Batch Files to Read Com Port for Scales

Script file for Microsoft figurer operating systems

Batch file

Filename extensions	.bat, .cmd, .btm
Internet media type	application/bat application/x-bat awarding/x-msdos-program text/plain
Type of format	Scripting
Container for	Scripts

A batch file is a script file in DOS, OS/2 and Microsoft Windows. It consists of a serial 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 employ constructs that enable conditional branching and looping within the batch file, such every bit IF, FOR, and GOTO labels. The term "batch" is from batch processing, meaning "non-interactive execution", though a batch file might not procedure a batch of multiple information.

Similar to Job Control Language (JCL), DCL and other systems on mainframe and minicomputer systems, batch files were added to ease the work required for certain regular tasks by allowing the user to prepare a script to automate them. When a batch file is run, the shell programme (usually COMMAND.COM or cmd.exe) reads the file and executes its commands, normally line-by-line.^[one] Unix-like operating systems, such every bit Linux, take a similar, but more flexible, type of file called a shell script.^[2]

The filename extension .bat is used in DOS and Windows. Windows NT and Os/ii too added .cmd. Batch files for other environments may have different extensions, east.g., .btm in 4DOS, 4OS2 and 4NT related shells.

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

Variants [edit]

DOS [edit]

In DOS, a batch file can be started from the command-line interface by typing its name, followed by any required parameters and pressing the ↵ Enter key. When DOS loads, the file AUTOEXEC.BAT, when nowadays, is automatically executed, so any commands that demand to be run to ready the DOS surround may be placed in this file. Computer users would have the AUTOEXEC.BAT file gear up the organisation date and fourth dimension, initialize the DOS environment, load any resident programs or device drivers, or initialize network connections and assignments.

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

Early on Windows [edit]

Microsoft Windows was introduced in 1985 equally a graphical user interface-based (GUI) overlay on text-based operating systems and was designed to run on DOS. In gild to start it, the WIN command was used, which could be added to the finish of the AUTOEXEC.BAT file to allow automatic loading of Windows. In the before versions, one could run a .bat blazon file from Windows in the MS-DOS Prompt. Windows 3.1x and earlier, likewise every bit Windows 9x invoked Control.COM to run batch files.

Os/2 [edit]

The IBM OS/ii operating organisation supported DOS-style batch files. Information technology likewise included a version of REXX, a more avant-garde batch-file scripting linguistic communication. IBM and Microsoft started developing this arrangement, but during the construction of it broke up after a dispute; every bit a result of this, IBM referred to their DOS-like panel trounce without mention of Microsoft, naming it just DOS, although this seemingly made no deviation with regard to the mode batch files worked from Control.COM.

OS/2'due south batch file interpreter also supports an EXTPROC command. This passes the batch file to the plan named on the EXTPROC file as a data file. The named program can be a script file; this is similar to the #! mechanism.

Windows NT [edit]

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 dissimilar way, then that the same batch file (with different extension) might piece of work differently with cmd.exe and COMMAND.COM. In almost cases, operation is identical if the few unsupported commands are not used. Cmd.exe's extensions to COMMAND.COM can be disabled for compatibility.

Microsoft released a version of cmd.exe for Windows 9x and ME chosen WIN95CMD to allow users of older versions of Windows to utilize certain cmd.exe-fashion batch files.

Equally of Windows 8^[update], cmd.exe is the normal command interpreter for batch files; the older Control.COM can exist run as well in 32-flake versions of Windows able to run xvi-scrap programs.^{[nb 1]}

Filename extensions [edit]

.bat

The first filename extension used by Microsoft for batch files. This extension runs with DOS and all versions of Windows, nether COMMAND.COM or cmd.exe, despite the unlike ways the ii 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 surround past mistake. In add-on, 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 fault, whereas from within a .cmd file, they would affect errorlevel even when returning without an error.^[3] Information technology is likewise used by IBM's Bone/2 for batch files.

