Cygwin Utilities

Cygwin comes with a number of command-line utilities that are used to manage the UNIX emulation portion of the Cygwin environment. While many of these reflect their UNIX counterparts, each was written specifically for Cygwin. You may use the long or short option names interchangeably; for example, --help and -h function identically. All of the Cygwin command-line utilities support the --help and --version options.


Usage: cygcheck PROGRAM [ -v ] [ -h ]
       cygcheck -c [ PACKAGE ... ] [ -d ]
       cygcheck -s [ -r ] [ -v ] [ -h ]
       cygcheck -k
       cygcheck -f FILE [ FILE ... ]
       cygcheck -l [ PACKAGE ... ]
       cygcheck -p REGEXP
List system information, check installed packages, or query package database.

At least one command option or a PROGRAM is required, as shown above.

  PROGRAM              list library (DLL) dependencies of PROGRAM
  -c, --check-setup    show installed version of PACKAGE and verify integrity
                       (or for all installed packages if none specified)
  -d, --dump-only      just list packages, do not verify (with -c)
  -s, --sysinfo        produce diagnostic system information (implies -c -d)
  -r, --registry       also scan registry for Cygwin settings (with -s)
  -k, --keycheck       perform a keyboard check session (must be run from a
                       plain console only, not from a pty/rxvt/xterm)
  -f, --find-package   find the package that FILE belongs to
  -l, --list-package   list contents of PACKAGE (or all packages if none given)
  -p, --package-query  search for REGEXP in the entire package
                       repository (requies internet connectivity)
  -v, --verbose        produce more verbose output
  -h, --help           annotate output with explanatory comments when given
                       with another command, otherwise print this help
  -V, --version        print the version of cygcheck and exit

Note: -c, -f, and -l only report on packages that are currently installed. To
  search all official Cygwin packages use -p instead.  The -p REGEXP matches
  package names, descriptions, and names of files/paths within all packages.

The cygcheck program is a diagnostic utility for dealing with Cygwin programs. If you are familiar with dpkg or rpm, cygcheck is similar in many ways. (The major difference is that setup.exe handles installing and uninstalling packages; see the section called “Internet Setup” for more information.)

The -c option checks the version and status of installed Cygwin packages. If you specify one or more package names, cygcheck will limit its output to those packages, or with no arguments it lists all packages. A package will be marked Incomplete if files originally installed are no longer present. The best thing to do in that situation is reinstall the package with setup.exe. To see which files are missing, use the -v option. If you do not need to know the status of each package and want cygcheck to run faster, add the -d option and cygcheck will only output the name and version for each package.

If you list one or more programs on the command line, cygcheck will diagnose the runtime environment of that program or programs, providing the names of DLL files on which the program depends. If you specify the -s option, cygcheck will give general system information. If you list one or more programs on the command line and specify -s, cygcheck will report on both.

The -f option helps you to track down which package a file came from, and -l lists all files in a package. For example, to find out about /usr/bin/less and its package:

Example 3.3. Example cygcheck usage

$ cygcheck -f /usr/bin/less

$ cygcheck -l less

The -h option prints additional helpful messages in the report, at the beginning of each section. It also adds table column headings. While this is useful information, it also adds some to the size of the report, so if you want a compact report or if you know what everything is already, just leave this out.

The -v option causes the output to be more verbose. What this means is that additional information will be reported which is usually not interesting, such as the internal version numbers of DLLs, additional information about recursive DLL usage, and if a file in one directory in the PATH also occurs in other directories on the PATH.

The -r option causes cygcheck to search your registry for information that is relevent to Cygwin programs. These registry entries are the ones that have "Cygwin" in the name. If you are paranoid about privacy, you may remove information from this report, but please keep in mind that doing so makes it harder to diagnose your problems.

In contrast to the other options that search the packages that are installed on your local system, the -p option can be used to search the entire official Cygwin package repository. It takes as argument a Perl-compatible regular expression which is used to match package names, package descriptions, and path/filenames of the contents of packages. This feature requires an active internet connection, since it must query the web site. In fact, it is equalivant to the search that is available on the Cygwin package listing page.

For example, perhaps you are getting an error because you are missing a certain DLL and you want to know which package includes that file:

Example 3.4. Searching all packages for a file

$ cygcheck -p 'cygintl-2\.dll'
Found 1 matches for 'cygintl-2\.dll'.

libintl2-0.12.1-3         GNU Internationalization runtime library

$ cygcheck -p 'libexpat.*\.a'
Found 2 matches for 'libexpat.*\.a'.

expat-1.95.7-1            XML parser library written in C
expat-1.95.8-1            XML parser library written in C

$ cygcheck -p '/ls\.exe'
Found 2 matches for '/ls\.exe'.

coreutils-5.2.1-5         GNU core utilities (includes fileutils, sh-utils and textutils)
coreutils-5.3.0-6         GNU core utilities (includes fileutils, sh-utils and textutils)

Note that this option takes a regular expression, not a glob or wildcard. This means that you need to use .* if you want something similar to the wildcard * commonly used in filename globbing. Similarly, to match the period character you should use \. since the . character in a regexp is a metacharacter that will match any character. Also be aware that the characters such as \ and * are shell metacharacters, so they must be either escaped or quoted, as in the example above.

The third example above illustrates that if you want to match a whole filename, you should include the / path seperator. In the given example this ensures that filenames that happen to end in ls.exe such as ncftpls.exe are not shown. Note that this use does not mean "look for packages with ls in the root directory," since the / can match anywhere in the path. It's just there to anchor the match so that it matches a full filename.

By default the matching is case-sensitive. To get a case insensitive match, begin your regexp with (?i) which is a PCRE-specific feature. For complete documentation on Perl-compatible regular expression syntax and options, read the perlre manpage, or one of many websites such as that document the Perl language.

