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PERLCYGWIN(1pm)        Perl Programmers Reference Guide        PERLCYGWIN(1pm)


       perlcygwin - Perl for Cygwin


       This document will help you configure, make, test and install Perl on
       Cygwin.  This document also describes features of Cygwin that will
       affect how Perl behaves at runtime.

       NOTE: There are pre-built Perl packages available for Cygwin and a
       version of Perl is provided in the normal Cygwin install.  If you do
       not need to customize the configuration, consider using one of those


   Cygwin = GNU+Cygnus+Windows (Don't leave UNIX without it)
       The Cygwin tools are ports of the popular GNU development tools for
       Win32 platforms.  They run thanks to the Cygwin library which provides
       the UNIX system calls and environment these programs expect.  More
       information about this project can be found at:


       A recent net or commercial release of Cygwin is required.

       At the time this document was last updated, Cygwin 1.7.16 was current.

   Cygwin Configuration
       While building Perl some changes may be necessary to your Cygwin setup
       so that Perl builds cleanly.  These changes are not required for normal
       Perl usage.

       NOTE: The binaries that are built will run on all Win32 versions.  They
       do not depend on your host system (WinXP/Win2K/Win7) or your Cygwin
       configuration (binary/text mounts, cvgserver).  The only dependencies
       come from hard-coded pathnames like /usr/local.  However, your host
       system and Cygwin configuration will affect Perl's runtime behavior
       (see "TEST").

       o   "PATH"

           Set the "PATH" environment variable so that Configure finds the
           Cygwin versions of programs. Any not-needed Windows directories
           should be removed or moved to the end of your "PATH".

       o   nroff

           If you do not have nroff (which is part of the groff package),
           Configure will not prompt you to install man pages.


       The default options gathered by Configure with the assistance of
       hints/ will build a Perl that supports dynamic loading (which
       requires a shared cygperl5_16.dll).

       This will run Configure and keep a record:

         ./Configure 2>&1 | tee log.configure

       If you are willing to accept all the defaults run Configure with -de.
       However, several useful customizations are available.

   Stripping Perl Binaries on Cygwin
       It is possible to strip the EXEs and DLLs created by the build process.
       The resulting binaries will be significantly smaller.  If you want the
       binaries to be stripped, you can either add a -s option when Configure
       prompts you,

         Any additional ld flags (NOT including libraries)? [none] -s
         Any special flags to pass to g++ to create a dynamically loaded
         [none] -s
         Any special flags to pass to gcc to use dynamic linking? [none] -s

       or you can edit hints/ and uncomment the relevant variables
       near the end of the file.

   Optional Libraries for Perl on Cygwin
       Several Perl functions and modules depend on the existence of some
       optional libraries.  Configure will find them if they are installed in
       one of the directories listed as being used for library searches.  Pre-
       built packages for most of these are available from the Cygwin

       o   "-lcrypt"

           The crypt package distributed with Cygwin is a Linux compatible
           56-bit DES crypt port by Corinna Vinschen.

           Alternatively, the crypt libraries in GNU libc have been ported to

           As of libcrypt 1.3 (March 2016), you will need to install the
           libcrypt-devel package for Configure to detect crypt().

       o   "-lgdbm_compat" ("use GDBM_File")

           GDBM is available for Cygwin.

           NOTE: The GDBM library only works on NTFS partitions.

       o   "-ldb" ("use DB_File")

           BerkeleyDB is available for Cygwin.

           NOTE: The BerkeleyDB library only completely works on NTFS

       o   "cygserver" ("use IPC::SysV")

           A port of SysV IPC is available for Cygwin.

           NOTE: This has not been extensively tested.  In particular,
           "d_semctl_semun" is undefined because it fails a Configure test and
           on Win9x the shm*() functions seem to hang.  It also creates a
           compile time dependency because perl.h includes <sys/ipc.h> and
           <sys/sem.h> (which will be required in the future when compiling
           CPAN modules). CURRENTLY NOT SUPPORTED!

       o   "-lutil"

           Included with the standard Cygwin netrelease is the inetutils
           package which includes libutil.a.