.btm

The extension used by 4DOS, 4OS2, 4NT and Accept Command. These scripts are faster, particularly with longer ones, equally the script is loaded entirely gear up for execution, rather than line-by-line.^[4]

Batch file parameters [edit]

Control.COM and cmd.exe support special variables (%0, %one through %9) in order to refer to the path and proper noun of the batch job and the first 9 calling parameters from inside the batch job, encounter as well SHIFT. Non-existent parameters are replaced by a zero-length string. They tin exist used similar to environs variables, but are not stored in the environment. Microsoft and IBM refer to these variables every bit replacement parameters or replaceable parameters, whereas Digital Research, Novell and Caldera established the term replacement variables ^[5] for them. JP Software calls them batch file parameters.^[6]

Examples [edit]

This example batch file displays Hullo Globe!, prompts and waits for the user to press a key, so terminates. (Annotation: It does not matter if commands are lowercase or uppercase unless working with variables)

                        @            Echo            OFF            ECHO            Hello Earth!            PAUSE          

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

When executed, the following is displayed:

Hello Globe! Press any key to go on . . .        

Explanation [edit]

The interpreter executes each line in turn, starting with the first. The @ symbol at the start of any line prevents the prompt from displaying that command as it is executed. The command Echo OFF turns off the prompt permanently, or until it is turned on again. The combined @ECHO OFF is ofttimes as hither the starting time line of a batch file, preventing any commands from displaying, itself included. Then the next line is executed and the Echo Hello World! control outputs How-do-you-do World!. The adjacent line is executed and the Interruption command displays Printing any key to continue . . . and pauses the script's execution. Later on a key is pressed, the script terminates, equally there are no more than commands. In Windows, if the script is executed from an already running control prompt window, the window remains open at the prompt as in MS-DOS; otherwise, the window closes on termination.

Limitations and exceptions [edit]

Null values in variables [edit]

Variable expansions are substituted textually into the command, and thus variables which contain naught simply disappear from the syntax, and variables which contain spaces plow into multiple tokens. This tin lead to syntax errors or bugs.

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

parses as the erroneous construct:

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

                        IF            abc              def            ==bar            ECHO            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, considering the quotes are non special delimiting syntax; these characters represent themselves.

                        IF            "            %foo%            "            ==            "bar"            ECHO            Equal          

The delayed !VARIABLE! expansion bachelor in Windows 2000 and later may be used to avoid these syntactical errors. In this case, null or multi-give-and-take variables do non neglect syntactically because the value is expanded later the IF command is parsed:

Some other departure in Windows 2000 or college is that an empty variable (undefined) is not substituted. Equally described in previous examples, previous batch interpreter behaviour would have resulted in an empty cord. Example:

                        C:\>            ready            MyVar            =            C:\>            echo            %MyVar%            %MyVar%            C:\>            if            "            %MyVar%            "            ==            ""            (            repeat            MyVar is not divers)            else            (            echo            MyVar is            %MyVar%            )            MyVar is %MyVar%          

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

Quotation marks and spaces in passed strings [edit]

Dissimilar Unix/POSIX processes, which receive their control-line arguments already split up past the shell into an assortment 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 tin can implement its own parser to split up the entire command line into arguments. Many applications and command-line tools have evolved their own syntax for doing that, and so at that place is no single convention for quoting or escaping metacharacters on Windows command lines.

• For some commands, spaces are treated as delimiters that dissever arguments, unless those spaces are enclosed by quotation marks. Various conventions be of how quotation marks tin 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 marker (") produce n backslashes followed by a begin/end quote, whereas (iin)+1 backslashes followed by a quotation mark once more produce n backslashes followed by a quotation marker literal. The same convention is role of the .NET Framework specification.^[7]
    • An undocumented attribute is that "" occurring in the eye of a quoted cord produces a single quotation marker.^[7] (A CRT modify in 2008 [msvcr90] modified this undocumented handling of quotes.^[8]) This is helpful for inserting a quotation mark in an statement 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 marker (") is not included equally part of the string. Notwithstanding, an escaped quotation mark (""") can be role of the string.^{[ commendation needed ]}
  • Yet another mutual convention comes from the employ of Cygwin-derived ported programs. It does not differentiate between backslashes occurring before or not before quotes. Come across glob (programming) § Windows and DOS for information on these alternative command-line parsers.^[ix]
  • Some important Windows commands, like cmd.exe and wscript.exe, utilise their own rules.^[8]
• For other commands, spaces are not treated as delimiters and therefore practise not need quotation marks. If quotes are included they become part of the string. This applies to some built-in commands like repeat.

