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 1.5.2 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).


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.

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.

Suspicious Warnings on Cygwin

You may see some messages during Configure that seem suspicious.


Simply run make and wait:

  make 2>&1 | tee log.make

Errors on Cygwin

Errors like these are normal:

  make: [extra.pods] Error 1 (ignored)
  make: [extras.make] Error 1 (ignored)

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 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 CYGWIN=ntsec), 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 documentation.

Prebuilt methods:


Returns 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).


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 perl/buildtoc 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)
  t/lib/cygwin.t        - builtin cygwin function tests
Compiled Perl Source
  EXTERN.h              - __declspec(dllimport)
  XSUB.h                - __declspec(dllexport)
  cygwin/cygwin.c       - os_extras (getcwd, spawn, Cygwin::winpid_to_pid, 
  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 P. Haase <>.


Last updated: 2005-02-11