Windows batch files bat vs cmd

Question

As I understand it   bat is the old 16-bit naming convention  and  cmd is for 32-bit Windows  i e   starting with NT  But I continue to see  bat files everywhere  and they seem to work exactly the same using either suffix  Assuming that my code will never need to run on anything older than NT  does it really matter which way I name my batch files  or is there some gotcha awaiting me by using the wrong suffix

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Still  on Windows 7  BAT files have also this difference   If you ever create files TEST BAT and TEST CMD in the same directory  and you run TEST in that directory  it ll run the BAT file   C   gt echo  PATHEXT   COM  EXE  BAT  CMD  VBS  VBE  JS  JSE  WSF  WSH  MSC  C  Temp gt echo echo bat  gt  test bat  C  Temp gt echo echo cmd  gt  test cmd  C  Temp gt test  C  Temp gt echo bat bat  C  Temp gt

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No - it doesn t matter in the slightest   On NT the  bat and  cmd extension both cause the cmd exe processor to process the file in exactly the same way   Additional interesting information about command com vs  cmd exe on WinNT-class systems from MS TechNet  http   technet microsoft com en-us library cc723564 aspx       This behavior reveals a quite subtle   feature of Windows NT that is very   important  The 16-bit MS-DOS shell    COMMAND COM  that ships with Windows   NT is specially designed for Windows   NT  When a command is entered for   execution by this shell  it does not   actually execute it  Instead  it   packages the command text and sends it   to a 32-bit CMD EXE command shell for   execution  Because all commands are   actually executed by CMD EXE  the   Windows NT command shell   the 16-bit   shell inherits all the features and   facilities of the full Windows NT   shell

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Slightly off topic  but have you considered Windows Scripting Host  You might find it nicer

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I believe if you change the value of the ComSpec environment variable to  SystemRoot system32 cmd exe CMD  then it doesn t matter if the file extension is  BAT or  CMD  I m not sure  but this may even be the default for WinXP and above

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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

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everything working in a batch should work in a cmd  cmd provides some extensions for controlling the environment  also  cmd is executed by in new cmd interpreter and thus should be faster  not noticeable on short files  and stabler as bat runs under the NTVDM emulated 16bit environment

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These answers are a bit too long and focused on interactive use   The important differences for scripting are     cmd prevents inadvertent execution on non-NT systems   cmd enables built-in commands to change Errorlevel to 0 on success    Not that exciting  eh   There used to be a number of additional features enabled in  cmd files  called Command Extensions   However  they are now enabled by default for both  bat and  cmd files under Windows 2000 and later   Bottom line  in 2012 and beyond  I recommend using  cmd exclusively

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Since the original post was regarding the consequences of using the  bat or  cmd suffix  not necessarily the commands inside the file     One other difference between  bat and  cmd is that if two files exist with the same file name and both those extensions  then    entering filename or filename bat at the command line will run the  bat file to run the  cmd file  you have to enter filename cmd

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cmd and  bat file execution is different because in a  cmd errorlevel variable it can change on a command that is affected by command extensions  That s about it really

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The extension makes no difference   There are slight differences between COMMAND COM handling the file vs CMD EXE

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RE  Apparently when command com is invoked is a bit of a complex mystery   Several months ago  during the course of a project  we had to figure out why some programs that we wanted to run under CMD EXE were  in fact  running under COMMAND COM  The  program  in question was a very old  BAT file  that still runs daily   We discovered that the reason the batch file ran under COMMAND COM is that it was being started from a  PIF file  also ancient   Since the special memory configuration settings available only through a PIF have become irrelevant  we replaced it with a conventional desktop shortcut   The same batch file  launched from the shortcut  runs in CMD EXE  When you think about it  this makes sense  The reason that it took us so long to figure it out was partially due to the fact that we had forgotten that its item in the startup group was a PIF  because it had been in production since 1998

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a difference    cmd files are loaded into memory before being executed    bat files execute a line  read the next line  execute that line      you can come across this when you execute a script file and then edit it before it s done executing   bat files will be messed up by this  but cmd files won t

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Here is a compilation of verified information from the various answers and cited references in this thread    command com is the 16-bit command processor introduced in MS-DOS and was also used in the Win9x series of operating systems  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  The ComSpec env variable defines which program is launched by  bat and  cmd scripts   Starting with WinNT this defaults to cmd exe   cmd exe is backward compatible with command com  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     amp     gt   lt     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

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