   Configure-time Options for Perl on Cygwin
       The INSTALL document describes several Configure-time options.  Some of
       these will work with Cygwin, others are not yet possible.  Also, some
       of these are experimental.  You can either select an option when
       Configure prompts you or you can define (undefine) symbols on the
       command line.

       o   "-Uusedl"

           Undefining this symbol forces Perl to be compiled statically.

       o   "-Dusemymalloc"

           By default Perl does not use the "malloc()" included with the Perl
           source, because it was slower and not entirely thread-safe.  If you
           want to force Perl to build with the old -Dusemymalloc define this.

       o   "-Uuseperlio"

           Undefining this symbol disables the PerlIO abstraction.  PerlIO is
           now the default; it is not recommended to disable PerlIO.

       o   "-Dusemultiplicity"

           Multiplicity is required when embedding Perl in a C program and
           using more than one interpreter instance.  This is only required
           when you build a not-threaded perl with "-Uuseithreads".

       o   "-Uuse64bitint"

           By default Perl uses 64 bit integers.  If you want to use smaller
           32 bit integers, define this symbol.

       o   "-Duselongdouble"

           gcc supports long doubles (12 bytes).  However, several additional
           long double math functions are necessary to use them within Perl
           ({atan2, cos, exp, floor, fmod, frexp, isnan, log, modf, pow, sin,
           sqrt}l, strtold).  These are not yet available with newlib, the
           Cygwin libc.

       o   "-Uuseithreads"

           Define this symbol if you want not-threaded faster perl.

       o   "-Duselargefiles"

           Cygwin uses 64-bit integers for internal size and position
           calculations, this will be correctly detected and defined by

       o   "-Dmksymlinks"

           Use this to build perl outside of the source tree.  Details can be
           found in the INSTALL document.  This is the recommended way to
           build perl from sources.

   Suspicious Warnings on Cygwin
       You may see some messages during Configure that seem suspicious.

       o   Win9x and "d_eofnblk"

           Win9x does not correctly report "EOF" with a non-blocking read on a
           closed pipe.  You will see the following messages:

            But it also returns -1 to signal EOF, so be careful!
            WARNING: you can't distinguish between EOF and no data!

            *** WHOA THERE!!! ***
                The recommended value for $d_eofnblk on this machine was
                Keep the recommended value? [y]

           At least for consistency with WinNT, you should keep the
           recommended value.

       o   Compiler/Preprocessor defines

           The following error occurs because of the Cygwin "#define" of

             Guessing which symbols your C compiler and preprocessor define...
             try.c:<line#>: missing binary operator

           This failure does not seem to cause any problems.  With older gcc
           versions, "parse error" is reported instead of "missing binary


       Simply run make and wait:

         make 2>&1 | tee log.make


       There are two steps to running the test suite:

         make test 2>&1 | tee log.make-test

         cd t; ./perl harness 2>&1 | tee ../log.harness

       The same tests are run both times, but more information is provided
       when running as "./perl harness".

       Test results vary depending on your host system and your Cygwin
       configuration.  If a test can pass in some Cygwin setup, it is always
       attempted and explainable test failures are documented.  It is possible
       for Perl to pass all the tests, but it is more likely that some tests
       will fail for one of the reasons listed below.

