Environment variables from the command line. Basics of BAT files

To display the help text not on the screen, but in a file, you can use redirecting output ... When using the command line, the standard input is the keyboard and the output is the display, but these devices can be reassigned using redirection characters

< - redirecting input

> - redirecting output (or\u003e\u003e - redirecting to an existing file when the output is appended to the end of the file.)

To output the data stream of the commandHELP to the file help.txt the command line will be as follows:

HELP\u003e help.txt

To display help for a GOTO command in a goto.txt file:

The value of some variables is not displayed by the SET command. These are variables whose values \u200b\u200bare dynamically changed:

% CD% - Takes the value of the current directory line.

% DATE% - Takes the value of the current date.

% TIME% - Takes the value of the current time.

% RANDOM% - Accepts a random decimal value in the range 1 -32767.

% ERRORLEVEL% - Takes the current value of the ERRORLEVEL task completion code

% CMDEXTVERSION% - Takes the command shell version CMD.EXE for extended command processing.

% CMDCMDLINE% - Takes the value of the line that invoked the command processor.

You can use the command line to view the value of a variable:

Input parameters for the batch file.

It is possible to pass command line parameters to a batch file and use their values \u200b\u200bin statements of the batch file itself.

In the very command file the first parameter will be available as a variable %1 , the second - %2 etc. The name of the batch file itself is available as a variable %0 ... For example, let's create a command file whose task will be to display the values \u200b\u200bof the entered parameters on the screen. Usually the command is used to display text

ECHO< текст >

However, if the text is replaced by% 1, the first parameter will be displayed, by% 2 - the second, etc.

Create a parm.bat file with the following content:

echo First parameter \u003d% 1

echo Second parameter \u003d% 2

echo Third parameter \u003d% 3

and run it with the following command:

parm.bat FIRST second “two words”

after completing it, you will understand how it works and that parameters with spaces must be enclosed in double quotes. To prevent lines processed by the command processor from being displayed on the screen, you can use the commandECHO OFFby placing it on the first line of the batch file. To make a line of a command file be ignored by the shell, place at the beginning of it REM< пробел > ... In this way, you can place comments, often useful in large batch files:

rem ECHO OFF turns off the mode of displaying the contents of lines of a command file on the screen

REM will only display the result of their execution.

echo First parameter \u003d% 1

echo Second parameter \u003d% 2

echo Third parameter \u003d% 3

Try to replace ECHO OFF with @ECHO OFF - the result speaks for itself. The line that turns off the output mode is no longer displayed on the screen.

Transitions and labels.

To find a file on disk, use the commandIF EXIST:

IF EXIST filename command

The easiest command is to useSUBSTmapping a drive name to a directory.

SUBST X: C: - creates a virtual disk X: with the contents of the root directory of the C:

Create a batch file setXY.bat with the following lines:

After executing such a file, you will have disks X: and Y: But if you execute such a file again, the SUBST command will display an error message - after all, disks X: and Y: already exist.

It is advisable to bypass the execution of SUBST if the virtual disks X: and Y: have already been created (or delete them using SUBST with the -d option before connecting). We modify the batch file usingGOTO - transfer of control to the line of the batch file by label.

GOTO label

The label must be on a separate line and start with a colon. Let's make changes in our batch file so that no error messages appear:

REM if X does not exist: - then go to the label SETX

IF NOT EXIST X: GOTO SETX

REM if X exists: - go to check for Y:

IF EXIST G: flashd1.let SUBST X: G:

IF EXIST F: flashd1.let SUBST X: F:

REM if Y: exists - terminate the batch file.

IF EXIST Y: GOTO EXIT

IF EXIST G: flashd2.let SUBST Y: G:

IF EXIST F: flashd2.let SUBST Y: F:

REM exit from batch file

The SUBST error message disappeared. Symptoms of errors during command execution can be tracked in the command file itself by analyzing the variableERRORLEVEL, the value of which is formed during the execution of most programs. ERRORLEVEL is 0 if the program exited without error and 1 if an error occurred. There may be other values \u200b\u200bas well, if they are provided in the executable program.

