Windows batch files: .bat vs .cmd?

Solution 1:

From this news group posting by Mark Zbikowski himself:

The differences between .CMD and .BAT as far as CMD.EXE is concerned are: With extensions enabled, PATH/APPEND/PROMPT/SET/ASSOC in .CMD files will set ERRORLEVEL regardless of error. .BAT sets ERRORLEVEL only on errors.

In other words, if ERRORLEVEL is set to non-0 and then you run one of those commands, the resulting ERRORLEVEL will be:

• left alone at its non-0 value in a .bat file
• reset to 0 in a .cmd file.

Solution 2:

Here is a compilation of verified information from the various answers and cited references in this thread:

0. command.com is the 16-bit command processor introduced in MS-DOS and was also used in the Win9x series of operating systems.
1. cmd.exe is the 32-bit command processor in Windows NT (64-bit Windows OSes also have a 64-bit version). cmd.exe was never part of Windows 9x. It originated in OS/2 version 1.0, and the OS/2 version of cmd began 16-bit (but was nonetheless a fully fledged protected mode program with commands like start). Windows NT inherited cmd from OS/2, but Windows NT's Win32 version started off 32-bit. Although OS/2 went 32-bit in 1992, its cmd remained a 16-bit OS/2 1.x program.
2. The ComSpec env variable defines which program is launched by .bat and .cmd scripts. (Starting with WinNT this defaults to cmd.exe.)
3. cmd.exe is backward compatible with command.com.
4. A script that is designed for cmd.exe can be named .cmd to prevent accidental execution on Windows 9x. This filename extension also dates back to OS/2 version 1.0 and 1987.

Here is a list of cmd.exe features that are not supported by command.com:

• Long filenames (exceeding the 8.3 format)
• Command history
• Tab completion
• Escape character: ^ (Use for: \ & | > < ^)
• Directory stack: PUSHD/POPD
• Integer arithmetic: SET /A i+=1
• Search/Replace/Substring: SET %varname:expression%
• Command substitution: FOR /F (existed before, has been enhanced)
• Functions: CALL :label

Order of Execution:

If both .bat and .cmd versions of a script (test.bat, test.cmd) are in the same folder and you run the script without the extension (test), by default the .bat version of the script will run, even on 64-bit Windows 7. The order of execution is controlled by the PATHEXT environment variable. See Order in which Command Prompt executes files for more details.

References:

• cmd.exe
• command.com

wikipedia: Comparison of command shells