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 machinery is required:

                        C:\>            ready            foo            =            "this cord is enclosed in quotation marks"            C:\>            echo            "examination 1                        %foo%            "            "test i "this cord is enclosed in quotation marks""            C:\>eventcreate /T Alert /ID 1 /L System /So            "Source"            /D            "Example:                        %foo%            "            ERROR: Invalid Argument/Selection - 'cord'.            Type "EVENTCREATE /?" for usage.          

On Windows 2000 and afterward, the solution is to supercede each occurrence of a quote character within a value past a series of three quote characters:

                        C:\>            gear up            foo            =            "this string is enclosed in quotes"            C:\>            set            foo            =            %foo:"="""%            C:\>            echo            "examination 1                        %foo%            "            "exam 1 """this cord is enclosed in quotes""""            C:\>eventcreate /T Alarm /ID one /L System /SO            "Source"            /D            "Case:                        %foo%            "            SUCCESS: A 'Warning' type event is created in the 'Source' log/source.          

Escaped characters in strings [edit]

Some characters, such equally pipage (|) characters, have special pregnant to the command line. They cannot be printed as text using the ECHO command unless escaped using the caret ^ symbol:

                        C:\>            Echo            foo            |            bar            'bar' is not recognized as an internal or external command,            operable program or batch file.            C:\>            Echo            foo            ^|            bar            foo | bar          

Nonetheless, escaping does not work as expected when inserting the escaped character into an environment variable. The variable ends up containing a alive pipe command when merely echoed. It is necessary to escape both the caret itself and the escaped character for the grapheme brandish as text in the variable:

                        C:\>            set            foo            =bar            |            baz            'baz' is not recognized equally an internal or external command,            operable plan or batch file.            C:\>            set            foo            =bar            ^|            baz            C:\>            echo            %foo%            'baz' is not recognized as an internal or external command,            operable program or batch file.            C:\>            gear up            foo            =bar            ^^^|            baz            C:\>            echo            %foo%            bar | baz          

The delayed !VARIABLE! expansion available with CMD /5:ON or with SETLOCAL ENABLEDELAYEDEXPANSION in Windows 2000 and after may exist used to prove special characters stored in surround variables considering the variable value is expanded after the control was parsed:

                        C:\>cmd /Five:ON            Microsoft Windows [Version 6.1.7601]            Copyright (c) 2009 Microsoft Corporation. All rights reserved.            C:\>            set            foo            =bar            ^|            baz            C:\>            repeat            !foo!            bar | baz          

Sleep or scripted delay [edit]

Until the TIMEOUT control was introduced with Windows Vista, there was no easy mode to implement a timed intermission, equally the Intermission command halts script activeness indefinitely until any key is pressed.

Many workarounds were possible,^[10] merely by and large merely worked in some environments: The Choice command was non available in older DOS versions, PING was only available if TCP/IP was installed, and so on. No solution was bachelor from Microsoft, but a number of pocket-size utility programs, could be installed from other sources. A commercial case would exist the 1988 Norton Utilities Batch Enhancer (BE) command, where Be Filibuster 18 would wait for one 2d, or the free 94-byte Await.COM^[xi] where WAIT 5 would expect for 5 seconds, then return control to the script. About such programs are 16-bit .COM files, so are incompatible with 64-scrap Windows.