You can also use a batch file as a command in the line of a batch file. Moreover, to transfer with a return back to the point of execution of the calling command file, use the commandCALL ... Let's create a batch file test.bat with the following content:

ECHO Call 1.bat

ECHO Return.

And 1.bat file containing the commandPAUSE,pauses the execution of the batch file until any key is pressed.

When test.bat is executed, a message will be displayed

Calling 1.bat

and control will get 1.bat with the pause command. After starting a key on the keyboard, the command line "ECHO Return." and the screen will display

If CALL is removed in test.bat, then return from file 1.bat will not be performed. By the way, using the transfer of control to a batch file, you can organize its looping. Try adding the following line to the end of the test.bat file:

You can exit the batch file loop by pressing CTRL-Break. It is possible to use the CALL command to call a procedure within a batch file. In this case, not the name is used as an argument external fileand the label is:
....
call: proc1
....
: proc1
....
exit
....

File creation.

Windows does not have a dedicated command to create a file, but it can be easily dispensed with in several ways:

Copy from console to file

COPY CON myfile.txt

When this command is executed, the data from the keyboard (device CON) will be written to the file myfile.txt. Pressing F6 or CTRL-Z will end the output.

Redirecting output

ECHO 1\u003e myfile.txt

Executing this command will create a file myfile.txt containing the character “1”

Combination of input and output redirection:

COPY CON\u003e myfile.txt< xyz

When executing this command, as in the first case, copying from the console to a file is used, but instead of data from the keyboard, input from a non-existent device xyz is used. The system will display a message stating that such a device does not exist, but the empty file myfile.txt will be successfully created.
A very simple option is to copy from a dummy device with a name nul to the file.
copy nul myfile.txt

If you often have to create empty files, you can prepare your own batch file (for example, newfile.bat or, even better, nf.bat), and pass the name of the file to be created as a parameter at startup.

File contents:

Place this batch file in your system directory (C: windowssystem32 or whatever is in the PATH search paths).

Command line:

newfile.bat myfile.txt

Or

nf.bat myfile.txt

Or
nf myfile.txt

Here's the command nf for creating empty file at command line.

Assigning the same drive letter to a removable disk.

@echo off
ECHO PROCESSING FILE -% 0
ECHO Date / time of creation / modification of the batch file -% ~ t0
ECHO Batch file path - "% ~ f0"
ECHO Batch File Disk -% ~ d0
ECHO Batch file directory - "% ~ p0"
ECHO Command file name -% ~ n0
ECHO Batch file extension -% ~ x0
ECHO Short name and extension -% ~ s0
ECHO Batch File Attributes -% ~ a0
ECHO Batch file size -% ~ z0

Generation of archives by date and time.

Let's solve the following problem - you need to create an archive of files located in the C: Program FilesFAR directory. The name of the archive file must consist of the current time (hours.minutes.seconds - HH.MM.SS.rar), and it must be placed in a new directory, the name of which must consist of the current date (day.month.year - DD.MM. YYYY). For archiving, we will use the RAR archiver. Startup format for creating an archive:

RAR a -r< путь и имя архива > < Путь и имя архивируемых данных >

a- command to create an archive.
-r - a key that determines the archiving of subdirectories (since there are subdirectories in the source folder).

Thus, to solve the problem, you need to correctly create the names and paths for RAR. For what we will use the following factors:

Sometimes it is required to form date and time variable at cmd / bat scripts windowsthe way we need, and not the way the operating system gives us.