The cygcheck program should be used to send information about your system for troubleshooting when requested. When asked to run this command save the output so that you can email it, for example:

C:\cygwin> cygcheck -s -v -r -h > cygcheck_output.txt


Usage: cygpath (-d|-m|-u|-w|-t TYPE) [-f FILE] [OPTION]... NAME...
       cygpath [-c HANDLE] 
       cygpath [-ADHPSW] 
Convert Unix and Windows format paths, or output system path information

Output type options:
  -d, --dos             print DOS (short) form of NAMEs (C:\PROGRA~1\)
  -m, --mixed           like --windows, but with regular slashes (C:/WINNT)
  -M, --mode		report on mode of file (currently binmode or textmode)
  -u, --unix            (default) print Unix form of NAMEs (/cygdrive/c/winnt)
  -w, --windows         print Windows form of NAMEs (C:\WINNT)
  -t, --type TYPE       print TYPE form: 'dos', 'mixed', 'unix', or 'windows'
Path conversion options:
  -a, --absolute        output absolute path
  -l, --long-name       print Windows long form of NAMEs (with -w, -m only)
  -p, --path            NAME is a PATH list (i.e., '/bin:/usr/bin')
  -s, --short-name      print DOS (short) form of NAMEs (with -w, -m only)
System information:
  -A, --allusers        use `All Users' instead of current user for -D, -P
  -D, --desktop         output `Desktop' directory and exit
  -H, --homeroot        output `Profiles' directory (home root) and exit
  -P, --smprograms      output Start Menu `Programs' directory and exit
  -S, --sysdir          output system directory and exit
  -W, --windir          output `Windows' directory and exit
Other options:
  -f, --file FILE       read FILE for input; use - to read from STDIN
  -o, --option          read options from FILE as well (for use with --file)
  -c, --close HANDLE    close HANDLE (for use in captured process)
  -i, --ignore          ignore missing argument
  -h, --help            output usage information and exit
  -v, --version         output version information and exit

The cygpath program is a utility that converts Windows native filenames to Cygwin POSIX-style pathnames and vice versa. It can be used when a Cygwin program needs to pass a file name to a native Windows program, or expects to get a file name from a native Windows program. Alternatively, cygpath can output information about the location of important system directories in either format.

The -u and -w options indicate whether you want a conversion to UNIX (POSIX) format (-u) or to Windows format (-w). Use the -d to get DOS-style (8.3) file and path names. The -m option will output Windows-style format but with forward slashes instead of backslashes. This option is especially useful in shell scripts, which use backslashes as an escape character.

In combination with the -w option, you can use the -l and -s options to use normal (long) or DOS-style (short) form. The -d option is identical to -w and -s together.

Caveat: The -l option does not work if the check_case parameter of CYGWIN is set to strict, since Cygwin is not able to match any Windows short path in this mode.

The -p option means that you want to convert a path-style string rather than a single filename. For example, the PATH environment variable is semicolon-delimited in Windows, but colon-delimited in UNIX. By giving -p you are instructing cygpath to convert between these formats.

The -i option supresses the print out of the usage message if no filename argument was given. It can be used in make file rules converting variables that may be omitted to a proper format. Note that cygpath output may contain spaces (C:\Program Files) so should be enclosed in quotes.

Example 3.5. Example cygpath usage

if [ "${1}" = "" ];
		XPATH="$(cygpath -w "${1}")";
explorer $XPATH &

The capital options -D, -H, -P, -S, and -W output directories used by Windows that are not the same on all systems, for example -S might output C:\WINNT\SYSTEM32 or C:\WINDOWS\SYSTEM. The -H shows the Windows profiles directory that can be used as root of home. The -A option forces use of the "All Users" directories instead of the current user for the -D and -P options. On Win9x systems with only a single user, -A has no effect; -D and -AD would have the same output. By default the output is in UNIX (POSIX) format; use the -w or -d options to get other formats.


Dump core from WIN32PID to FILENAME.core

-d, --verbose  be verbose while dumping
-h, --help     output help information and exit
-q, --quiet    be quiet while dumping (default)
-v, --version  output version information and exit

The dumper utility can be used to create a core dump of running Windows process. This core dump can be later loaded to gdb and analyzed. One common way to use dumper is to plug it into cygwin's Just-In-Time debugging facility by adding


to the CYGWIN environment variable. Please note that x:\path\to\dumper.exe is Windows-style and not cygwin path. If error_start is set this way, then dumper will be started whenever some program encounters a fatal error.

dumper can be also be started from the command line to create a core dump of any running process. Unfortunately, because of a Windows API limitation, when a core dump is created and dumper exits, the target process is terminated too.

To save space in the core dump, dumper doesn't write those portions of target process' memory space that are loaded from executable and dll files and are unchangeable, such as program code and debug info. Instead, dumper saves paths to files which contain that data. When a core dump is loaded into gdb, it uses these paths to load appropriate files. That means that if you create a core dump on one machine and try to debug it on another, you'll need to place identical copies of the executable and dlls in the same directories as on the machine where the core dump was created.


Usage: getfacl [-adn] FILE [FILE2...]
Display file and directory access control lists (ACLs).

  -a, --all      display the filename, the owner, the group, and
                 the ACL of the file
  -d, --dir      display the filename, the owner, the group, and
                 the default ACL of the directory, if it exists
  -h, --help     output usage information and exit
  -n, --noname   display user and group IDs instead of names
  -v, --version  output version information and exit

When multiple files are specified on the command line, a blank
line separates the ACLs for each file.

For each argument that is a regular file, special file or directory, getfacl displays the owner, the group, and the ACL. For directories getfacl displays additionally the default ACL. With no options specified, getfacl displays the filename, the owner, the group, and both the ACL and the default ACL, if it exists. For more information on Cygwin and Windows ACLs, see see the section called “NT security and usage of ntsec” in the Cygwin User's Guide. The format for ACL output is as follows:

     # file: filename
     # owner: name or uid
     # group: name or uid
     user:name or uid:perm
     group:name or gid:perm
     default:user:name or uid:perm
     default:group:name or gid:perm


Usage: kill [-f] [-signal] [-s signal] pid1 [pid2 ...]
       kill -l [signal]
Send signals to processes

 -f, --force     force, using win32 interface if necessary
 -l, --list      print a list of signal names
 -s, --signal    send signal (use kill --list for a list)
 -h, --help      output usage information and exit
 -v, --version   output version information and exit

The kill program allows you to send arbitrary signals to other Cygwin programs. The usual purpose is to end a running program from some other window when ^C won't work, but you can also send program-specified signals such as SIGUSR1 to trigger actions within the program, like enabling debugging or re-opening log files. Each program defines the signals they understand.

