and applications are executable, and there are no uid/gid -considerations. C<-o> is not supported. (S) +C<-w> only inspects the read-only file attribute (FILE_ATTRIBUTE_READONLY), +which determines whether the directory can be deleted, not whether it can +be written to. Directories always have read and write access unless denied +by discretionary access control lists (DACLs). (S) C<-r>, C<-w>, C<-x>, and C<-o> tell whether the file is accessible, which may not reflect UIC-based file protections. (VMS) -C<-s> returns the size of the data fork, not the total size of data fork -plus resource fork. (S). - C<-s> by name on an open file will return the space reserved on disk, rather than the current extent. C<-s> on an open filehandle returns the current size. (S) C<-R>, C<-W>, C<-X>, C<-O> are indistinguishable from C<-r>, C<-w>, -C<-x>, C<-o>. (S, Win32, VMS, S) - -C<-b>, C<-c>, C<-k>, C<-g>, C<-p>, C<-u>, C<-A> are not implemented. -(S) +C<-x>, C<-o>. (Win32, VMS, S) -C<-g>, C<-k>, C<-l>, C<-p>, C<-u>, C<-A> are not particularly meaningful. +C<-g>, C<-k>, C<-l>, C<-u>, C<-A> are not particularly meaningful. (Win32, VMS, S) +C<-p> is not particularly meaningful. (VMS, S) + C<-d> is true if passed a device spec without an explicit directory. (VMS) -C<-T> and C<-B> are implemented, but might misclassify Mac text files -with foreign characters; this is the case will all platforms, but may -affect S often. (S) - C<-x> (or C<-X>) determine if a file ends in one of the executable suffixes. C<-S> is meaningless. (Win32) @@ -1625,7 +1527,7 @@ L. =item binmode -Meaningless. (S, S) +Meaningless. (S) Reopens file and restores pointer; if function fails, underlying filehandle may be closed, or pointer may be in a different position. @@ -1636,9 +1538,6 @@ the filehandle may be flushed. (Win32) =item chmod -Only limited meaning. Disabling/enabling write permission is mapped to -locking/unlocking the file. (S) - Only good for changing "owner" read-write access, "group", and "other" bits are meaningless. (Win32) @@ -1651,7 +1550,7 @@ in the SYSTEM environment settings. (Cygwin) =item chown -Not implemented. (S, Win32, S, S) +Not implemented. (Win32, S, S) Does nothing, but won't fail. (Win32) @@ -1659,7 +1558,7 @@ A little funky, because VOS's notion of ownership is a little funky (VOS). =item chroot -Not implemented. (S, Win32, VMS, S, S, VOS, VM/ESA) +Not implemented. (Win32, VMS, S, S, VOS, VM/ESA) =item crypt @@ -1676,7 +1575,7 @@ Not implemented. (VMS, S, VOS) =item dump -Not useful. (S, S) +Not useful. (S) Not supported. (Cygwin, Win32) @@ -1684,8 +1583,6 @@ Invokes VMS debugger. (VMS) =item exec -Not implemented. (S) - Implemented via Spawn. (VM/ESA) Does not automatically flush output handles on some platforms. @@ -1693,7 +1590,7 @@ Does not automatically flush output handles on some platforms. =item exit -Emulates UNIX exit() (which considers C to indicate an error) by +Emulates Unix exit() (which considers C to indicate an error) by mapping the C<1> to SS$_ABORT (C<44>). This behavior may be overridden with the pragma C. As with the CRTL's exit() function, C is also mapped to an exit status of SS$_NORMAL @@ -1712,13 +1609,13 @@ Some functions available based on the version of VMS. (VMS) =item flock -Not implemented (S, VMS, S, VOS). +Not implemented (VMS, S, VOS). Available only on Windows NT (not on Windows 95). (Win32) =item fork -Not implemented. (S, AmigaOS, S, VM/ESA, VMS) +Not implemented. (AmigaOS, S, VM/ESA, VMS) Emulated using multiple interpreters. See L. (Win32) @@ -1727,80 +1624,76 @@ Does not automatically flush output handles on some platforms. =item getlogin -Not implemented. (S, S) +Not implemented. (S) =item getpgrp -Not implemented. (S, Win32, VMS, S) +Not implemented. (Win32, VMS, S) =item getppid -Not implemented. (S, Win32, S) +Not implemented. (Win32, S) =item getpriority -Not implemented. (S, Win32, VMS, S, VOS, VM/ESA) +Not implemented. (Win32, VMS, S, VOS, VM/ESA) =item getpwnam -Not implemented. (S, Win32) +Not implemented. (Win32) Not useful. (S) =item getgrnam -Not implemented. (S, Win32, VMS, S) +Not implemented. (Win32, VMS, S) =item getnetbyname -Not implemented. (S, Win32, S) +Not implemented. (Win32, S) =item getpwuid -Not implemented. (S, Win32) +Not implemented. (Win32) Not useful. (S) =item getgrgid -Not implemented. (S, Win32, VMS, S) +Not implemented. (Win32, VMS, S) =item getnetbyaddr -Not implemented. (S, Win32, S) +Not