For example, to add this data to the log file, to fix the time or date of the event, create a file with a name in which the date or time data should appear (day, month, year, hour, minutes, skunda, milliseconds.) Yes, you never know, what are our tasks ... We connect our imagination :)

In the next example, we see the breakdown of variables according to the templates we need.

h- hour 2 characters (that is, the hour will be issued in as follows - 01, 02, ..., 09, ... , 12, ... 24)

m - minutes 2 characters

s - seconds 2 characters

ms - milliseconds 2 characters, for some reason from 0 to 99

dd - day 2 characters

mm - month 2 characters

yyyy - year 4 characters

Example of using variables % DATE% and % TIME% in scripts cmd / bat Windows:

@echo off
set h \u003d% TIME: ~ 0.2%
set m \u003d% TIME: ~ 3.2%
set s \u003d% TIME: ~ 6.2%
set ms \u003d% TIME: ~ 9.2%
set curtime \u003d% h%:% m%:% s%:% ms%
set dd \u003d% DATE: ~ 0.2%
set mm \u003d% DATE: ~ 3.2%
set yyyy \u003d% DATE: ~ 6.4%
set curdate \u003d% dd% -% mm% -% yyyy%
set curdatetime \u003d% curdate%% curtime%

echo The current time is% curdatetime%

In some versions Windows format issuing the date and time is different, so this script can work exactly as we need.

In theory, in a similar way you can take parts of any variables, the point is that the format is like this:

The first digit after: ~ is the number of the character from which we start taking the value, the second digit is how many characters to capture.

Thus, it turns out that we can take for our needs any part, any variable of the Windows environment available to us.

I know the following variables, the values \u200b\u200bof which we can get:

Inside the command files, you can work with the so-called environment variables (or environment variables), each of which is stored in random access memory, has a unique name, and its value is a string. Standard environment variables are automatically initialized during the boot process of the operating system. Such variables are, for example, WINDIR, which specifies the location of the Windows directory, TEMP, which specifies the path to the directory for storing temporary windows files or PATH, which stores the system path (search path), that is, a list of directories in which the system should look for executable files or files sharing (like dynamic libraries). In addition, you can declare your own environment variables in batch files using the SET command.

Getting the value of a variable

To get the value of a specific environment variable, enclose the variable name in% characters. For instance:

@ECHO OFF CLS REM Create variable MyVar SET MyVar \u003d Hello REM Change variable SET MyVar \u003d% MyVar%! ECHO The value of the variable MyVar:% MyVar% REM Deleting the variable MyVar SET MyVar \u003d ECHO The value of the variable WinDir:% WinDir%

When you run such a command file, the line will be displayed on the screen

The value of the variable MyVar: Hello! The value of the WinDir variable: C: \\ WINDOWS

Converting Variables as Strings

You can do some manipulation with environment variables in batch files. First, concatenation (gluing) operation can be performed on them. To do this, you just need to write the values \u200b\u200bof the variables to be connected in the SET command. For instance,

SET A \u003d One SET B \u003d Two SET C \u003d% A %% B%

After these commands are executed in the file, the value of the C variable will be the string "Div2" You should not use the + sign for concatenation, as it will simply be taken as a symbol. For example, after starting the file with the following content

SET A \u003d One SET B \u003d Two SET C \u003d A + B ECHO Variable C \u003d% C% SET D \u003d% A% +% B% ECHO Variable D \u003d% D%

two lines will be displayed on the screen:

Variable C \u003d A + B Variable D \u003d One + Two

Secondly, substrings can be extracted from an environment variable using the construction % variable_name: ~ n1, n2%, where the number n1 defines the offset (the number of characters to skip) from the beginning (if n1 is positive) or from the end (if n1 is negative) of the corresponding environment variable, and the number n2 is the number of characters to be allocated (if n2 is positive) or the number of last characters in the variable that will not be included in the selected substring (if n2 is negative). If only one negative -n option is specified, the last n characters will be extracted. For example, if the variable% DATE% stores the string "09/21/2007" (symbolic representation of the current date under certain regional settings), then after executing the following commands

SET dd1 \u003d% DATE: ~ 0.2% SET dd2 \u003d% DATE: ~ 0, -8% SET mm \u003d% DATE: ~ -7.2% SET yyyy \u003d% DATE: ~ -4%

new variables will have the following values: % dd1% \u003d 21,% dd2% \u003d 21,% mm% \u003d 09,% yyyy% \u003d 2007.

