X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlport.pod;h=3b11a4f45eeebe8403908636098ee4db99a0e852;hb=ba370e9b8a212c313d985163053c7ed938fcae22;hp=0518478b239aeda99dc5de4c911d2c347b2138e4;hpb=055fd3a96a4b067d75446c3d47ffc318e9acc40d;p=p5sagit%2Fp5-mst-13.2.git diff --git a/pod/perlport.pod b/pod/perlport.pod index 0518478..3b11a4f 100644 --- a/pod/perlport.pod +++ b/pod/perlport.pod @@ -94,6 +94,26 @@ 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(/:/); + #... + } + +You can get away with this on Unix and MacOS (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 Dunce::Files module can +help audit your code for misuses of chop(). + +When dealing with binary files (or text files in binary mode) be sure +to explicitly set $/ to the appropriate value for your file format +before using chomp(). + Because of the "text" mode translation, DOSish perls have limitations in using C and C on a file accessed in "text" mode. Stick to C-ing to locations you got from C (and no @@ -181,10 +201,12 @@ numbers to secondary storage such as a disk file or tape. Conflicting storage orders make utter mess out of the numbers. If a little-endian host (Intel, VAX) stores 0x12345678 (305419896 in -decimal), a big-endian host (Motorola, MIPS, Sparc, PA) reads it as -0x78563412 (2018915346 in decimal). To avoid this problem in network -(socket) connections use the C and C formats C -and C, the "network" orders. These are guaranteed to be portable. +decimal), a big-endian host (Motorola, Sparc, PA) reads it as +0x78563412 (2018915346 in decimal). Alpha and MIPS can be either: +Digital/Compaq used/uses them in little-endian mode; SGI/Cray uses +them in big-endian mode. To avoid this problem in network (socket) +connections use the C and C formats C and C, the +"network" orders. These are guaranteed to be portable. You can explore the endianness of your platform by unpacking a data structure packed in native format such as: @@ -197,7 +219,7 @@ If you need to distinguish between endian architectures you could use either of the variables set like so: $is_big_endian = unpack("h*", pack("s", 1)) =~ /01/; - $is_litte_endian = unpack("h*", pack("s", 1)) =~ /^1/; + $is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/; Differing widths can cause truncation even between platforms of equal endianness. The platform of shorter width loses the upper parts of the @@ -207,8 +229,8 @@ transferring or storing raw binary numbers. One can circumnavigate both these problems in two ways. Either transfer and store numbers always in text format, instead of raw binary, or else consider using modules like Data::Dumper (included in -the standard distribution as of Perl 5.005) and Storable. Keeping -all data as text significantly simplifies matters. +the standard distribution as of Perl 5.005) and Storable (included as +of perl 5.8). Keeping all data as text significantly simplifies matters. =head2 Files and Filesystems @@ -217,7 +239,7 @@ So, it is reasonably safe to assume that all platforms support the notion of a "path" to uniquely identify a file on the system. How that path is really written, though, differs considerably. -Atlhough similar, file path specifications differ between Unix, +Although similar, file path specifications differ between Unix, Windows, S, OS/2, VMS, VOS, S, and probably others. Unix, for example, is one of the few OSes that has the elegant idea of a single root directory. @@ -330,9 +352,31 @@ file already tied or opened; C or C it first. Don't open the same file more than once at a time for writing, as some operating systems put mandatory locks on such files. +Don't assume that write/modify permission on a directory gives the +right to add or delete files/directories in that directory. That is +filesystem specific: in some filesystems you need write/modify +permission also (or even just) in the file/directory itself. In some +filesystems (AFS, DFS) the permission to add/delete directory entries +is a completely separate permission. + +Don't assume that a single C completely gets rid of the file: +some filesystems (most notably the ones in VMS) have versioned +filesystems, and unlink() removes only the most recent one (it doesn't +remove all the versions because by default the native tools on those +platforms remove just the most recent version, too). The portable +idiom to remove all the versions of a file is + + 1 while unlink "file"; + +This will terminate if the file is undeleteable for some reason +(protected, not there, and so on). + Don't count on a specific environment variable existing in C<%ENV>. Don't count on C<%ENV> entries being case-sensitive, or even -case-preserving. +case-preserving. Don't try to clear %ENV by saying C<%ENV = ();>, or, +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. Don't count on signals or C<%SIG> for anything. @@ -355,7 +399,7 @@ Commands that launch external processes are generally supported on most platforms (though many of them do not support any type of forking). The problem with using them arises from what you invoke them on. External tools are often named differently on different -platforms, may not be available in the same location, migth accept +platforms, may not be available in the same location, might accept different arguments, can behave differently, and often present their results in a platform-dependent way. Thus, you should seldom depend on them to produce consistent results. (Then again, if you're calling @@ -379,6 +423,14 @@ simple, platform-independent mailing. The Unix System V IPC (C) is not available even on all Unix platforms. +Do not use either the bare result of C or +bare v-strings (such as C) to represent IPv4 addresses: +both forms just pack the four bytes into network order. That this +would be equal to the C language C struct (which is what the +socket code internally uses) is not guaranteed. To be portable use +the routines of the Socket extension, such as C, +C, and C. + The rule of thumb for portable code is: Do it all in portable Perl, or use a module (that may internally implement it with platform-specific code, but expose a common interface). @@ -507,7 +559,7 @@ often happens when tests spawn off other processes or call external programs to aid in the testing, or when (as noted above) the tests assume certain things about the filesystem and paths. Be careful not to depend on a specific output style for errors, such as when -checking C<$!> after an system call. Some platforms expect a certain +checking C<$!> after a system call. Some platforms expect a certain output format, and perl on those platforms may have been adjusted accordingly. Most specifically, don't anchor a regex when testing an error value. @@ -528,7 +580,7 @@ a given module works on a given platform. =item Mailing list: cpan-testers@perl.org -=item Testing results: C +=item Testing results: http://testers.cpan.org/ =back @@ -570,7 +622,7 @@ are a few of the more popular Unix flavors: Linux linux ppc-linux HP-UX hpux PA-RISC1.1 IRIX irix irix - Mac OS X rhapsody rhapsody + Mac OS X darwin darwin MachTen PPC machten powerpc-machten NeXT 3 next next-fat NeXT 4 next OPENSTEP-Mach @@ -638,38 +690,73 @@ often assume nothing about their data. The C<$^O> variable and the C<$Config{archname}> values for various DOSish perls are as follows: - OS $^O $Config{'archname'} - -------------------------------------------- - MS-DOS dos - PC-DOS dos - OS/2 os2 - Windows 95 MSWin32 MSWin32-x86 - Windows 98 MSWin32 MSWin32-x86 - Windows NT MSWin32 MSWin32-x86 - Windows NT MSWin32 MSWin32-ALPHA - Windows NT MSWin32 MSWin32-ppc - Cygwin cygwin + OS $^O $Config{archname} ID Version + -------------------------------------------------------- + MS-DOS dos ? + PC-DOS dos ? + OS/2 os2 ? + Windows 3.1 ? ? 0 3 01 + Windows 95 MSWin32 MSWin32-x86 1 4 00 + Windows 98 MSWin32 MSWin32-x86 1 4 10 + Windows ME MSWin32 MSWin32-x86 1 ? + Windows NT MSWin32 MSWin32-x86 2 4 xx + Windows NT MSWin32 MSWin32-ALPHA 2 4 xx + Windows NT MSWin32 MSWin32-ppc 2 4 xx + Windows 2000 MSWin32 MSWin32-x86 2 5 xx + Windows XP MSWin32 MSWin32-x86 2 ? + Windows CE MSWin32 ? 3 + Cygwin cygwin ? + +The various MSWin32 Perl's can distinguish the OS they are running on +via the value of the fifth element of the list returned from +Win32::GetOSVersion(). For example: + + if ($^O eq 'MSWin32') { + my @os_version_info = Win32::GetOSVersion(); + print +('3.1','95','NT')[$os_version_info[4]],"\n"; + } Also see: =over 4 -=item The djgpp environment for DOS, C +=item * + +The djgpp environment for DOS, http://www.delorie.com/djgpp/ +and L. -=item The EMX environment for DOS, OS/2, etc. C, -C or -C +=item * -=item Build instructions for Win32, L. +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 The ActiveState Pages, C +=item * -=item The Cygwin environment for Win32; F (installed -as L), C +Build instructions for Win32 in L, or under the Cygnus environment +in L. -=item The U/WIN environment for Win32, -C +=item * +The C modules in L. + +=item * + +The ActiveState Pages, http://www.activestate.com/ + +=item * + +The Cygwin environment for Win32; F (installed +as L), http://www.cygwin.com/ + +=item * + +The U/WIN environment for Win32, +http://www.research.att.com/sw/tools/uwin/ + +=item * + +Build instructions for OS/2, L =back @@ -729,30 +816,32 @@ the application or MPW tool version is running, check: $is_ppc = $MacPerl::Architecture eq 'MacPPC'; $is_68k = $MacPerl::Architecture eq 'Mac68K'; -S and S, based on NeXT's OpenStep OS, will -(in theory) be able to run MacPerl natively, under the "Classic" -environment. The new "Cocoa" environment (formerly called the "Yellow Box") -may run a slightly modified version of MacPerl, using the Carbon interfaces. - -S and its Open Source version, Darwin, both run Unix -perl natively (with a few patches). Full support for these -is slated for perl 5.6. +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 The MacPerl Pages, C. +=item * + +MacPerl Development, http://dev.macperl.org/ . + +=item * + +The MacPerl Pages, http://www.macperl.com/ . -=item The MacPerl mailing lists, C. +=item * -=item MacPerl Module Porters, C. +The MacPerl mailing lists, http://lists.perl.org/ . =back =head2 VMS -Perl on VMS is discussed in F in the perl distribution. +Perl on VMS is discussed in L in the perl distribution. Perl on VMS can accept either VMS- or Unix-style file specifications as in either of the following: @@ -813,10 +902,11 @@ process on VMS, is a pure Perl module that can easily be installed on non-VMS platforms and can be helpful for conversions to and from RMS native formats. -What C<\n> represents depends on the type of file opened. It could -be C<\015>, C<\012>, C<\015\012>, or nothing. The VMS::Stdio module -provides access to the special fopen() requirements of files with unusual -attributes on VMS. +What C<\n> represents depends on the type of file opened. It usually +represents C<\012> but it could also be C<\015>, C<\012>, C<\015\012>, +C<\000>, C<\040>, or nothing depending on the file organiztion and +record format. The VMS::Stdio module provides access to the +special fopen() requirements of files with unusual attributes on VMS. TCP/IP stacks are optional on VMS, so socket routines might not be implemented. UDP sockets may not be supported. @@ -844,21 +934,27 @@ Also see: =over 4 -=item F (installed as L), L +=item * -=item vmsperl list, C +F (installed as L), L -Put the words C in message body. +=item * -=item vmsperl on the web, C +vmsperl list, majordomo@perl.org + +(Put the words C in message body.) + +=item * + +vmsperl on the web, http://www.sidhe.org/vmsperl/index.html =back =head2 VOS -Perl on VOS is discussed in F in the perl distribution. -Perl on VOS can accept either VOS- or Unix-style file -specifications as in either of the following: +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: $ perl -ne "print if /perl_setup/i" >system>notices $ perl -ne "print if /perl_setup/i" /system/notices @@ -874,16 +970,15 @@ 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. -The following C functions are unimplemented on VOS, and any attempt by -Perl to use them will result in a fatal error message and an immediate -exit from Perl: dup, do_aspawn, do_spawn, fork, waitpid. Once these -functions become available in the VOS POSIX.1 implementation, you can -either recompile and rebind Perl, or you can download a newer port from -ftp.stratus.com. +See F for restrictions that apply when Perl is built +with the alpha version of VOS POSIX.1 support. + +Perl on VOS is built without any extensions and does not support +dynamic loading. The value of C<$^O> on VOS is "VOS". To determine the architecture that you are running on without resorting to loading all of C<%Config> you -can examine the content of the C<@INC> array like so: +can examine the content of the @INC array like so: if ($^O =~ /VOS/) { print "I'm on a Stratus box!