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• Typical Unix shells (bash, etc.) have no built-in registry of file types and associated default applications. Linux command-line tools with similar functions include xdg-open^[8] and run-mailcap.
• On Cygwin, the command is implemented as the cygstart executable.^[9]
• In PowerShell, the Invoke-Item cmdlet is used to invoke an executable or open a file.^[10]
• On Apple macOS, the corresponding command is open.
• On Stratus OpenVOS it is start_process.^[11]

start "title" [/D path] [options] "command" [parameters]

• Kathy Ivens; Brian Proffit (1993). OS/2 Inside & Out. Osborne McGraw-Hill. ISBN 978-0078818714.
• Frisch, Æleen (2001). Windows 2000 Commands Pocket Reference. O’Reilly. ISBN 978-0-596-00148-3.

A batch file is a script file in DOS, OS/2 and Microsoft Windows. It consists of a series of commands to be executed by the command-line interpreter, stored in a plain text file. A batch file may contain any command the interpreter accepts interactively and use constructs that enable conditional branching and looping within the batch file, such as IF, FOR, and GOTO labels. The term “batch” is from batch processing, meaning “non-interactive execution”, though a batch file might not process a batch of multiple data.

The filename extension .bat is used in DOS and Windows. Windows NT and OS/2 also added .cmd. Batch files for other environments may have different extensions, e.g., .btm in 4DOS, 4OS2 and 4NT related shells.

The detailed handling of batch files has changed significantly between versions. Some of the detail in this article applies to all batch files, while other details apply only to certain versions.

A .bat file name extension identifies a file containing commands that are executed by the command interpreter COMMAND.COM line by line, as if it were a list of commands entered manually, with some extra batch-file-specific commands for basic programming functionality, including a GOTO command for changing flow of line execution.

The IBM OS/2 operating system supported DOS-style batch files. It also included a version of REXX, a more advanced batch-file scripting language. IBM and Microsoft started developing this system, but during the construction of it broke up after a dispute; as a result of this, IBM referred to their DOS-like console shell without mention of Microsoft, naming it just DOS, although this seemingly made no difference with regard to the way batch files worked from COMMAND.COM.

OS/2’s batch file interpreter also supports an EXTPROC command. This passes the batch file to the program named on the EXTPROC file as a data file. The named program can be a script file; this is similar to the #! mechanism used by Unix-like operating systems.

Unlike Windows 98 and earlier, the Windows NT family of operating systems does not depend on MS-DOS. Windows NT introduced an enhanced 32-bit command interpreter (cmd.exe) that could execute scripts with either the .CMD or .BAT extension. Cmd.exe added additional commands, and implemented existing ones in a slightly different way, so that the same batch file (with different extension) might work differently with cmd.exe and COMMAND.COM. In most cases, operation is identical if the few unsupported commands are not used. Cmd.exe’s extensions to COMMAND.COM can be disabled for compatibility.

.bat

The first filename extension used by Microsoft for batch files. This extension runs with DOS and all versions of Windows, under COMMAND.COM or cmd.exe, despite the different ways the two command interpreters execute batch files.

.cmd

Used for batch files in Windows NT family and sent to cmd.exe for interpretation. COMMAND.COM does not recognize this file name extension, so cmd.exe scripts are not executed in the wrong Windows environment by mistake. In addition, append, dpath, ftype, set, path, assoc and prompt commands, when executed from a .bat file, alter the value of the errorlevel variable only upon an error, whereas from within a .cmd file, they would affect errorlevel even when returning without an error.^[3] It is also used by IBM’s OS/2 for batch files.

.btm

The extension used by 4DOS, 4OS2, 4NT and Take Command. These scripts are faster, especially with longer ones, as the script is loaded entirely ready for execution, rather than line-by-line.^[4]

 OFF Hello World!

To execute the file, it must be saved with the filename extension suffix .bat (or .cmd for Windows NT-type operating systems) in plain text format, typically created by using a text editor such as Microsoft Notepad or a word processor working in plain text mode.

Hello World!
Press any key to continue . . .

Null values in variables

Variable expansions are substituted textually into the command, and thus variables which contain nothing simply disappear from the syntax, and variables which contain spaces turn into multiple tokens. This can lead to syntax errors or bugs.

For example, if %foo% is empty, this statement:

parses as the erroneous construct:

Similarly, if %foo% contains abc def, then a different syntax error results:

 abcbar Equal

The usual way to prevent this problem is to surround variable expansions in quotes so that an empty variable expands into the valid expression IF ""=="bar" instead of the invalid IF ==bar. The text that is being compared to the variable must also be enclosed in quotes, because the quotes are not special delimiting syntax; these characters represent themselves.