Thirdly, you can perform the procedure for replacing substrings using the construction % variable_name: s1 \u003d s2% (This will return a string with each occurrence of the substring s1 in the corresponding environment variable replaced with s2). For example, after executing the commands

SET a \u003d 123456 SET b \u003d% a: 23 \u003d 99%

variable b will store the string "199456". If the s2 parameter is not specified, the s1 substring will be removed from the output string, i.e. after executing the command

SET a \u003d 123456 SET b \u003d% a: 23 \u003d%

variable b will store the string "1456".

Operations on Variables as Numbers

When extended command processing is enabled (this mode is used by default in Windows XP), it is possible to treat the values \u200b\u200bof environment variables as numbers and perform arithmetic calculations with them. To do this, use the SET command with the / A switch. Here is an example of a batch file add.bat that adds two numbers specified as command line parameters and displays the resulting amount on the screen:

@ECHO OFF REM Variable M will store the sum of SET / A M \u003d% 1 +% 2 ECHO Sum of% 1 and% 2 equals% M% REM Delete variable M SET M \u003d

Changing variables locally

Any changes made to the environment variables in a command file using the SET command are saved after the file is finished, but they are effective only within the current command window. It is also possible to localize changes to environment variables inside a batch file, that is, to automatically restore the values \u200b\u200bof all variables in the form in which they were before starting this file. There are two commands used for this: SETLOCAL and ENDLOCAL. SETLOCAL command defines the beginning of the region local installations environment variables. In other words, environment changes made after SETLOCAL is run will be local to the current batch file. Each SETLOCAL command must have a corresponding ENDLOCAL command to restore the previous values \u200b\u200bof environment variables. Environment changes made after the ENDLOCAL command were executed are no longer local to the current batch file; their previous values \u200b\u200bwill not be restored when the execution of this file is complete.

Wednesday shell cmd.exe is defined by variables that control the behavior of the shell and operating system.

It is possible to define the behavior of the shell environment or the entire operating system environment using two types of environment variables: system and local.

System environment variables determine the behavior of the global operating system environment, and local environment variables determine the behavior of the environment in a given instance of cmd.exe.

System environment variables are conveniently set in the operating system and are available to all Windows processes, and users with administrator privileges can modify these variables. These variables are most commonly used in logon scripts.

Local environment variables are available when the user for whom they were created is logged in. Local variables from the registry hive HKEY_CURRENT_USER are only suitable for the current user, but define the behavior of the global operating system environment.

List of variable types in descending order of precedence.

1. Built-in system variables
2. Registry hive system variables HKEY_LOCAL_MACHINE
3. Registry hive local variables HKEY_CURRENT_USER
4. All environment variables and paths are specified in the file Autoexec.bat.
5. All environment variables and paths are specified in the login script (if present).
6. Variables used interactively in a script or batch file

In the command shell, each instance of cmd.exe inherits the environment of its parent application, and accordingly, you can change the variables in the new environment, cmd.exe, without affecting the environment of the parent application.

Here is a list of system and local environment variables for Windows XP.

Sets, removes, and views environment variables. Called without parameters, the command set lists the set environment variables and their values.

Syntax

set [[/ a [expression]] [/ p [variable = ]] line]

Parameters

Notes

• Using the command set in the recovery console

  Command set with different parameters is available in the Recovery Console.

• Using special characters

  Symbols<, >, |, &, ^ are special shell characters, you must either precede them with a control character (^) or enclose them in quotation marks when using characters in the parameter line (eg, " content_string & symbol" ). When you quote a string containing special symbols, quotes are considered part of the value of the environment variable.

• Using environment variables

  Environment variables are used to control how some batch files and programs work and to control windows operation XP and MS-DOS Subsystems. Command set often used in Autoexec.nt file to set environment variables.

• Displaying current environment settings

  When the team set called without parameters, the current settings will be displayed. Typically these settings include the COMSPEC and PATH variables used to find programs on disk. Two other environment variables used by Windows are PROMPT and DIRCMD.