   File Permissions on Cygwin
       UNIX file permissions are based on sets of mode bits for
       {read,write,execute} for each {user,group,other}.  By default Cygwin
       only tracks the Win32 read-only attribute represented as the UNIX file
       user write bit (files are always readable, files are executable if they
       have a .{com,bat,exe} extension or begin with "#!", directories are
       always readable and executable).  On WinNT with the ntea "CYGWIN"
       setting, the additional mode bits are stored as extended file
       attributes.  On WinNT with the default ntsec "CYGWIN" setting,
       permissions use the standard WinNT security descriptors and access
       control lists. Without one of these options, these tests will fail
       (listing not updated yet):

         Failed Test           List of failed
         io/fs.t               5, 7, 9-10
         lib/anydbm.t          2
         lib/db-btree.t        20
         lib/db-hash.t         16
         lib/db-recno.t        18
         lib/gdbm.t            2
         lib/ndbm.t            2
         lib/odbm.t            2
         lib/sdbm.t            2
         op/stat.t             9, 20 (.tmp not an executable extension)

   NDBM_File and ODBM_File do not work on FAT filesystems
       Do not use NDBM_File or ODBM_File on FAT filesystem.  They can be built
       on a FAT filesystem, but many tests will fail:

        ../ext/NDBM_File/ndbm.t       13  3328    71   59  83.10%  1-2 4 16-71
        ../ext/ODBM_File/odbm.t      255 65280    ??   ??       %  ??
        ../lib/AnyDBM_File.t           2   512    12    2  16.67%  1 4
        ../lib/Memoize/t/errors.t      0   139    11    5  45.45%  7-11
        ../lib/Memoize/t/tie_ndbm.t   13  3328     4    4 100.00%  1-4
        run/fresh_perl.t                          97    1   1.03%  91

       If you intend to run only on FAT (or if using AnyDBM_File on FAT), run
       Configure with the -Ui_ndbm and -Ui_dbm options to prevent NDBM_File
       and ODBM_File being built.

       With NTFS (and no CYGWIN=nontsec), there should be no problems even if
       perl was built on FAT.

   "fork()" failures in io_* tests
       A "fork()" failure may result in the following tests failing:


       See comment on fork in "Miscellaneous" below.

Specific features of the Cygwin port

   Script Portability on Cygwin
       Cygwin does an outstanding job of providing UNIX-like semantics on top
       of Win32 systems.  However, in addition to the items noted above, there
       are some differences that you should know about.  This is a very brief
       guide to portability, more information can be found in the Cygwin

       o   Pathnames

           Cygwin pathnames are separated by forward (/) slashes, Universal
           Naming Codes (//UNC) are also supported Since cygwin-1.7 non-POSIX
           pathnames are discouraged.  Names may contain all printable

           File names are case insensitive, but case preserving.  A pathname
           that contains a backslash or drive letter is a Win32 pathname, and
           not subject to the translations applied to POSIX style pathnames,
           but cygwin will warn you, so better convert them to POSIX.

           For conversion we have "Cygwin::win_to_posix_path()" and

           Since cygwin-1.7 pathnames are UTF-8 encoded.

       o   Text/Binary

           Since cygwin-1.7 textmounts are deprecated and strongly

           When a file is opened it is in either text or binary mode.  In text
           mode a file is subject to CR/LF/Ctrl-Z translations.  With Cygwin,
           the default mode for an "open()" is determined by the mode of the
           mount that underlies the file. See "Cygwin::is_binmount"(). Perl
           provides a "binmode()" function to set binary mode on files that
           otherwise would be treated as text.  "sysopen()" with the "O_TEXT"
           flag sets text mode on files that otherwise would be treated as

               sysopen(FOO, "bar", O_WRONLY|O_CREAT|O_TEXT)

           "lseek()", "tell()" and "sysseek()" only work with files opened in
           binary mode.

