Append - DOS/Command Prompt Reference

Options

If Append has been executed before, running Append without specifying any options will output the current appended directories.

* Once executed, Append operates as a resident program. After installing, you need to execute Append like an internal command (i.e. without specifying the extension ‘.exe’). If you try to run ‘append.exe’ with the extension, you will receive an error stating ‘Already installed’.

* Since Append is a resident program, you can use Loadhigh to load it into upper memory.

Search path with appended directories

When Append is installed (resident), it will influence certain file-related processes in MS-DOS system calls, incorporating appended directories into the file search path.

When appended directories are enabled, the search for the target file name occurs in the following order: ‘resolved path → each path in appended directories’ (after resolving the path based on the current directory). The first found file in this search sequence will be used.

• If the current directory is ‘C:\APPS’, appended directories are ‘D:\HOME;D:\BACKUP’, the target file name is ‘NOTE.TXT’, and ‘/PATH:ON’:
  → It will be searched in the following order: ‘C:\APPS\NOTE.TXT’,　‘D:\HOME\NOTE.TXT’, and ‘D:\BACKUP\NOTE.TXT’.
• If the current directory is ‘C:\APPS\TEST’, appended directories are ‘D:\HOME;D:\BACKUP’, the target file name is ‘..\RESULT.LOG’, and ‘/PATH:ON’:
  → It will be searched in the following order: ‘C:\APPS\RESULT.LOG’,　‘D:\HOME\RESULT.LOG’, and ‘D:\BACKUP\RESULT.LOG’.
• If the current directory is ‘C:\APPS’, appended directories are ‘D:\HOME;D:\BACKUP’, the target file name is ‘E:\ANOTHER.DAT’, and ‘/PATH:ON’:
  → It will be searched in the following order: ‘E:\ANOTHER.DAT’,　‘D:\HOME\ANOTHER.DAT’, and ‘D:\BACKUP\ANOTHER.DAT’.
• If the current directory is ‘C:\APPS’, appended directories are ‘D:\HOME;D:\BACKUP’, the target file name is ‘E:\ANOTHER.DAT’, and ‘/PATH:OFF’:
  → Since the path is included, appended directories will not be used, and only ‘E:\ANOTHER.DAT’ will be searched.

* ‘Resolving the path based on the current directory’ refers to the conversion that occurs when the target file name includes a relative or absolute path. In this process, the combination of the ‘current directory’ and the ‘relative or absolute path’ is used to create an absolute path. Please refer to the specific examples in the previous search scenarios.

Additionally, when "/X:ON" is set, appended directories are used in the search path during program execution. The order is as follows: ‘resolved path → each path in appended directories → each path in the PATH environment variable’. Please note that appended directories take precedence over PATH.

Appended directories and commands

Some commands always do not utilize appended directories. The confirmed commands include the following:

• Attrib
• Copy
• Del(Erase)
• If Exist syntax
• Ren(Rename)
• Xcopy

In addition to these, there is a possibility that appended directories may not be used in commands that directly manipulate files.

Also, when enumerating files in a directory using commands such as the Dir command, files in appended directories will not be added to the enumeration.

Appended directories and writing files

Appended directories are used during file reading or execution (/X:ON), but they are not utilized during file creation. Therefore, when opening a file from appended directories in an editor and attempting to save it directly, the file may be saved in the current directory (or strictly speaking, the resolved path). This behavior depends on the editor and, particularly, if the editor performs operations like ‘writing to a temporary file, deleting the original file, and then moving it’, the file may be saved in a location other than appended directories. When using appended directories for processes that involve writing, it is advisable to use it only with programs that do not create temporary files as part of their operations.

MS-DOS system calls (INT 21H interruption) using appended directories

In detail, when Append is embedded, the following MS-DOS system calls start utilizing appended directories:

• 0FH - open an existing file
• 23H - retrieve the file size
• 3DH - open an existing file with a handle

‘16H create a file (or truncate to size 0)’, among others, is exempt from this, leading to the behavior mentioned earlier where ‘appended directories are not utilized’ during file writing operations.

Additionally, when ‘/X:ON’ is set, the following MS-DOS system calls also start using appended directories:

• 11H - find the first file
• 4BH - execute a program
• 4EH - find the first file with retrieving additional information

Loading Append and /E option

Append becomes resident in the system during its initial execution, and subsequent calls to ‘Append’ utilize the resident Append program for processing. Since it is purely resident, the configuration settings are lost when the system is reset (rebooted).

When using the "/E" switch for resident mode, Append starts saving appended directories to the environment variable ‘APPEND’. However, since this is still just an environment variable, the configuration settings are lost when the system is reset. Nevertheless, using the environment variable allows you to retrieve the appended directories setting values, making them visible in listings with commands like Set and available for environment variable expansion using the ‘%’ character.

* If installed with the ‘/E’ option, you can also modify appended directories by overwriting the ‘APPEND’ environment variable using the Set command. Additionally, if the ‘APPEND’ environment variable is set before installing with the ‘/E’ option, the value becomes the appended directories when installed.