You may need to specify the full path to use kill from within some shells, including bash, the default Cygwin shell. This is because bash defines a kill builtin function; see the bash man page under BUILTIN COMMANDS for more information. To make sure you are using the Cygwin version, try

$ /bin/kill --version

which should give the Cygwin kill version number and copyright information.

Unless you specific the -f option, the "pid" values used by kill are the Cygwin pids, not the Windows pids. To get a list of running programs and their Cygwin pids, use the Cygwin ps program. ps -W will display all windows pids.

The kill -l option prints the name of the given signal, or a list of all signal names if no signal is given.

To send a specific signal, use the -signN option, either with a signal number or a signal name (minus the "SIG" part), like these examples:

Example 3.6. Using the kill command

$ kill 123
$ kill -1 123
$ kill -HUP 123
$ kill -f 123

Here is a list of available signals, their numbers, and some commentary on them, from the file <sys/signal.h>, which should be considered the official source of this information.

SIGHUP       1    hangup
SIGINT       2    interrupt
SIGQUIT      3    quit
SIGILL       4    illegal instruction (not reset when caught)
SIGTRAP      5    trace trap (not reset when caught)
SIGABRT      6    used by abort
SIGEMT       7    EMT instruction
SIGFPE       8    floating point exception
SIGKILL      9    kill (cannot be caught or ignored)
SIGBUS      10    bus error
SIGSEGV     11    segmentation violation
SIGSYS      12    bad argument to system call
SIGPIPE     13    write on a pipe with no one to read it
SIGALRM     14    alarm clock
SIGTERM     15    software termination signal from kill
SIGURG      16    urgent condition on IO channel
SIGSTOP     17    sendable stop signal not from tty
SIGTSTP     18    stop signal from tty
SIGCONT     19    continue a stopped process
SIGCHLD     20    to parent on child stop or exit
SIGTTIN     21    to readers pgrp upon background tty read
SIGTTOU     22    like TTIN for output if (tp->t_local&LTOSTOP)
SIGPOLL     23    System V name for SIGIO
SIGXCPU     24    exceeded CPU time limit
SIGXFSZ     25    exceeded file size limit
SIGVTALRM   26    virtual time alarm
SIGPROF     27    profiling time alarm
SIGWINCH    28    window changed
SIGLOST     29    resource lost (eg, record-lock lost)
SIGUSR1     30    user defined signal 1
SIGUSR2     31    user defined signal 2


Usage: mkgroup [OPTION]... [domain]...
Prints /etc/group file to stdout

   -l,--local             print local group information
   -c,--current           print current group, if a domain account
   -d,--domain            print global group information (from current
                          domain if no domains specified).
   -o,--id-offset offset  change the default offset (10000) added to gids
                          in domain accounts.
   -s,--no-sids           don't print SIDs in pwd field
                          (this affects ntsec)
   -u,--users             print user list in gr_mem field
   -g,--group groupname   only return information for the specified group\n");
   -h,--help              print this message

   -v,--version           print version information and exit

One of `-l' or `-d' must be given on NT/W2K.

The mkgroup program can be used to help configure your Windows system to be more UNIX-like by creating an initial /etc/group. Its use is essential on the NT series (Windows NT, 2000, and XP) to include Windows security information. It can also be used on the Win9x series (Windows 95, 98, and Me) to create a file with the correct format. To initially set up your machine if you are a local user, you'd do something like this:

Example 3.7. Setting up the groups file for local accounts

$ mkdir /etc
$ mkgroup -l > /etc/group

Note that this information is static. If you change the group information in your system, you'll need to regenerate the group file for it to have the new information.

The -d and -l options allow you to specify where the information comes from, the local machine or the domain (default or given), or both. With the -d option the program contacts the Domain Controller, which my be unreachable or have restricted access. An entry for the current domain user can then be created by using the option -c together with -l, but -c has no effect when used with -d. The -o option allows for special cases (such as multiple domains) where the GIDs might match otherwise. The -s option omits the NT Security Identifier (SID). For more information on SIDs, see the section called “NT security and usage of ntsec” in the Cygwin User's Guide. The -u option causes mkgroup to enumerate the users for each group, placing the group members in the gr_mem (last) field. Note that this can greatly increase the time for mkgroup to run in a large domain. Having gr_mem fields is helpful when a domain user logs in remotely while the local machine is disconnected from the Domain Controller. The -g option only prints the information for one group.


Usage: mkpasswd [OPTION]... [domain]...
Prints /etc/passwd file to stdout

   -l,--local              print local user accounts
   -c,--current            print current account, if a domain account
   -d,--domain             print domain accounts (from current domain
                           if no domains specified)
   -o,--id-offset offset   change the default offset (10000) added to uids
                           in domain accounts.
   -g,--local-groups       print local group information too
                           if no domains specified
   -m,--no-mount           don't use mount points for home dir
   -s,--no-sids            don't print SIDs in GCOS field
                           (this affects ntsec)
   -p,--path-to-home path  use specified path and not user account home dir or /home
   -u,--username username  only return information for the specified user
   -h,--help               displays this message
   -v,--version            version information and exit

One of `-l', `-d' or `-g' must be given on NT/W2K.