           The text/binary issue is covered at length in the Cygwin

       o   PerlIO

           PerlIO overrides the default Cygwin Text/Binary behaviour.  A file
           will always be treated as binary, regardless of the mode of the
           mount it lives on, just like it is in UNIX.  So CR/LF translation
           needs to be requested in either the "open()" call like this:

             open(FH, ">:crlf", "out.txt");

           which will do conversion from LF to CR/LF on the output, or in the
           environment settings (add this to your .bashrc):

             export PERLIO=crlf

           which will pull in the crlf PerlIO layer which does LF -> CRLF
           conversion on every output generated by perl.

       o   .exe

           The Cygwin "stat()", "lstat()" and "readlink()" functions make the
           .exe extension transparent by looking for foo.exe when you ask for
           foo (unless a foo also exists).  Cygwin does not require a .exe
           extension, but gcc adds it automatically when building a program.
           However, when accessing an executable as a normal file (e.g., cp in
           a makefile) the .exe is not transparent.  The install program
           included with Cygwin automatically appends a .exe when necessary.

       o   Cygwin vs. Windows process ids

           Cygwin processes have their own pid, which is different from the
           underlying windows pid.  Most posix compliant Proc functions expect
           the cygwin pid, but several Win32::Process functions expect the
           winpid. E.g. $$ is the cygwin pid of /usr/bin/perl, which is not
           the winpid.  Use "Cygwin::pid_to_winpid()" and
           "Cygwin::winpid_to_pid()" to translate between them.

       o   Cygwin vs. Windows errors

           Under Cygwin, $^E is the same as $!.  When using Win32 API
           Functions, use "Win32::GetLastError()" to get the last Windows

       o   rebase errors on fork or system

           Using "fork()" or "system()" out to another perl after loading
           multiple dlls may result on a DLL baseaddress conflict. The
           internal cygwin error looks like like the following:

            0 [main] perl 8916 child_info_fork::abort: data segment start:
            parent (0xC1A000) != child(0xA6A000)


            183 [main] perl 3588 C:\cygwin\bin\perl.exe: *** fatal error -
            unable to remap C:\cygwin\bin\cygsvn_subr-1-0.dll to same address
            as parent(0x6FB30000) != 0x6FE60000 46 [main] perl 3488 fork: child
            3588 - died waiting for dll loading, errno11

           It helps if not too many DLLs are loaded in memory so the available
           address space is larger, e.g. stopping the MS Internet Explorer
           might help.

           Use the perlrebase or rebase utilities to resolve the conflicting
           dll addresses.  The rebase package is included in the Cygwin setup.
           Use setup.exe from <> to install it.

           1. kill all perl processes and run "perlrebase" or

           2. kill all cygwin processes and services, start dash from cmd.exe
           and run "rebaseall".

       o   "chown()"

           On WinNT "chown()" can change a file's user and group IDs.  On
           Win9x "chown()" is a no-op, although this is appropriate since
           there is no security model.

       o   Miscellaneous

           File locking using the "F_GETLK" command to "fcntl()" is a stub
           that returns "ENOSYS".

           Win9x can not "rename()" an open file (although WinNT can).

           The Cygwin "chroot()" implementation has holes (it can not restrict
           file access by native Win32 programs).

           Inplace editing "perl -i" of files doesn't work without doing a
           backup of the file being edited "perl -i.bak" because of windowish
           restrictions, therefore Perl adds the suffix ".bak" automatically
           if you use "perl -i" without specifying a backup extension.

   Prebuilt methods:
           Returns the current working directory.

           Translates a cygwin pid to the corresponding Windows pid (which may
           or may not be the same).

           Translates a Windows pid to the corresponding cygwin pid (if any).

           Translates a Windows path to the corresponding cygwin path
           respecting the current mount points. With a second non-null
           argument returns an absolute path. Double-byte characters will not
           be translated.

           Translates a cygwin path to the corresponding cygwin path
           respecting the current mount points. With a second non-null
           argument returns an absolute path. Double-byte characters will not
           be translated.

           Returns an array of [mnt_dir, mnt_fsname, mnt_type, mnt_opts].

             perl -e 'for $i (Cygwin::mount_table) {print join(" ",@$i),"\n";}'
             /bin c:\cygwin\bin system binmode,cygexec
             /usr/bin c:\cygwin\bin system binmode
             /usr/lib c:\cygwin\lib system binmode
             / c:\cygwin system binmode
             /cygdrive/c c: system binmode,noumount
             /cygdrive/d d: system binmode,noumount
             /cygdrive/e e: system binmode,noumount

           Returns the mount type and flags for a specified mount point.  A
           comma-separated string of mntent->mnt_type (always "system" or
           "user"), then the mntent->mnt_opts, where the first is always
           "binmode" or "textmode".