 Equal

The delayed !VARIABLE! expansion available in Windows 2000 and later may be used to avoid these syntactical errors. In this case, null or multi-word variables do not fail syntactically because the value is expanded after the IF command is parsed:

Another difference in Windows 2000 or higher is that an empty variable (undefined) is not substituted. As described in previous examples, previous batch interpreter behaviour would have resulted in an empty string. Example:

 MyVar is not defined MyVar is MyVar is %MyVar%

Batch interpreters prior to Windows 2000 would have displayed result MyVar is not defined.

Quotation marks and spaces in passed strings

Unlike Unix/POSIX processes, which receive their command-line arguments already split up by the shell into an array of strings, a Windows process receives the entire command-line as a single string, via the GetCommandLine API function. As a result, each Windows application can implement its own parser to split the entire command line into arguments. Many applications and command-line tools have evolved their own syntax for doing that, and so there is no single convention for quoting or escaping metacharacters on Windows command lines.

• For some commands, spaces are treated as delimiters that separate arguments, unless those spaces are enclosed by quotation marks. Various conventions exist of how quotation marks can be passed on to the application:
  • A widely used convention is implemented by the command-line parser built into the Microsoft Visual C++ runtime library in the CommandLineToArgvW function. It uses the convention that 2n backslashes followed by a quotation mark (“) produce n backslashes followed by a begin/end quote, whereas (2n)+1 backslashes followed by a quotation mark again produce n backslashes followed by a quotation mark literal. The same convention is part of the .NET Framework specification.^[7]
    • An undocumented aspect is that occurring in the middle of a quoted string produces a single quotation mark.^[7] (A CRT change in 2008 [msvcr90] modified this undocumented handling of quotes.^[8]) This is helpful for inserting a quotation mark in an argument without re-enabling interpretation of cmd metacharacters like , and . (cmd does not recognize the usual as escaping the quote. It re-enables these special meanings on seeing the quote, thinking the quotation has ended.)
  • Another convention is that a single quotation mark () is not included as part of the string. However, an escaped quotation mark () can be part of the string.^[]
  • Yet another common convention comes from the use of Cygwin-derived ported programs. It does not differentiate between backslashes occurring before or not before quotes. See glob (programming) § Windows and DOS for information on these alternative command-line parsers.^[9]
  • Some important Windows commands, like cmd.exe and wscript.exe, use their own rules.^[8]
• For other commands, spaces are not treated as delimiters and therefore do not need quotation marks. If quotes are included they become part of the string. This applies to some built-in commands like .

Where a string contains quotation marks, and is to be inserted into another line of text that must also be enclosed in quotation marks, particular attention to the quoting mechanism is required:

 "this string is enclosed in quotation marks" "test 1 "this string is enclosed in quotation marks""eventcreate /T Warning /ID 1 /L System /SO /D ERROR: Invalid Argument/Option - 'string'.Type "EVENTCREATE /?" for usage.

On Windows 2000 and later, the solution is to replace each occurrence of a quote character within a value by a series of three quote characters:

 "this string is enclosed in quotes" "test 1 """this string is enclosed in quotes""""eventcreate /T Warning /ID 1 /L System /SO /D SUCCESS: A 'Warning' type event is created in the 'Source' log/source.

Escaped characters in strings

 foo bar'bar' is not recognized as an internal or external command,operable program or batch file. foo bar

 bar baz'baz' is not recognized as an internal or external command,operable program or batch file. bar bar 'baz' is not recognized as an internal or external command,operable program or batch file. bar baz 

The delayed expansion available with or with in Windows 2000 and later may be used to show special characters stored in environment variables because the variable value is expanded after the command was parsed:

cmd /V:ON bar baz 

Sleep or scripted delay

Until the TIMEOUT command was introduced with Windows Vista, there was no easy way to implement a timed pause, as the PAUSE command halts script activity indefinitely until any key is pressed.

Text output with stripped CR/LF

Normally, all printed text automatically has the control characters for carriage return (CR) and line feed (LF) appended to the end of each line.

• batchtest.bat

  batchtest.bat

 Message 1 Message 2

• batchtest2.bat

   off nul Message 2 Message 3

  batchtest2.batMessage 1Message 2

This can be used to output data to a text file without CR/LF appended to the end:

 nul data.txt nul data.txt nul data.txt data.txtMessage 1Message 2Message 3

However, there is no way to inject this stripped CR/LF prompt output directly into an environment variable.

Setting a Uniform Naming Convention (UNC) working directory from a shortcut

If not enabled by default, command extensions can be temporarily enabled using the /E:ON switch for the command interpreter.

• Target:

The working directory attribute of this shortcut is ignored.