The mkpasswd program can be used to help configure your Windows system to be more UNIX-like by creating an initial /etc/passwd from your system information. Its use is essential on the NT series (Windows NT, 2000, and XP) to include Windows security information, but the actual passwords are determined by Windows, not by the content of /etc/passwd. On the Win9x series (Windows 95, 98, and Me) the password field must be replaced by the output of crypt your_password if remote access is desired. To initially set up your machine if you are a local user, you'd do something like this:

Example 3.8. Setting up the passwd file for local accounts

$ mkdir /etc
$ mkpasswd -l > /etc/passwd

Note that this information is static. If you change the user information in your system, you'll need to regenerate the passwd file for it to have the new information.

The -d and -l options allow you to specify where the information comes from, the local machine or the domain (default or given), or both. With the -d option the program contacts the Domain Controller, which my be unreachable or have restricted access. An entry for the current domain user can then be created by using the option -c together with -l, but -c has no effect when used with -d. The -o option allows for special cases (such as multiple domains) where the UIDs might match otherwise. The -g option creates a local user that corresponds to each local group. This is because NT assigns groups file ownership. The -m option bypasses the current mount table so that, for example, two users who have a Windows home directory of H: could mount them differently. The -s option omits the NT Security Identifier (SID). For more information on SIDs, see the section called “NT security and usage of ntsec” in the Cygwin User's Guide. The -p option causes mkpasswd to use the specified prefix instead of the account home dir or /home/ . For example, this command:

Example 3.9. Using an alternate home root

$ mkpasswd -l -p "$(cygpath -H)" > /etc/passwd

would put local users' home directories in the Windows 'Profiles' directory. On Win9x machines the -u option creates an entry for the specified user. On the NT series it restricts the output to that user, greatly reducing the amount of time it takes in a large domain.


Usage: mount [OPTION] [<win32path> <posixpath>]
Display information about mounted filesystems, or mount a filesystem

  -b, --binary     (default)    text files are equivalent to binary files
                                (newline = \n)
  -c, --change-cygdrive-prefix  change the cygdrive path prefix to <posixpath>
  -f, --force                   force mount, don't warn about missing mount
                                point directories
  -h, --help                    output usage information and exit
  -m, --mount-commands          write mount commands to replicate user and
                                system mount points and cygdrive prefixes
  -o, --options X[,X...]        specify mount options
  -p, --show-cygdrive-prefix    show user and/or system cygdrive path prefix
  -s, --system     (default)    add system-wide mount point
  -t, --text                    text files get \r\n line endings
  -u, --user                    add user-only mount point
  -v, --version                 output version information and exit
  -x, --executable              treat all files under mount point as executables
  -E, --no-executable           treat all files under mount point as 
  -X, --cygwin-executable       treat all files under mount point as cygwin

The mount program is used to map your drives and shares onto Cygwin's simulated POSIX directory tree, much like as is done by mount commands on typical UNIX systems. Please see the section called “The Cygwin Mount Table” for more information on the concepts behind the Cygwin POSIX file system and strategies for using mounts. To remove mounts, use umount

Using mount

If you just type mount with no parameters, it will display the current mount table for you.

Example 3.10. Displaying the current set of mount points

c:\cygwin\> mount
c:\cygwin\bin on /usr/bin type system (binmode)
c:\cygwin\lib on /usr/lib type system (binmode)
c:\cygwin on / type system (binmode)
c: on /c type user (binmode,noumount)
d: on /d type user (binmode,noumount)

In this example, c:\cygwin is the POSIX root and D drive is mapped to /d. Note that in this case, the root mount is a system-wide mount point that is visible to all users running Cygwin programs, whereas the /d mount is only visible to the current user.

The mount utility is also the mechanism for adding new mounts to the mount table. The following example demonstrates how to mount the directory \\pollux\home\joe\data to /data.

Example 3.11. Adding mount points

c:\cygwin\> ls /data
ls: /data: No such file or directory
c:\cygwin\> mount \\pollux\home\joe\data /data
mount: warning - /data does not exist!
c:\cygwin\> mount
\\pollux\home\joe\data on /data type sytem (binmode)
c:\cygwin\bin on /usr/bin type system (binmode)
c:\cygwin\lib on /usr/lib type system (binmode)
c:\cygwin on / type system (binmode)
c: on /c type user (binmode,noumount)
d: on /d type user (binmode,noumount)

Note that mount was invoked from the Windows command shell in the previous example. In many Unix shells, including bash, it is legal and convenient to use the forward "/" in Win32 pathnames since the "\" is the shell's escape character.

The -s flag to mount is used to add a mount in the system-wide mount table used by all Cygwin users on the system, instead of the user-specific one. System-wide mounts are displayed by mount as being of the "system" type, as is the case for the / partition in the last example. Under Windows NT, only those users with Administrator priviledges are permitted to modify the system-wide mount table.

Note that a given POSIX path may only exist once in the user table and once in the global, system-wide table. Attempts to replace the mount will fail with a busy error. The -f (force) flag causes the old mount to be silently replaced with the new one. It will also silence warnings about the non-existence of directories at the Win32 path location.

The -b flag is used to instruct Cygwin to treat binary and text files in the same manner by default. Binary mode mounts are marked as "binmode" in the Flags column of mount output. By default, mounts are in text mode ("textmode" in the Flags column).

Normally, files ending in certain extensions (.exe, .com, .bat, .cmd) are assumed to be executable. Files whose first two characters begin with '#!' are also considered to be executable. The -x flag is used to instruct Cygwin that the mounted file is "executable". If the -x flag is used with a directory then all files in the directory are executable. This option allows other files to be marked as executable and avoids the overhead of opening each file to check for a '#!'. The -X option is very similar to -x, but also prevents Cygwin from setting up commands and environment variables for a normal Windows program, adding another small performance gain. The opposite of these flags is the -E flag, which means that no files should be marked as executable.

The -m option causes the mount utility to output a series of commands that could recreate both user and system mount points. You can save this output as a backup when experimenting with the mount table. It also makes moving your settings to a different machine much easier.