           If the argument is "/cygdrive", then just the volume mount
           settings, and the cygdrive mount prefix are returned.

           User mounts override system mounts.

             $ perl -e 'print Cygwin::mount_flags "/usr/bin"'
             $ perl -e 'print Cygwin::mount_flags "/cygdrive"'

           Returns true if the given cygwin path is binary mounted, false if
           the path is mounted in textmode.

           Cygwin does not initialize all original Win32 environment
           variables.  See the bottom of this page
           <> for "Restricted
           Win32 environment".

           Certain Win32 programs called from cygwin programs might need some
           environment variable, such as e.g. ADODB needs
           %COMMONPROGRAMFILES%.  Call Cygwin::sync_winenv() to copy all Win32
           environment variables to your process and note that cygwin will
           warn on every encounter of non-POSIX paths.


       This will install Perl, including man pages.

         make install 2>&1 | tee log.make-install

       NOTE: If "STDERR" is redirected "make install" will not prompt you to
       install perl into /usr/bin.

       You may need to be Administrator to run "make install".  If you are
       not, you must have write access to the directories in question.

       Information on installing the Perl documentation in HTML format can be
       found in the INSTALL document.


       These are the files in the Perl release that contain references to
       Cygwin.  These very brief notes attempt to explain the reason for all
       conditional code.  Hopefully, keeping this up to date will allow the
       Cygwin port to be kept as clean as possible.

            INSTALL README.cygwin README.win32 MANIFEST
            pod/perl.pod pod/perlport.pod pod/perlfaq3.pod
            pod/perldelta.pod pod/perl5004delta.pod pod/perl56delta.pod
            pod/perl561delta.pod pod/perl570delta.pod pod/perl572delta.pod
            pod/perl573delta.pod pod/perl58delta.pod pod/perl581delta.pod
            pod/perl590delta.pod pod/perlhist.pod pod/perlmodlib.pod
            pod/perltoc.pod Porting/Glossary pod/perlgit.pod
            dist/Cwd/Changes ext/Compress-Raw-Zlib/Changes
            ext/Compress-Raw-Zlib/README ext/Compress-Zlib/Changes
            ext/DB_File/Changes ext/Encode/Changes ext/Sys-Syslog/Changes
            lib/ExtUtils/CBuilder/Changes lib/ExtUtils/Changes
            lib/ExtUtils/NOTES lib/ExtUtils/PATCHING lib/ExtUtils/README
            lib/Net/Ping/Changes lib/Test/Harness/Changes
            lib/Term/ANSIColor/ChangeLog lib/Term/ANSIColor/README

       Build, Configure, Make, Install
            Configure             - help finding hints from uname,
                                    shared libperl required for dynamic loading
            Makefile.SH Cross/Makefile-cross-SH
                                  - linklibperl
            Porting/patchls       - cygwin in port list
            installman            - man pages with :: translated to .
            installperl           - install dll, install to 'pods'
            makedepend.SH         - uwinfix
            - file permissions


            t/io/fs.t             - no file mode checks if not ntsec
                                    skip rename() check when not
            t/io/tell.t           - binmode
            t/lib/cygwin.t        - builtin cygwin function tests
            t/op/groups.t         - basegroup has ID = 0
            t/op/magic.t          - $^X/symlink WORKAROUND, s/.exe//
            t/op/stat.t           - no /dev, skip Win32 ftCreationTime quirk
                                    (cache manager sometimes preserves ctime of
                                    file previously created and deleted), no -u
            t/op/taint.t          - can't use empty path under Cygwin Perl
            t/op/time.t           - no tzset()