• Using parameters

  When specifying values \u200b\u200bfor a variable and a string, the value of the variable is added to the environment, and the string is mapped to this variable. If the variable already exists, the new value overwrites the old value.

  If the team set only the variable name and the equal sign (no value) are specified, any value will no longer be mapped to an environment variable, which is equivalent to removing the environment variable.

• Using / a

  The following table lists the operators that support the parameter / a, in descending order.

  Using logical operators (&& ||) or the modulus operator (%), enclose the string expression in quotation marks. Any non-numeric strings in the expression are considered environment variable names whose values \u200b\u200bare converted to numbers before being processed. If an environment variable name is specified that is not defined in the current environment, it is assigned a value of zero, allowing arithmetic operations on the values \u200b\u200bof the environment variable without using% to get the value.

  When executing the command set / a from the command line outside of the command script, the final value of the expression is printed.

  Numerical values \u200b\u200bare decimal numbers, except for numbers prefixed with 0x for hexadecimal numbers and 0 for octal numbers. Thus, 0x12 is the same as 18 and 022. Octal representation requires precision. For example, 08 and 09 are invalid because 8 and 9 are not octal digits.

• Using / p

  Used when you do not need to include the command line.

• Support for delayed environment variable expansion

  Added support for delayed environment variable expansion. This support is disabled by default, you can enable or disable it using the command cmd / v.

• Working with team extensions

  With command extensions enabled (set by default) and command execution set without values, all current environment variables are displayed. If the command is executed set with a value, the variables corresponding to that value are displayed.

• Using the command set in batch files

  When creating batch files, use the command set to create variables and use them as numeric variables from %0 before %9 ... You can also use variables from %0 before %9 as input for the command set.

• Accessing command variables set from batch programs

  When referring to a variable from a batch program, the variable name must be enclosed in percent signs (%). For example, if a BAUD variable is created in a batch program, a replacement parameter can be associated with it by using the name % baud% at the command line.

Examples of

To set an environment variable named TEST ^ 1, enter the command:

set testVar \u003d test ^^ 1

To set an environment variable named TEST & 1, enter the command:

set testVar \u003d test ^ & 1

The value of the command variable set defines everything that follows the equal sign (\u003d). When typing:

set testVar \u003d "test ^ 1"

The result will be as follows:

testVar \u003d "test ^ 1"

You can use the following command to set the INCLUDE environment variable so that the line C: \\ Inc (the Inc directory on drive C) is associated with it:

set include \u003d c: \\ inc

You can use the string C: \\ Inc in batch files by enclosing the INCLUDE name in percent signs (%). For example, in a batch file, you can use the following command to list the contents of the directory pointed to by the INCLUDE environment variable:

When executing the command, the line % include% will be replaced by the string C: \\ Inc.

You can also use the command set in a batch program that adds a new directory to your PATH environment variable. For instance:

@echo off
rem ADDPATH.BAT adds a new directory
rem to the path environment variable.
set path \u003d% 1;% path%
set

With command extensions enabled (set by default) and command execution set with a value, all environment variables matching the value are displayed. For example, when typing on the command line: set p, the result will be as follows:

Path \u003d C: \\ WINNT \\ system32; C: \\ WINNT; C: \\ WINNT \\ System32 \\ Wbem
PATHEXT \u003d .COM; .EXE; .BAT; .CMD; .VBS; .VBE; .JS; .JSE; .WSF; .WSH
PROCESSOR_ARCHITECTURE \u003d x86
PROCESSOR_IDENTIFIER \u003d x86 Family 6 Model 8 Stepping 1, GenuineIntel
PROCESSOR_LEVEL \u003d 6
PROCESSOR_REVISION \u003d 0801
ProgramFiles \u003d C: \\ Program Files
PROMPT \u003d $ P $ G

Some techniques and features of working with the Set command can be found in the Arithmetic Data Processing section.

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