Text output with stripped CR/LF [edit]

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

• batchtest.bat

                                          C:\>batchtest.bat                    foo                    bar                  

It does not thing if the ii echo commands share the same command line; the CR/LF codes are inserted to break the output onto separate lines:

                        C:\>            @            echo            Message i&@            repeat            Bulletin 2            Message 1            Message 2          

A play a joke on discovered with Windows 2000 and later is to use the special prompt for input to output text without CR/LF abaft the text. In this example, the CR/LF does non follow Bulletin 1, just does follow Line ii and Line 3:

• batchtest2.bat

                                          @                    echo                    off                    set                    /p                    =                    "Message one"                    <nul                    echo                    Message 2                    repeat                    Message three                  

                                          C:\>batchtest2.bat                    Message 1Message 2                    Message 3                  

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

                        C:\>            set up            /p            =            "Message i"            <nul            >information.txt            C:\>            set            /p            =            "Message ii"            <nul            >>data.txt            C:\>            gear up            /p            =            "Message three"            <nul            >>data.txt            C:\>            blazon            information.txt            Bulletin 1Message 2Message three          

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

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

It is not possible to have a command prompt that uses a UNC path as the current working directory; east.g. \\server\share\directory\

The command prompt requires the employ of drive letters to assign a working directory, which makes running complex batch files stored on a server UNC share more hard. While a batch file can exist run from a UNC file path, the working directory default is C:\Windows\System32\.

In Windows 2000 and subsequently, a workaround is to use the PUSHD and POPD command with command extensions.^{[nb two]}

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

So to run a batch file on a UNC share, assign a temporary drive letter to the UNC share, and use the UNC share every bit the working directory of the batch file, a Windows shortcut tin can exist synthetic that looks like this:

• Target: %COMSPEC% /E:ON /C "PUSHD """\\SERVER\SHARE\DIR1\DIR2\""" & BATCHFILE.BAT & POPD"

The working directory attribute of this shortcut is ignored.

This besides solves a trouble related to User Account Control (UAC) on Windows Vista and newer. When an administrator is logged on and UAC is enabled, and they try to run a batch file as administrator from a network drive letter, using the right-click file context menu, the operation will unexpectedly fail. This is because the elevated UAC privileged business relationship context does not have network bulldoze letter assignments, and it is not possible to assign drive messages for the elevated context via the Explorer beat or logon scripts. Still, by creating a shortcut to the batch file using the above PUSHD / POPD construct, and using the shortcut to run the batch file as administrator, the temporary drive letter of the alphabet will be created and removed in the elevated business relationship context, and the batch file volition function correctly.

The following syntax does correctly expand to the path of the current batch script.

%~dp0        

UNC default paths are turned off by default as they used to crash older programs.^[12]

The Dword registry value DisableUNCCheck at HKEY_CURRENT_USER\Software\Microsoft\Command Processor ^[12] allows the default directory to be UNC. CD command will refuse to change but placing a UNC path in Default Directory in a shortcut to Cmd or by using the Start command. starting time "" /d \\127.0.0.1\C$ "cmd /k" (C$ share is for administrators).

Character set [edit]

Batch files use an OEM character set up, as defined by the calculator, east.g. Lawmaking page 437. The not-ASCII parts of these are incompatible with the Unicode or Windows character sets otherwise used in Windows so care needs to be taken.^[thirteen] Non-English language file names piece of work only if entered through a DOS character set compatible editor. File names with characters outside this set do not work in batch files.

To get output in Unicode into file pipes from an internal command such as dir, one tin utilize the cmd /U control. For case, cmd /U /C dir > files.txt creates a file containing a directory listing with right Windows characters, in the UTF-16LE encoding.

Batch viruses and malware [edit]

As with any other programming language, batch files can exist used maliciously. Simple trojans and fork bombs are hands created, and batch files tin exercise a course of DNS poisoning by modifying the hosts file. Batch viruses are possible, and tin can also spread themselves via USB wink drives by using Windows' Autorun adequacy.^[14]

The following command in a batch file volition delete all the data in the current directory (binder) - without offset asking for confirmation:

These iii commands are a uncomplicated fork flop that will continually replicate itself to deplete available system resources, slowing downwards or crashing the organization:

                        :            Superlative            kickoff            ""            %0            goto            Tiptop          

Other Windows scripting languages [edit]

The cmd.exe command processor that interprets .cmd files is supported in all 32- and 64-chip versions of Windows upward to at least Windows 10^[update]. COMMAND.EXE, which interprets .BAT files, was supported in all 16- and 32-bit versions up to at least Windows x.^{[nb 3]}

In that location are other, later and more than powerful, scripting languages available for Windows. However, these require the scripting linguistic communication interpreter to exist installed before they can be used:

• 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 elementary '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 tin run them in windowed fashion (with the wscript.exe host) or in panel-based mode (with the cscript.exe host). They have been a office 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 as well via saved scripts, and has a strong resemblance to Unix shells.^[15]
• Unix-manner shell scripting languages can be used if a Unix compatibility tool, such every bit Cygwin, is installed.
• Cross-platform scripting tools including Perl, Python, Ruby, Rexx, Node.js and PHP are bachelor for Windows.