       Compiled Perl Source
            EXTERN.h              - __declspec(dllimport)
            XSUB.h                - __declspec(dllexport)
            cygwin/cygwin.c       - os_extras (getcwd, spawn, and several
                                    Cygwin:: functions)
            perl.c                - os_extras, -i.bak
            perl.h                - binmode
            doio.c                - win9x can not rename a file when it is open
            pp_sys.c              - do not define h_errno, init
            util.c                - use setenv
            util.h                - PERL_FILE_IS_ABSOLUTE macro
            pp.c                  - Comment about Posix vs IEEE math under
            perlio.c              - CR/LF mode
            perliol.c             - Comment about EXTCONST under Cygwin

       Compiled Module Source
                                  - Can't install via CPAN shell under Cygwin
                                  - Cygwin is Unix-like and has vsnprintf
            ext/Errno/Errno_pm.PL - Special handling for Win32 Perl under
            ext/POSIX/POSIX.xs    - tzname defined externally
                                  - EXTCONST needs to be redefined from
                                  - binary open
                                  - Cygwin has syslog.h
                                  - Convert paths to Windows paths
                                  - Various timers not available
                                  - Find w32api/windows.h
            ext/Win32/Makefile.PL - Use various libraries under Cygwin
            ext/Win32/Win32.xs    - Child dir and child env under Cygwin
                                  - _open_osfhandle not implemented under
                                  - __declspec(dllexport)

       Perl Modules/Scripts
            ext/B/t/ - Comment about stderr/stdout order under
                                  - Use binary mode under Cygwin
                                  - Convert paths to Windows paths
                                  - Comment about various timers not available
                                  - _open_osfhandle not implemented under
                                  - History of Win32CORE under Cygwin
            lib/            - hook to internal Cwd::cwd
                                  - use gcc for ld, and link to libperl.dll.a
                                  - Cygwin is Unix-like
            lib/ExtUtils/ - Install and rename issues under Cygwin
            lib/ExtUtils/    - OS classifications
            lib/ExtUtils/ - Example for Cygwin
                                  - require
                                  - canonpath, cflags, manifypods, perl_archive
            lib/File/     - Comment about quotes using a Cygwin example
            lib/File/      - on remote drives stat() always sets
                                    st_nlink to 1
            lib/File/Spec/ - case_tolerant
            lib/File/Spec/ - preserve //unc
            lib/File/Spec/ - References a message on
            lib/File/      - Pulls in lib/File/Spec/
            lib/File/      - no directory sticky bit
            lib/Module/ - List of all module files and versions
            lib/Net/     - No domainname command under Cygwin
            lib/Net/      - Bypass using stat() under Cygwin
            lib/Net/       - ECONREFUSED is EAGAIN under Cygwin
            lib/Pod/       - Set 'pods' dir
            lib/Pod/Perldoc/ - '-c' switch for pod2man
            lib/Pod/    - Use 'less' pager, and use .exe extension
            lib/Term/ - Cygwin terminal info
            lib/        - use stdin not /dev/tty
            utils/perlbug.PL      - Add CYGWIN environment variable to report

       Perl Module Tests


       Support for swapping real and effective user and group IDs is
       incomplete.  On WinNT Cygwin provides "setuid()", "seteuid()",
       "setgid()" and "setegid()".  However, additional Cygwin calls for
       manipulating WinNT access tokens and security contexts are required.


       Charles Wilson <>, Eric Fifer
       <>, alexander smishlajev <>, Steven
       Morlock <>, Sebastien Barre
       <>, Teun Burgers <>, Gerrit P.
       Haase <>, Reini Urban <>, Jan Dubois
       <>, Jerry D. Hedden <>.


       Last updated: 2012-02-08

perl v5.34.0                      2021-02-21                   PERLCYGWIN(1pm)

perl 5.34.0 - Generated Fri Feb 25 15:57:35 CST 2022
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