%~dp0

To get a command prompt with Unicode instead of Code page 437 or similar, one can use the cmd /U command. In such a command prompt, a batch file with Unicode filenames will work. Also one can use cmd /U to directly execute commands with Unicode as character set. For example, cmd /U /C dir > files.txt creates a file containing a directory listing with correct Windows characters, in the UTF-16LE encoding.

These three commands are a simple fork bomb that will continually replicate itself to deplete available system resources, slowing down or crashing the system:

There are other, later and more powerful, scripting languages available for Windows. However, these require the scripting language interpreter to be installed before they can be used:

• Extended Batch Language (EBL) (.bat) — developed by Frank Canova as an ‘own-time’ project while working at IBM in 1982. It was subsequently sold by Seaware Corp as an interpreter and compiler primarily for DOS, but later for Windows.
• KiXtart (.kix) — developed by a Microsoft employee in 1991, specifically to meet the need for commands useful in a network logon script while retaining the simple ‘feel’ of a .cmd file.
• Windows Script Host (.vbs , .js and .wsf) — released by Microsoft in 1998, and consisting of cscript.exe and wscript.exe, runs scripts written in VBScript or JScript. It can run them in windowed mode (with the wscript.exe host) or in console-based mode (with the cscript.exe host). They have been a part of Windows since Windows 98.
• PowerShell (.ps1) — released in 2006 by Microsoft and can operate with Windows XP (SP2/SP3) and later versions. PowerShell can operate both interactively (from a command-line interface) and also via saved scripts, and has a strong resemblance to Unix shells.^[15]
• Unix-style shell scripting languages can be used if a Unix compatibility tool, such as Cygwin, is installed.
• Cross-platform scripting tools including Perl, Python, Ruby, Rexx, Node.js and PHP are available for Windows.

• Microsoft Windows XP Batch file reference
• How Windows batch files work
• Windows 10 batch file commands
• FreeDOS’ FreeCOM : complete feature list
• Windows Command Line Interface script programming links
• scripting related information (also command line)
• dbenham. “How does the Windows Command Interpreter (CMD.EXE) parse scripts?”. Stack Overflow.

The Bat! supports POP3, IMAP, and Microsoft Exchange Server email.

The Bat! provides virtual folders, advanced filtering, extensive search, a macro language, templates, tags, and color groups to assist in managing email.

Themes and Customization

In November 2020, with release of version 9.3 The Bat! introduced a number of themes to change its look and feel, also providing the ability for further color changes to the themes as provided. Toolbars and menus may also be modified, although doing that is difficult and not well documented.

• Encryption. The internal PGP implementation based on OpenSSL lets users encrypt messages and sign them with digital signatures. Digital keys manager is included. PGP up to version 10.0.2 is supported. The Bat! supports S/MIME via Internal Implementation or Microsoft CryptoAPI, Secure Socket Layer (SSL) v3.0 / Transport Layer Security (TLS) v1.0, v1.1, and 1.2 (as of version 8.5) with AES algorithm.
• Internal HTML Viewer. The Bat!’s internal viewer was replaced in version 9.2.1 with the Chromium web browser rendering engine to ensure HTML formatting is properly rendered, prevent script execution, and provide anti-phishing information.
• Safe handling of attached files. The Bat! checks attached file extensions and blocks their launching if they are suspicious. The Bat! warns users of double extension attachments and allows users to see the real extension.
• Selective download. Messages can be deleted or left on POP3 servers by setting up respective filters in the Sorting Office.
• OAuth 2.0 Support. The Bat! v9.2.3 is in compliance with the Google’s security standards related to the OAuth 2.0 protocol for authentication with Gmail, Outlook and Yandex. Version 9.3.2 extended support to Office365.com and Live.com
• TLS AEAD AES-GCM cipher suites support. The Bat! v9.1 supports TLS AEAD AES-GCM cipher suites for secure connections with mail servers.

• Sorting Office. A filtering system that sorts incoming, outgoing, read, and replied messages to folders; auto-responds; replies with custom templates; forwards, redirects, prints, or exports messages; sends read confirmations; runs external programs and more.
• Message Templates and Macros. Email templates contents may be dynamically changed through the use of macros, which can also be used to automatically execute other user-defined functions such as cursor positioning, addressing changes, identity changes, active account changes and other.
• Microsoft Exchange Connectivity. The Bat! connects to Microsoft Exchange Server using native MAPI protocol to fetch or send messages.
• Multilingual Interface. Support for 18 languages.
• IDN support. Support for IDNs that contain characters from non-Latin alphabets such as Arabic, Chinese, Cyrillic and Greek. IDN support includes Latin alphabet-based characters with diacritics, such as those found in French and German.