The -o option is the method via which various options about the mount point may be recorded. The following options are available (note that most of the options are duplicates of other mount flags):

  user       - mount lives user-specific mount
  system     - mount lives in system table (default)
  binary     - files default to binary mode (default)
  text       - files default to CRLF text mode line endings
  exec       - files below mount point are all executable
  notexec    - files below mount point are not executable
  cygexec    - files below mount point are all cygwin executables
  nosuid     - no suid files are allowed (currently unimplemented)
  managed    - directory is managed by cygwin.  Mixed case and special
               characters in filenames are allowed.

Cygdrive mount points

Whenever Cygwin cannot use any of the existing mounts to convert from a particular Win32 path to a POSIX one, Cygwin will, instead, convert to a POSIX path using a default mount point: /cygdrive. For example, if Cygwin accesses z:\foo and the z drive is not currently in the mount table, then z:\ will be accessible as /cygdrive/z. The mount utility can be used to change this default automount prefix through the use of the "--change-cygdrive-prefix" option. In the following example, we will set the automount prefix to /:

Example 3.12. Changing the default prefix

c:\cygwin\> mount --change-cygdrive-prefix /

Note that the cygdrive prefix can be set both per-user and system-wide, and that as with all mounts, a user-specific mount takes precedence over the system-wide setting. The mount utility creates system-wide mounts by default if you do not specify a type. Use the -s or -u flag to indicate a system or user mount, respectively. You can always see the user and system cygdrive prefixes with the -p option. Using the -b flag with --change-cygdrive-prefix makes all new automounted filesystems default to binary mode file accesses.


Limitations: there is a hard-coded limit of 30 mount points. Also, although you can mount to pathnames that do not start with "/", there is no way to make use of such mount points.

Normally the POSIX mount point in Cygwin is an existing empty directory, as in standard UNIX. If this is the case, or if there is a place-holder for the mount point (such as a file, a symbolic link pointing anywhere, or a non-empty directory), you will get the expected behavior. Files present in a mount point directory before the mount become invisible to Cygwin programs.

It is sometimes desirable to mount to a non-existent directory, for example to avoid cluttering the root directory with names such as a, b, c pointing to disks. Although mount will give you a warning, most everything will work properly when you refer to the mount point explicitly. Some strange effects can occur however. For example if your current working directory is /dir, say, and /dir/mtpt is a mount point, then mtpt will not show up in an ls or echo * command and find . will not find mtpt.


Usage: passwd [OPTION] [USER]
Change USER's password or password attributes.

User operations:
  -l, --lock               lock USER's account.
  -u, --unlock             unlock USER's account.
  -c, --cannot-change      USER can't change password.
  -C, --can-change         USER can change password.
  -e, --never-expires      USER's password never expires.
  -E, --expires            USER's password expires according to system's
                           password aging rule.
  -p, --pwd-not-required   no password required for USER.
  -P, --pwd-required       password is required for USER.

System operations:
  -i, --inactive NUM       set NUM of days before inactive accounts are disabled
                           (inactive accounts are those with expired passwords).
  -n, --minage DAYS        set system minimum password age to DAYS days.
  -x, --maxage DAYS        set system maximum password age to DAYS days.
  -L, --length LEN         set system minimum password length to LEN.

Other options:
  -S, --status             display password status for USER (locked, expired,
                           etc.) plus global system password settings.
  -h, --help               output usage information and exit.
  -v, --version            output version information and exit.

If no option is given, change USER's password.  If no user name is given,
operate on current user.  System operations must not be mixed with user
operations.  Don't specify a USER when triggering a system operation. 

passwd changes passwords for user accounts. A normal user may only change the password for their own account, but administrators may change passwords on any account. passwd also changes account information, such as password expiry dates and intervals.

For password changes, the user is first prompted for their old password, if one is present. This password is then encrypted and compared against the stored password. The user has only one chance to enter the correct password. The administrators are permitted to bypass this step so that forgotten passwords may be changed.

The user is then prompted for a replacement password. passwd will prompt twice for this replacement and compare the second entry against the first. Both entries are required to match in order for the password to be changed.

After the password has been entered, password aging information is checked to see if the user is permitted to change their password at this time. If not, passwd refuses to change the password and exits.

To get current password status information, use the -S option. Administrators can use passwd to perform several account maintenance functions (users may perform some of these functions on their own accounts). Accounts may be locked with the -l flag and unlocked with the -u flag. Similarly, -c disables a user's ability to change passwords, and -C allows a user to change passwords. For password expiry, the -e option disables expiration, while the -E option causes the password to expire according to the system's normal aging rules. Use -p to disable the password requirement for a user, or -P to require a password.

Administrators can also use passwd to change system-wide password expiry and length requirements with the -i, -n, -x, and -L options. The -i option is used to disable an account after the password has been expired for a number of days. After a user account has had an expired password for NUM days, the user may no longer sign on to the account. The -n option is used to set the minimum number of days before a password may be changed. The user will not be permitted to change the password until MINDAYS days have elapsed. The -x option is used to set the maximum number of days a password remains valid. After MAXDAYS days, the password is required to be changed. Allowed values for the above options are 0 to 999. The -L option sets the minimum length of allowed passwords for users who don't belong to the administrators group to LEN characters. Allowed values for the minimum password length are 0 to 14. In any of the above cases, a value of 0 means `no restrictions'.

Limitations: Users may not be able to change their password on some systems.


Usage: ps [-aefls] [-u UID]
Report process status

 -a, --all       show processes of all users
 -e, --everyone  show processes of all users
 -f, --full      show process uids, ppids
 -h, --help      output usage information and exit
 -l, --long      show process uids, ppids, pgids, winpids
 -p, --process   show information for specified PID
 -s, --summary   show process summary
 -u, --user      list processes owned by UID
 -v, --version   output version information and exit
 -W, --windows   show windows as well as cygwin processes
With no options, ps outputs the long format by default

The ps program gives the status of all the Cygwin processes running on the system (ps = "process status"). Due to the limitations of simulating a POSIX environment under Windows, there is little information to give.

