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README .cygwin − 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 on the Cygwin CD . If you do not need to customize the configuration, consider using one of these packages:



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 1.1.5 was current.

NOTE: At this point, minimal effort has been made to provide compatibility with old (beta) Cygwin releases. The focus has been to provide a high quality release and not worry about working around old bugs. If you wish to use Perl with Cygwin B20.1 or earlier, consider using perl5.005_03, which is available in source and binary form at "http://cygutils.netpedia.net/". If there is significant demand, a patch kit can be developed to port back to earlier Cygwin versions.

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 (Win9x/WinME, WinNT/Win2K) or your Cygwin configuration (ntea, ntsec, binary/text mounts). 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 the TEST entry elsewhere in this document).

Set the "PATH" environment variable so that Configure finds the Cygwin versions of programs. Any Windows directories should be removed or moved to the end of your "PATH".


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

• Permissions

On WinNT with either the ntea or ntsec "CYGWIN" settings, directory and file permissions may not be set correctly. Since the build process creates directories and files, to be safe you may want to run a ’"chmod −R +w *"’ on the entire Perl source tree.

Also, it is a well known WinNT "feature" that files created by a login that is a member of the Administrators group will be owned by the Administrators group. Depending on your umask, you may find that you can not write to files that you just created (because you are no longer the owner). When using the ntsec "CYGWIN" setting, this is not an issue because it "corrects" the ownership to what you would expect on a UNIX system.


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

Strip Binaries

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 gcc to use dynamic linking? [none] -s
  Any special flags to pass to ld2 to create a dynamically loaded library?
  [none] -s

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

Optional Libraries

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 at "http://cygutils.netpedia.net/".

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 Cygwin.

The DES based Ultra Fast Crypt port was done by Alexey Truhan:


NOTE: There are various export restrictions on DES implementations, see the glibc README for more details.

The MD5 port was done by Andy Piper:


""−lgdbm"" (""use GDBM_File"")

GDBM is available for Cygwin. GDBM ’s ndbm/dbm compatibility feature also makes "NDBM_File" and "ODBM_File" possible (although they add little extra value).

NOTE: The ndbm/dbm emulations only completely work on NTFS partitions.

""−ldb"" (""use DB_File"")

BerkeleyDB is available for Cygwin. Some details can be found in ext/DB_File/DB_File.pm.

NOTE: The BerkeleyDB library only completely works on NTFS partitions.

""−lcygipc"" (""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).

Configure-time Options

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.

Undefining this symbol forces Perl to be compiled statically.


By default Perl uses the malloc() included with the Perl source. If you want to force Perl to build with the system malloc() undefine this symbol.


Multiplicity is required when embedding Perl in a C program and using more than one interpreter instance. This works with the Cygwin port.


The PerlIO abstraction works with the Cygwin port.


gcc supports 64−bit integers. However, several additional long long functions are necessary to use them within Perl ({strtol,strtoul}l). These are not yet available with Cygwin.


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 Cygwin.


POSIX threads are not yet implemented in Cygwin.


Although Win32 supports large files, Cygwin currently uses 32−bit integers for internal size and position calculations.

Suspicious Warnings

You may see some messages during Configure that seem suspicious.

ld2 is needed to build dynamic libraries, but it does not exist when dlsym() checking occurs (it is not created until ’"make"’ runs). You will see the following message:

  Checking whether your dlsym() needs a leading underscore ...
  ld2: not found
  I can’t compile and run the test program.
  I’m guessing that dlsym doesn’t need a leading underscore.

Since the guess is correct, this is not a problem.

• 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 "define"!
      Keep the recommended value? [y]

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

• Compiler/Preprocessor defines

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

  Guessing which symbols your C compiler and preprocessor define...
  try.c:<line#>: parse error

This failure does not seem to cause any problems.


Simply run make and wait:

  make 2>&1 ⎪ tee log.make


Warnings like these are normal:

  warning: overriding commands for target <file>
  warning: ignoring old commands for target <file>

  dllwrap: no export definition file provided
  dllwrap: creating one, but that may not be what you want


During ’"make"’, ld2 will be created and installed in your $installbin directory (where you said to put public executables). It does not wait until the ’"make install"’ process to install the ld2 script, this is because the remainder of the ’"make"’ refers to ld2 without fully specifying its path and does this from multiple subdirectories. The assumption is that $installbin is in your current "PATH". If this is not the case ’"make"’ will fail at some point. If this happens, just manually copy ld2 from the source directory to somewhere in your "PATH".