\n"; @@ -909,16 +1004,22 @@ Also see: =over 4 -=item F +=item * + +F + +=item * -=item VOS mailing list +The VOS mailing list. There is no specific mailing list for Perl on VOS. You can post comments to the comp.sys.stratus newsgroup, or subscribe to the general Stratus mailing list. Send a letter with "Subscribe Info-Stratus" in the message body to majordomo@list.stratagy.com. -=item VOS Perl on the web at C +=item * + +VOS Perl on the web at http://ftp.stratus.com/pub/vos/vos.html =back @@ -931,6 +1032,7 @@ Character Code Set ID 0037 for OS/400 and either 1047 or POSIX-BC for S/390 systems). On the mainframe perl currently works under the "Unix system services for OS/390" (formerly known as OpenEdition), VM/ESA OpenEdition, or the BS200 POSIX-BC system (BS2000 is supported in perl 5.6 and greater). +See L for details. As of R2.5 of USS for OS/390 and Version 2.3 of VM/ESA these Unix sub-systems do not support the C<#!> shebang trick for script invocation. @@ -999,15 +1101,23 @@ Also see: =over 4 -=item F, F, F +=item * + +* + +L, F, F, F, +L. -=item perl-mvs list +=item * The perl-mvs@perl.org list is for discussion of porting issues as well as general usage issues for all EBCDIC Perls. Send a message body of "subscribe perl-mvs" to majordomo@perl.org. -=item AS/400 Perl information at C +=item * + +AS/400 Perl information at +http://as400.rochester.ibm.com/ as well as on CPAN in the F directory. =back @@ -1138,23 +1248,33 @@ See also: =over 4 -=item Amiga, F (installed as L). +=item * + +Amiga, F (installed as L). + +=item * -=item Atari, F and Guido Flohr's web page -C +Atari, F and Guido Flohr's web page +http://stud.uni-sb.de/~gufl0000/ -=item Be OS, F +=item * -=item HP 300 MPE/iX, F and Mark Bixby's web page -C +Be OS, F -=item Novell Netware +=item * + +HP 300 MPE/iX, F and Mark Bixby's web page +http://www.bixby.org/mark/perlix.html + +=item * A free perl5-based PERL.NLM for Novell Netware is available in -precompiled binary and source code form from C +precompiled binary and source code form from http://www.novell.com/ as well as from CPAN. -=item Plan 9, F +=item * + +Plan 9, F =back @@ -1223,6 +1343,12 @@ suffixes. C<-S> is meaningless. (Win32) C<-x> (or C<-X>) determine if a file has an executable file type. (S) +=item alarm SECONDS + +=item alarm + +Not implemented. (Win32) + =item binmode FILEHANDLE Meaningless. (S, S) @@ -1290,6 +1416,17 @@ Implemented via Spawn. (VM/ESA) Does not automatically flush output handles on some platforms. (SunOS, Solaris, HP-UX) +=item exit EXPR + +=item exit + +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 +(C<1>); this mapping cannot be overridden. Any other argument to exit() +is used directly as Perl's exit status. (VMS) + =item fcntl FILEHANDLE,FUNCTION,SCALAR Not implemented. (Win32, VMS) @@ -1435,23 +1572,14 @@ Not implemented. (Plan9, Win32) =item getsockopt SOCKET,LEVEL,OPTNAME -Not implemented. (S, Plan9) +Not implemented. (Plan9) =item glob EXPR =item glob -Globbing built-in, but only C<*> and C metacharacters are supported. -(S) - -Features depend on external perlglob.exe or perlglob.bat. May be -overridden with something like File::DosGlob, which is recommended. -(Win32) - -Globbing built-in, but only C<*> and C metacharacters are supported. -Globbing relies on operating system calls, which may return filenames -in any order. As most filesystems are case-insensitive, even "sorted" -filenames will not be in case-sensitive order. (S) +This operator is implemented via the File::Glob extension on most +platforms. See L for portability information. =item ioctl FILEHANDLE,FUNCTION,SCALAR @@ -1464,12 +1592,17 @@ Available only for socket handles. (S) =item kill SIGNAL, LIST -Not implemented, hence not useful for taint checking. (S, -S) +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 makes the process 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 doesn't have the semantics of C, i.e. it doesn't send +a signal to the identified process like it does on Unix platforms. +Instead C terminates the process identified by $pid, +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) =item link OLDFILE,NEWFILE @@ -1489,7 +1622,7 @@ under NTFS only. Not implemented. (VMS, S) -Return values may be bogus. (Win32) +Return values (especially for device and inode) may be bogus. (Win32) =item msgctl ID,CMD,ARG @@ -1515,8 +1648,6 @@ platforms. (SunOS, Solaris, HP-UX) =item pipe READHANDLE,WRITEHANDLE -Not implemented. (S) - Very limited functionality. (MiNT) =item readlink EXPR @@ -1527,10 +1658,12 @@ Not implemented. (Win32, VMS, S) =item select RBITS,WBITS,EBITS,TIMEOUT -Only implemented on sockets. (Win32) +Only implemented on sockets. (Win32, VMS) Only reliable on sockets. (S) +Note that the C