The PID column is the process ID you need to give to the kill command. The PPID is the parent process ID, and PGID is the process group ID. The WINPID column is the process ID displayed by NT's Task Manager program. The TTY column gives which pseudo-terminal a process is running on, or a '?' for services. The UID column shows which user owns each process. STIME is the time the process was started, and COMMAND gives the name of the program running. Listings may also have a status flag in column zero; S means stopped or suspended (in other words, in the background), I means waiting for input or interactive (foreground), and O means waiting to output.

By default ps will only show processes owned by the current user. With either the -a or -e option, all user's processes (and system processes) are listed. There are historical UNIX reasons for the synonomous options, which are functionally identical. The -f option outputs a "full" listing with usernames for UIDs. The -l option is the default display mode, showing a "long" listing with all the above columns. The other display option is -s, which outputs a shorter listing of just PID, TTY, STIME, and COMMAND. The -u option allows you to show only processes owned by a specific user. The -p option allows you to show information for only the process with the specified PID. The -W option causes ps show non-Cygwin Windows processes as well as Cygwin processes. The WINPID is also the PID, and they can be killed with the Cygwin kill command's -f option.


Usage: regtool [OPTION] (add|check|get|list|remove|unset|load|unload|save) KEY
View or edit the Win32 registry

 add KEY\SUBKEY             add new SUBKEY
 check KEY                  exit 0 if KEY exists, 1 if not
 get KEY\VALUE              prints VALUE to stdout
 list KEY                   list SUBKEYs and VALUEs
 remove KEY                 remove KEY
 set KEY\VALUE [data ...]   set VALUE
 unset KEY\VALUE            removes VALUE from KEY
 load KEY\SUBKEY PATH       load hive from PATH into new SUBKEY
 unload KEY\SUBKEY          unload hive and remove SUBKEY
 save KEY\SUBKEY PATH       save SUBKEY into new hive PATH

Options for 'list' Action:
 -k, --keys           print only KEYs
 -l, --list           print only VALUEs
 -p, --postfix        like ls -p, appends '\' postfix to KEY names

Options for 'get' Action:
 -b, --binary         print REG_BINARY data as hex bytes

Options for 'set' Action:
 -b, --binary         set type to REG_BINARY (hex args or '-')
 -e, --expand-string  set type to REG_EXPAND_SZ
 -i, --integer        set type to REG_DWORD
 -m, --multi-string   set type to REG_MULTI_SZ
 -s, --string         set type to REG_SZ

Options for 'set' and 'unset' Actions:
 -K<c>, --key-separator[=]<c>  set key separator to <c> instead of '\'

Other Options:
 -h, --help     output usage information and exit
 -q, --quiet    no error output, just nonzero return if KEY/VALUE missing
 -v, --verbose  verbose output, including VALUE contents when applicable
 -V, --version  output version information and exit

KEY is in the format [host]\prefix\KEY\KEY\VALUE, where host is optional
remote host in either \\hostname or hostname: format and prefix is any of:
  root     HKCR  HKEY_CLASSES_ROOT (local only)
  config   HKCC  HKEY_CURRENT_CONFIG (local only)
  user     HKCU  HKEY_CURRENT_USER (local only)
  users    HKU   HKEY_USERS

You can use forward slash ('/') as a separator instead of backslash, in
that case backslash is treated as escape character
Example: regtool.exe get '\user\software\Microsoft\Clock\iFormat'

The regtool program allows shell scripts to access and modify the Windows registry. Note that modifying the Windows registry is dangerous, and carelessness here can result in an unusable system. Be careful.

The -v option means "verbose". For most commands, this causes additional or lengthier messages to be printed. Conversely, the -q option supresses error messages, so you can use the exit status of the program to detect if a key exists or not (for example).

You must provide regtool with an action following options (if any). Currently, the action must be add, set, check, get, list, remove, set, or unset.

The add action adds a new key. The check action checks to see if a key exists (the exit code of the program is zero if it does, nonzero if it does not). The get action gets the value of a value of a key, and prints it (and nothing else) to stdout. Note: if the value doesn't exist, an error message is printed and the program returns a non-zero exit code. If you give -q, it doesn't print the message but does return the non-zero exit code.

The list action lists the subkeys and values belonging to the given key. With list, the -k option instructs regtool to print only KEYs, and the -l option to print only VALUEs. The -p option postfixes a '/' to each KEY, but leave VALUEs with no postfix. The remove action removes a key. Note that you may need to remove everything in the key before you may remove it, but don't rely on this stopping you from accidentally removing too much.

The set action sets a value within a key. -b means it's binary data (REG_BINARY). The binary values are specified as hex bytes in the argument list. If the argument is '-', binary data is read from stdin instead. -e means it's an expanding string (REG_EXPAND_SZ) that contains embedded environment variables. -i means the value is an integer (REG_DWORD). -m means it's a multi-string (REG_MULTI_SZ). -s means the value is a string (REG_SZ). If you don't specify one of these, regtool tries to guess the type based on the value you give. If it looks like a number, it's a DWORD. If it starts with a percent, it's an expanding string. If you give multiple values, it's a multi-string. Else, it's a regular string. The unset action removes a value from a key.

The load action adds a new subkey and loads the contents of a registry hive into it. The parent key must be HKEY_LOCAL_MACHINE or HKEY_USERS. The unload action unloads the file and removes the subkey.

The save action saves a subkey into a registry hive.

By default, the last "\" or "/" is assumed to be the separator between the key and the value. You can use the -K option to provide an alternate key/value separator character.