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

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 ntsec "CYGWIN" setting, permissions use the standard WinNT security descriptors and access control lists. Without one of these options, these tests will fail:

  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)

Hard Links

FAT partitions do not support hard links (whereas NTFS does), in which case Cygwin implements link() by copying the file. On remote (network) drives Cygwin’s stat() always sets "st_nlink" to 1, so the link count for remote directories and files is not available. In either case, these tests will fail:

  Failed Test           List of failed
  io/fs.t               4
  op/stat.t             3

Filetime Granularity

On FAT partitions the filetime granularity is 2 seconds. The following test will fail:

  Failed Test           List of failed
  io/fs.t               18

Tainting Checks

When Perl is running in taint mode, "$ENV{PATH}" is considered tainted and not used, so DLLs not in the default system directories will not be found. While the tests are running you will see warnings popup from the system with messages like:

    Error Starting Program
    A required .DLL file, CYGWIN1.DLL, was not found

    perl.exe - Unable to Locate DLL
    The dynamic link library cygwin1.dll could not be found in the
      specified path ...

Just click OK and ignore them. When running ’"make test"’, 2 popups occur. During ’"./perl harness"’, 4 popups occur. Also, these tests will fail:

  Failed Test           List of failed
  op/taint.t            1, 3, 31, 37

Alternatively, you can copy cygwin1.dll into the directory where the tests run:

  cp /bin/cygwin1.dll t

or one of the Windows system directories (although, this is not recommended).


Cygwin does not require /etc/group, in which case the op/grent.t test will be skipped. The check performed by op/grent.t expects to see entries that use the members field, otherwise this test will fail:

  Failed Test           List of failed
  op/grent.t            1

Script Portability

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 documentation.
• Pathnames

Cygwin pathnames can be separated by forward (/) or backward (\) slashes. They may also begin with drive letters (C:) or Universal Naming Codes (//UNC). DOS device names (aux, con, prn, com*, lpt?, nul) are invalid as base filenames. However, they can be used in extensions (e.g., hello.aux). Names may contain all printable characters except these:

  : * ? " < > ⎪

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).

• Text/Binary

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. 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 binary:

    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 documentation.


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 included with Cygwin automatically appends a .exe when necessary.


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.

• 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).


This will install Perl, including man pages.

  make install ⎪ 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.

  Changes Changes5.005 Changes5.004 Changes5.6
  pod/perl.pod pod/perlport.pod pod/perlfaq3.pod
  pod/perldelta.pod pod/perl5004delta.pod pod/perl56delta.pod
  pod/perlhist.pod pod/perlmodlib.pod pod/buildtoc.PL pod/perltoc.pod

Build, Configure, Make, Install

  Configure             - help finding hints from uname,
                          shared libperl required for dynamic loading
  Makefile.SH           - linklibperl
  Porting/patchls       - cygwin in port list
  installman            - man pages with :: translated to .
  installperl           - install dll/ld2/perlld, install to pods
  makedepend.SH         - uwinfix


  t/io/tell.t           - binmode
  t/lib/b.t             - ignore Cwd from os_extras
  t/lib/glob-basic.t    - Win32 directory list access differs from read mode
  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 (setuid)

Compiled Perl Source

  EXTERN.h              - __declspec(dllimport)
  XSUB.h                - __declspec(dllexport)
  cygwin/cygwin.c       - os_extras (getcwd, spawn)
  perl.c                - os_extras
  perl.h                - binmode
  doio.c                - win9x can not rename a file when it is open
  pp_sys.c              - do not define h_errno, pp_system with spawn
  util.c                - use setenv

Compiled Module Source

  ext/POSIX/POSIX.xs    - tzname defined externally
                        - EXTCONST needs to be redefined from EXTERN.h
                        - binary open

Perl Modules/Scripts

  lib/Cwd.pm            - hook to internal Cwd::cwd
                        - require MM_Cygwin.pm
                        - canonpath, cflags, manifypods, perl_archive
  lib/File/Find.pm      - on remote drives stat() always sets st_nlink to 1
  lib/File/Spec/Unix.pm - preserve //unc
  lib/File/Temp.pm      - no directory sticky bit
  lib/perl5db.pl        - use stdin not /dev/tty
  utils/perldoc.PL      - version comment


When make starts, it warns about overriding commands for perlmain.o.

"make clean"’ does not remove library .def or .exe.stackdump files.

The ld2 script contains references to the source directory. You should change these to $installbin after ’"make install"’.

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.

When building DLLs, ’"dllwrap −−export−all−symbols"’ is used to export global symbols. It might be better to generate an explicit .def file (see makedef.pl). Also, DLLs can now be build with ’"gcc −shared"’.


Charles Wilson <cwilson@ece.gatech.edu>, Eric Fifer <egf7@columbia.edu>, alexander smishlajev <als@turnhere.com>, Steven Morlock <newspost@morlock.net>, Sebastien Barre <Sebastien.Barre@utc.fr>, Teun Burgers <burgers@ecn.nl>.


Last updated: 9 November 2000