implemented. (Win32, S) =item getprotobynumber -Not implemented. (S) - =item getservbyport -Not implemented. (S) - =item getpwent -Not implemented. (S, Win32, VM/ESA) +Not implemented. (Win32, VM/ESA) =item getgrent -Not implemented. (S, Win32, VMS, VM/ESA) +Not implemented. (Win32, VMS, VM/ESA) =item gethostbyname C does not work everywhere: you may have -to use C. (S, S) +to use C. (S) =item gethostent -Not implemented. (S, Win32) +Not implemented. (Win32) =item getnetent -Not implemented. (S, Win32, S) +Not implemented. (Win32, S) =item getprotoent -Not implemented. (S, Win32, S) +Not implemented. (Win32, S) =item getservent @@ -1808,15 +1701,15 @@ Not implemented. (Win32, S) =item sethostent -Not implemented. (S, Win32, S, S) +Not implemented. (Win32, S, S) =item setnetent -Not implemented. (S, Win32, S, S) +Not implemented. (Win32, S, S) =item setprotoent -Not implemented. (S, Win32, S, S) +Not implemented. (Win32, S, S) =item setservent @@ -1824,23 +1717,23 @@ Not implemented. (S, Win32, S) =item endpwent -Not implemented. (S, MPE/iX, VM/ESA, Win32) +Not implemented. (MPE/iX, VM/ESA, Win32) =item endgrent -Not implemented. (S, MPE/iX, S, VM/ESA, VMS, Win32) +Not implemented. (MPE/iX, S, VM/ESA, VMS, Win32) =item endhostent -Not implemented. (S, Win32) +Not implemented. (Win32) =item endnetent -Not implemented. (S, Win32, S) +Not implemented. (Win32, S) =item endprotoent -Not implemented. (S, Win32, S) +Not implemented. (Win32, S) =item endservent @@ -1857,7 +1750,10 @@ platforms. See L for portability information. =item gmtime -Same portability caveats as L. +In theory, gmtime() is reliable from -2**63 to 2**63-1. However, +because work arounds in the implementation use floating point numbers, +it will become inaccurate as the time gets larger. This is a bug and +will be fixed in the future. =item ioctl FILEHANDLE,FUNCTION,SCALAR @@ -1870,9 +1766,6 @@ Available only for socket handles. (S) =item kill -C is implemented for the sake of taint checking; -use with other signals is unimplemented. (S) - Not implemented, hence not useful for taint checking. (S) C doesn't have the semantics of C, i.e. it doesn't send @@ -1882,27 +1775,35 @@ and makes it exit immediately with exit status $sig. As in Unix, if $sig is 0 and the specified process exists, it returns true without actually terminating it. (Win32) +C will terminate the process specified by $pid and +recursively all child processes owned by it. This is different from +the Unix semantics, where the signal will be delivered to all +processes in the same process group as the process specified by +$pid. (Win32) + Is not supported for process identification number of 0 or negative numbers. (VMS) =item link -Not implemented. (S, MPE/iX, S) +Not implemented. (MPE/iX, S) Link count not updated because hard links are not quite that hard (They are sort of half-way between hard and soft links). (AmigaOS) -Hard links are implemented on Win32 (Windows NT and Windows 2000) -under NTFS only. +Hard links are implemented on Win32 under NTFS only. They are +natively supported on Windows 2000 and later. On Windows NT they +are implemented using the Windows POSIX subsystem support and the +Perl process will need Administrator or Backup Operator privileges +to create hard links. Available on 64 bit OpenVMS 8.2 and later. (VMS) =item localtime -Because Perl currently relies on the native standard C localtime() -function, it is only safe to use times between 0 and (2**31)-1. Times -outside this range may result in unexpected behavior depending on your -operating system's implementation of localtime(). +localtime() has the same range as L, but because time zone +rules change its accuracy for historical and future times may degrade +but usually by no more than an hour. =item lstat @@ -1918,22 +1819,15 @@ Return values (especially for device and inode) may be bogus. (Win32) =item msgrcv -Not implemented. (S, Win32, VMS, S, S, VOS) +Not implemented. (Win32, VMS, S, S, VOS) =item open -The C<|> variants are supported only if ToolServer is installed. -(S) - -open to C<|-> and C<-|> are unsupported. (S, Win32, S) +open to C<|-> and C<-|> are unsupported. (Win32, S) Opening a process does not automatically flush output handles on some platforms. (SunOS, Solaris, HP-UX) -=item pipe - -Very limited functionality. (MiNT) - =item readlink Not implemented. (Win32, VMS, S) @@ -1956,23 +1850,23 @@ Note that the C