Usage: setfacl [-r] (-f ACL_FILE | -s acl_entries) FILE...
       setfacl [-r] ([-d acl_entries] [-m acl_entries]) FILE...
Modify file and directory access control lists (ACLs)

  -d, --delete     delete one or more specified ACL entries
  -f, --file       set ACL entries for FILE to ACL entries read
                   from a ACL_FILE
  -m, --modify     modify one or more specified ACL entries
  -r, --replace    replace mask entry with maximum permissions
                   needed for the file group class
  -s, --substitute substitute specified ACL entries for the
                   ACL of FILE
  -h, --help       output usage information and exit
  -v, --version    output version information and exit

At least one of (-d, -f, -m, -s) must be specified

For each file given as parameter, setfacl will either replace its complete ACL (-s, -f), or it will add, modify, or delete ACL entries. For more information on Cygwin and Windows ACLs, see see the section called “NT security and usage of ntsec” in the Cygwin User's Guide.

Acl_entries are one or more comma-separated ACL entries from the following list:


Default entries are like the above with the additional default identifier. For example:


perm is either a 3-char permissions string in the form "rwx" with the character '-' for no permission or it is the octal representation of the permissions, a value from 0 (equivalent to "---") to 7 ("rwx"). uid is a user name or a numerical uid. gid is a group name or a numerical gid.

The following options are supported:

-d Delete one or more specified entries from the file's ACL. The owner, group and others entries must not be deleted. Acl_entries to be deleted should be specified without permissions, as in the following list:


-f Take the Acl_entries from ACL_FILE one per line. Whitespace characters are ignored, and the character "#" may be used to start a comment. The special filename "-" indicates reading from stdin. Note that you can use this with getfacl and setfacl to copy ACLs from one file to another:

$ getfacl source_file | setfacl -f - target_file

Required entries are: one user entry for the owner of the file, one group entry for the group of the file, and one other entry.

If additional user and group entries are given: a mask entry for the file group class of the file, and no duplicate user or group entries with the same uid/gid.

If it is a directory: one default user entry for the owner of the file, one default group entry for the group of the file, one default mask entry for the file group class, and one default other entry.

-m Add or modify one or more specified ACL entries. Acl_entries is a comma-separated list of entries from the same list as above.

-r Causes the permissions specified in the mask entry to be ignored and replaced by the maximum permissions needed for the file group class.

-s Like -f, but substitute the file's ACL with Acl_entries specified in a comma-separated list on the command line.

While the -d and -m options may be used in the same command, the -f and -s options may be used only exclusively.

Directories may contain default ACL entries. Files created in a directory that contains default ACL entries will have permissions according to the combination of the current umask, the explicit permissions requested and the default ACL entries

Limitations: Under Cygwin, the default ACL entries are not taken into account currently.


Usage: ssp [options] low_pc high_pc command...
Single-step profile COMMAND

 -c, --console-trace  trace every EIP value to the console. *Lots* slower.
 -d, --disable        disable single-stepping by default; use
                      OutputDebugString ("ssp on") to enable stepping
 -e, --enable         enable single-stepping by default; use
                      OutputDebugString ("ssp off") to disable stepping
 -h, --help           output usage information and exit
 -l, --dll            enable dll profiling.  A chart of relative DLL usage
                      is produced after the run.
 -s, --sub-threads    trace sub-threads too.  Dangerous if you have
                      race conditions.
 -t, --trace-eip      trace every EIP value to a file TRACE.SSP.  This
                      gets big *fast*.
 -v, --verbose        output verbose messages about debug events.
 -V, --version        output version information and exit

Example: ssp 0x401000 0x403000 hello.exe

SSP - The Single Step Profiler

Original Author: DJ Delorie

The SSP is a program that uses the Win32 debug API to run a program one ASM instruction at a time. It records the location of each instruction used, how many times that instruction is used, and all function calls. The results are saved in a format that is usable by the profiling program gprof, although gprof will claim the values are seconds, they really are instruction counts. More on that later.

Because the SSP was originally designed to profile the cygwin DLL, it does not automatically select a block of code to report statistics on. You must specify the range of memory addresses to keep track of manually, but it's not hard to figure out what to specify. Use the "objdump" program to determine the bounds of the target's ".text" section. Let's say we're profiling cygwin1.dll. Make sure you've built it with debug symbols (else gprof won't run) and run objdump like this:

$ objdump -h cygwin1.dll

It will print a report like this:

cygwin1.dll:     file format pei-i386

Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         0007ea00  61001000  61001000  00000400  2**2
  1 .data         00008000  61080000  61080000  0007ee00  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  . . .

The only information we're concerned with are the VMA of the .text section and the VMA of the section after it (sections are usually contiguous; you can also add the Size to the VMA to get the end address). In this case, the VMA is 0x61001000 and the ending address is either 0x61080000 (start of .data method) or 0x0x6107fa00 (VMA+Size method).

There are two basic ways to use SSP - either profiling a whole program, or selectively profiling parts of the program.

To profile a whole program, just run ssp without options. By default, it will step the whole program. Here's a simple example, using the numbers above:

$ ssp 0x61001000 0x61080000 hello.exe

This will step the whole program. It will take at least 8 minutes on a PII/300 (yes, really). When it's done, it will create a file called "gmon.out". You can turn this data file into a readable report with gprof:

$ gprof -b cygwin1.dll

The "-b" means 'skip the help pages'. You can omit this until you're familiar with the report layout. The gprof documentation explains a lot about this report, but ssp changes a few things. For example, the first part of the report reports the amount of time spent in each function, like this:

Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total
 time   seconds   seconds    calls  ms/call  ms/call  name
 10.02    231.22    72.43       46  1574.57  1574.57  strcspn
  7.95    288.70    57.48      130   442.15   442.15  strncasematch

The "seconds" columns are really CPU opcodes, 1/100 second per opcode. So, "231.22" above means 23,122 opcodes. The ms/call values are 10x too big; 1574.57 means 157.457 opcodes per call. Similar adjustments need to be made for the "self" and "children" columns in the second part of the report.

OK, so now we've got a huge report that took a long time to generate, and we've identified a spot we want to work on optimizing. Let's say it's the time() function. We can use SSP to selectively profile this function by using OutputDebugString() to control SSP from within the program. Here's a sample program:

	#include <windows.h>
	  time_t t;
	  OutputDebugString("ssp on");
	  OutputDebugString("ssp off");

Then, add the -d option to ssp to default to *disabling* profiling. The program will run at full speed until the first OutputDebugString, then step until the second. You can then use gprof (as usual) to see the performance profile for just that portion of the program's execution.

