| COMMAND |
|
| Starts a new instance of the MS-DOS command interpreter. |
|
| A command interpreter is a program that lets you type commands. Use the EXIT |
| command to stop the new command interpreter and return control to the old |
| one. |
|
| Syntax |
| COMMAND [[drive:]path] [device] [/E:nnnnn] [/Y [/C command|/K command]] |
|
| In your CONFIG.SYS file, use the following syntax: |
|
| SHELL=[[dos-drive:]dos-path]COMMAND.COM [[drive:]path][device] |
| [/E:nnnn] [/P [/MSG]] |
|
| Parameters |
|
| [drive:]path |
| Specifies the directory in which the command interpreter is to look for |
| the COMMAND.COM file when the transient part of the program needs to be |
| reloaded. This parameter must be included when loading COMMAND.COM for |
| the first time if the COMMAND.COM file is not located in the root |
| directory. This parameter is used to set the COMSPEC environment |
| variable. For more information, see Transient and Resident Memory in |
| COMMAND--Notes . |
|
| device |
| Specifies a different device for command input and output. For more |
| information about this parameter, see the CTTY command. |
|
| [dos-drive:]dos-path |
| Specifies the location of the COMMAND.COM file. |
|
| Switches |
|
| /C command |
| Specifies that the command interpreter is to perform the specified |
| command and then exit. This switch must be the last switch on the |
| command line. |
|
| /E:nnnnn |
| Specifies the environment size, where nnnnn is the size in bytes. The |
| value of nnnnn must be in the range 160 through 32768. MS-DOS rounds |
| this number up to a multiple of 16 bytes. The default value is 256. |
|
| /K command |
| Runs the specified command, program, or batch program and then displays |
| the MS-DOS command prompt. This switch must be the last switch on the |
| COMMAND command line. |
|
| This switch is particularly useful for specifying a startup batch file |
| for the MS-DOS Prompt in Windows (much like AUTOEXEC.BAT for MS-DOS). To |
| do this, open the DOSPRMPT.PIF file using the PIF Editor, and type the |
| /K switch in the Optional Parameters box. It is not recommended to use |
| the /K switch on the SHELL command line in your CONFIG.SYS file; doing |
| so can cause problems with applications and installation programs that |
| make changes to your AUTOEXEC.BAT file. |
|
| /P |
| Should be used only when COMMAND is used with the SHELL command in the |
| CONFIG.SYS file. The /P switch makes the new copy of the command |
| interpreter permanent. In this case, the EXIT command cannot be used to |
| stop the command interpreter. If you specify /P, MS-DOS runs your |
| AUTOEXEC.BAT file before displaying the command prompt. If there is no |
| AUTOEXEC.BAT file in the root directory of the startup drive, MS-DOS |
| carries out the DATE and TIME commands instead. If you do not have a |
| SHELL command in your CONFIG.SYS file, COMMAND.COM is automatically |
| loaded from the root directory with the /P switch. |
|
| /MSG |
| Specifies that all error messages should be stored in memory. Usually, |
| some messages are stored only on disk. This switch is useful only if you |
| are running MS-DOS from floppy disks. You must specify the /P switch |
| when you use the /MSG switch. For more information about using the /MSG |
| switch, see COMMAND--Notes . |
| /Y |
| Directs COMMAND.COM to step through the batch file specified by the /C |
| or /K switches. This switch is useful for debugging batch files. For |
| example, to step through the TEST.BAT batch file line by line, you would |
| type COMMAND /Y /C TEST. The /Y switch requires either the /C or the /K |
| switch. |
|
| Related Command |
|
| The SHELL command is the preferred method of using COMMAND to permanently |
| increase space for the environment table. |
|
|
| COMMAND--Notes |
|
| Limits on environment size |
|
| If nnnnn is less than 160 or greater than 32768, MS-DOS uses the default |
| value of 256 bytes and displays the following message: |
|
| Parameter value not in allowed range. |
|
| Changing your terminal device |
|
| You can specify a different device (such as AUX) for input and output by |