Script files run if the filename without extension is entered. There are rules of precedence governing interpretation of, say, DoThis if DoThis.com, DoThis.exe, DoThis.bat, DoThis.cmd, etc. exist; by default DoThis.com has highest priority. This default social club may exist modified in newer operating systems by the user-settable PATHEXT environment variable.

See besides [edit]

• Listing of DOS commands

Notes [edit]

1. ^ To verify that COMMAND.COM remains available (in the \WINDOWS\SYSTEM32 directory), blazon Command.COM at the 32-bit Windows 7 command prompt.
2. ^ "If Control Extensions are enabled the PUSHD command accepts network paths in improver to the normal bulldoze letter and path. If a network path is specified, PUSHD creates a temporary drive letter that points to that specified network resource and so change the current drive and directory, using the newly defined drive letter. Temporary drive letters are allocated from Z: on down, using the first unused drive letter establish." --The help for PUSHD in Windows seven
3. ^ Availability of CMD.EXE and Command.COM can be confirmed by invoking them in whatever version of Windows (COMMAND.COM not in 64-bit versions; probably simply available in Windows 8 32-bit versions if installed with option to support 16-chip programs).

References [edit]

1. ^ "Using batch files: Scripting; Management Services". Technet.microsoft.com. 2005-01-21. Retrieved 2012-xi-xxx .
2. ^ Henry-Stocker, Sandra (2007-07-18). "Use your Unix scripting skills to write a batch file". itworld.com. Information technology World. Retrieved 2018-06-13 .
3. ^ "Departure betwixt bat and cmd | WWoIT - Wayne's Globe of Information technology". waynes-world-it.blogspot.fr. 2012-11-15. Retrieved 2012-11-30 .
4. ^ "btm file extension :: all near the .btm file type". Cryer.co.u.k.. Retrieved 2012-11-30 .
5. ^ Caldera DR-DOS 7.02 User Guide, Caldera, Inc., 1998 [1993, 1997], archived from the original on 2016-11-05, retrieved 2013-08-x
6. ^ Brothers, Hardin; Rawson, Tom; Conn, Rex C.; Paul, Matthias R.; Dye, Charles E.; Georgiev, Luchezar I. (2002-02-27). 4DOS eight.00 online help.
7. ^ ^{a b} ".Net Core Runtime: Organization.Diagnostics.Process.Unix". GitHub . Retrieved 2020-02-11 . Two sequent double quotes inside an inQuotes region should event in a literal double quote (the parser is left in the inQuotes region). This behavior is non part of the spec of code:ParseArgumentsIntoList, simply is uniform with CRT and .NET Framework.
8. ^ ^{a b} Deley, David. "How Command Line Parameters Are Parsed".
9. ^ "Child process documentation, section Windows Control Line, NodeJS PR #29576". GitHub . Retrieved 2020-02-11 .
10. ^ "How to do a delay", ericphelps.com
11. ^ Utilities for DOS, linking to Expect.ZIP (archive of WAIT.COM) and other programs
12. ^ ^{a b} https://support.microsoft.com/en-u.s./kb/156276 ^{[ dead link ]}
13. ^ Chen, Raymond. "Continue your middle on the code page". Microsoft.
14. ^ http://www.explorehacking.com/2011/01/batch-files-fine art-of-creating-viruses.html
15. ^ "Windows PowerShell - Unix comes to Windows". Geekswithblogs.net. Retrieved 2012-eleven-xxx .

External links [edit]

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

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Source: https://en.wikipedia.org/wiki/Batch_file

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