There are many options to ssp. Since step-profiling makes your program run about 1,000 times slower than normal, it's best to understand all the options so that you can narrow down the parts of your program you need to single-step.

-v - verbose. This prints messages about threads starting and stopping, OutputDebugString calls, DLLs loading, etc.

-t and -c - tracing. With -t, *every* step's address is written to the file "trace.ssp". This can be used to help debug functions, since it can trace multiple threads. Clever use of scripts can match addresses with disassembled opcodes if needed. Warning: creates *huge* files, very quickly. -c prints each address to the console, useful for debugging key chunks of assembler. Use addr2line -C -f -s -e foo.exe < trace.ssp > lines.ssp and then perl cvttrace to convert to symbolic traces.

-s - subthreads. Usually, you only need to trace the main thread, but sometimes you need to trace all threads, so this enables that. It's also needed when you want to profile a function that only a subthread calls. However, using OutputDebugString automatically enables profiling on the thread that called it, not the main thread.

-l - dll profiling. Generates a pretty table of how much time was spent in each dll the program used. No sense optimizing a function in your program if most of the time is spent in the DLL. I usually use the -v, -s, and -l options:

$ ssp -v -s -l -d 0x61001000 0x61080000 hello.exe


Usage: strace.exe [OPTIONS] <command-line>
Usage: strace.exe [OPTIONS] -p <pid>
Trace system calls and signals

  -b, --buffer-size=SIZE       set size of output file buffer
  -d, --no-delta               don't display the delta-t microsecond timestamp
  -f, --trace-children         trace child processes (toggle - default true)
  -h, --help                   output usage information and exit
  -m, --mask=MASK              set message filter mask
  -n, --crack-error-numbers    output descriptive text instead of error
                               numbers for Windows errors
  -o, --output=FILENAME        set output file to FILENAME
  -p, --pid=n                  attach to executing program with cygwin pid n
  -q, --quiet                  toggle "quiet" flag.  Defaults to on if "-p",
                               off otherwise.
  -S, --flush-period=PERIOD    flush buffered strace output every PERIOD secs
  -t, --timestamp              use an absolute hh:mm:ss timestamp insted of 
                               the default microsecond timestamp.  Implies -d
  -T, --toggle                 toggle tracing in a process already being
  -u, --usecs                  toggle printing of microseconds timestamp
                               traced. Requires -p <pid>
  -v, --version                output version information and exit
  -w, --new-window             spawn program under test in a new window

    MASK can be any combination of the following mnemonics and/or hex values
    (0x is optional).  Combine masks with '+' or ',' like so:


    Mnemonic Hex     Corresponding Def  Description
    all      0x00001 (_STRACE_ALL)      All strace messages.
    flush    0x00002 (_STRACE_FLUSH)    Flush output buffer after each message.
    inherit  0x00004 (_STRACE_INHERIT)  Children inherit mask from parent.
    uhoh     0x00008 (_STRACE_UHOH)     Unusual or weird phenomenon.
    syscall  0x00010 (_STRACE_SYSCALL)  System calls.
    startup  0x00020 (_STRACE_STARTUP)  argc/envp printout at startup.
    debug    0x00040 (_STRACE_DEBUG)    Info to help debugging. 
    paranoid 0x00080 (_STRACE_PARANOID) Paranoid info.
    termios  0x00100 (_STRACE_TERMIOS)  Info for debugging termios stuff.
    select   0x00200 (_STRACE_SELECT)   Info on ugly select internals.
    wm       0x00400 (_STRACE_WM)       Trace Windows msgs (enable _strace_wm).
    sigp     0x00800 (_STRACE_SIGP)     Trace signal and process handling.
    minimal  0x01000 (_STRACE_MINIMAL)  Very minimal strace output.
    exitdump 0x04000 (_STRACE_EXITDUMP) Dump strace cache on exit.
    system   0x08000 (_STRACE_SYSTEM)   Serious error; goes to console and log.
    nomutex  0x10000 (_STRACE_NOMUTEX)  Don't use mutex for synchronization.
    malloc   0x20000 (_STRACE_MALLOC)   Trace malloc calls.
    thread   0x40000 (_STRACE_THREAD)   Thread-locking calls.

The strace program executes a program, and optionally the children of the program, reporting any Cygwin DLL output from the program(s) to stdout, or to a file with the -o option. With the -w option, you can start an strace session in a new window, for example:

$ strace -o tracing_output -w sh -c 'while true; do echo "tracing..."; done' &

This is particularly useful for strace sessions that take a long time to complete.

Note that strace is a standalone Windows program and so does not rely on the Cygwin DLL itself (you can verify this with cygcheck). As a result it does not understand symlinks. This program is mainly useful for debugging the Cygwin DLL itself.


Usage: umount.exe [OPTION] [<posixpath>]
Unmount filesystems

  -A, --remove-all-mounts       remove all mounts
  -c, --remove-cygdrive-prefix  remove cygdrive prefix
  -h, --help                    output usage information and exit
  -s, --system                  remove system mount (default)
  -S, --remove-system-mounts    remove all system mounts
  -u, --user                    remove user mount
  -U, --remove-user-mounts      remove all user mounts
  -v, --version                 output version information and exit

The umount program removes mounts from the mount table. If you specify a POSIX path that corresponds to a current mount point, umount will remove it from the system registry area. (Administrator priviledges are required). The -u flag may be used to specify removing the mount from the user-specific registry area instead.

The umount utility may also be used to remove all mounts of a particular type. With the extended options it is possible to remove all mounts (-A), all cygdrive automatically-mounted mounts (-c), all mounts in the current user's registry area (-U), or all mounts in the system-wide registry area (-S) (with Administrator privileges).

See the section called “mount” for more information on the mount table.