| using the device parameter. For more information about device, see the |
| CTTY command. |
|
| Running multiple command interpreters |
|
| When you start a new command interpreter, MS-DOS creates a new command |
| environment. This new environment is a copy of the parent environment. You |
| can change the new environment without affecting the old one. The default |
| size of the new environment is 256 bytes or the size of the current |
| environment rounded up to the next 16 bytes, whichever is larger. Use the /E |
| switch to override the default size. (Note that the current environment |
| refers to the memory actually being used, not to the environment size |
| specified with the previous /E switch.) |
|
| Transient and resident memory |
|
| MS-DOS loads the command interpreter in two parts: the resident part (which |
| is always in memory) and the transient part (at the top of conventional |
| memory). Some programs write over the transient part of COMMAND.COM when |
| they run. When this happens, the resident part must locate the COMMAND.COM |
| file on disk to reload the transient part. The COMSPEC environment variable |
| identifies where COMMAND.COM is located on the disk. If COMSPEC is set to a |
| floppy disk drive, MS-DOS might prompt you to insert a disk that contains |
| COMMAND.COM. |
|
| If MS-DOS is loaded in the HMA, a portion of resident COMMAND.COM is also |
| loaded into the HMA, making more conventional memory available for |
| programs. |
|
| Using the /MSG switch |
|
| Usually, MS-DOS leaves many error messages in the COMMAND.COM file on the |
| disk instead of using memory to store them. When MS-DOS needs to display one |
| of these messages, MS-DOS retrieves the message from the disk containing |
| COMMAND.COM. |
|
| If you are running MS-DOS from floppy disks instead of from a hard disk, |
| MS-DOS cannot retrieve such error messages unless you have the disk |
| containing COMMAND.COM in drive A. If this disk is not present, MS-DOS |
| displays one of the following short messages instead of the full message: |
|
| Parse error |
|
| Extended error |
|
| You can make sure MS-DOS displays complete error messages by using the /MSG |
| switch with COMMAND. This switch forces MS-DOS to keep these error messages |
| in memory so that they are always available when needed. |
|
| Use the /MSG switch with COMMAND if you have a floppy disk system, unless |
| you cannot afford to lose the memory used to store the error messages. |
|
| You must also specify the /P switch when you use the /MSG switch. |
|
| Internal commands |
|
| COMMAND is called a command processor because it reads any commands that you |
| type and processes them. |
|
| Some commands are recognized and carried out by COMMAND itself. These |
| commands are considered internal to COMMAND. Other MS-DOS commands are |
| separate programs located on your hard disk, which MS-DOS loads just like |
| your other programs. |
|
| The following MS-DOS commands are implemented by COMMAND: |
|
| BREAK ECHO REM |
| CALL EXIT RENAME (REN) |
| CHCP FOR RMDIR (RD) |
| CHDIR (CD) GOTO SET |
| CLS IF SHIFT |
| COPY LOADHIGH (LH) TIME |
| CTTY MKDIR (MD) TYPE |
| DATE PATH VER |
| DEL (ERASE) PAUSE VERIFY |
| DIR PROMPT VOL |
|
|
| COMMAND--Examples |
|
| The following command specifies that the MS-DOS command interpreter is to |
| start a new command interpreter from the current program, run a batch |
| program named MYBAT.BAT, and then return to the first command interpreter: |
|
| command /c mybat.bat |
|
| The following CONFIG.SYS command specifies that COMMAND.COM is located in |
| the DOS directory on drive C: |
|
| shell=c:\dos\command.com c:\dos\ /e:1024 |
|
| This command directs MS-DOS to set the COMSPEC environment variable to |
| C:\DOS\COMMAND.COM. This command also creates an environment of 1024 bytes |
| for this command interpreter. |
|
| The following command starts an instance of COMMAND.COM and runs the |
| MYBATCH.BAT file, stepping through the file command by command: |
|
| command /y /c mybatch.bat |
|
|
