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 in the normal Cygwin install. If you do not need to customize the configuration, consider using one of those 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 1.3.12 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 (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 /"TEST").

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.
* nroff
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/ 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.

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 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/ 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 installer.

* -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 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.
* -ldb (use DB_File)

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

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). NO LONGER SUPPORTED!

* -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.

* -Uusedl
Undefining this symbol forces Perl to be compiled statically.
* -Uusemymalloc
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.
* -Uuseperlio
Undefining this symbol disables the PerlIO abstraction, which is now the default.
* -Dusemultiplicity
Multiplicity is required when embedding Perl in a C program and using more than one interpreter instance. This works with the Cygwin port.
* -Duse64bitint
By default Perl uses 32 bit integers. If you want to use larger 64 bit integers, define this symbol. If there is trouble, check that your Cygwin installation is up to date.
* -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 Cygwin.
* -Dusethreads
POSIX threads are not yet implemented in Cygwin completely.
* -Duselargefiles
Although Win32 supports large files, Cygwin currently uses 32-bit integers for internal size and position calculations.
* -Dmksymlinks
Use this to build perl outside of the source tree. This works with Cygwin. Details can be found in the INSTALL document.

Suspicious Warnings on Cygwin

You may see some messages during Configure that seem suspicious.

* dlsym()

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 on Cygwin

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

ld2 on Cygwin

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 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 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 does not work on FAT filesystems

Do not install NDBM_File on FAT filesystem. It can be built on a FAT filesystem, but many ndbm tests will fail. With NTFS, there should be no problems either way.

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 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.

* .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 included with Cygwin automatically appends a .exe when necessary.
* 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.
* 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, so Perl adds the .bak automatically if you just use perl -i.


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 (listing not updated yet).

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


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 Haase <>.


Last updated: 2002-02-27