XXX is not recognized as an internal or external command, operable program or batch file

Are you seeing this error message?

XXX is not recognized as an internal or external command, operable program or batch file.

In short, it means you tried to run an executable that your OS (Operating System) couldn't find.

Updates.
25/07/2008 10:20:52 AM. Some extra detail added.
15/12/2008 12:27:42 AM. Fixed up formatting.
2/02/2009 12:52:00 PM. Corrected line continuation characters in Windows batch file excerpt.
16/05/2009 12:35:12 PM. Minor notes added. Note that Windows instructions were for "XP" or earlier.

Index

1. Executable Not Found
2. Executable?
3. Executable not found? But I installed it!
4. Get on the right PATH
5. Edit Windows PATH (XP and earlier) - for all users
6. Edit Windows PATH (XP and earlier) - for yourself only
7. Edit Linux Bash PATH - for all users
8. Edit Linux Bash PATH - for yourself only
9. Script based PATH - for a single run only

Executable Not Found

Are you seeing this error message?

XXX is not recognized as an internal or external command, operable program or batch file.

Substitute XXX for any command you are trying to run. For Java programmers, this will probably mean one of the following:

'java' is not recognized as an internal or external command, operable program or batch file.
'javac' is not recognized as an internal or external command, operable program or batch file.
'jar' is not recognized as an internal or external command, operable program or batch file.

In short, it means you tried to run an executable that your OS (Operating System) couldn't find. Windows outputs messages like the above. In Linux using Bash, the error messages would look like this:

Bash: java: command not found
Bash: javac: command not found
Bash: jar: command not found

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Executable?

An 'executable' is any file that can do something when it is run or 'executed' by the OS.

For example, consider the relationship between MS Word and MS Word files. C:\Program Files\Microsoft Office\OFFICE11\WINWORD.EXE is an executable. When a Windows OS runs this file, MS Word opens and you can create, edit and save Word files. C:\Temp\myPhoneNumbers.doc is not an executable. It is a Word file. By itself, this file cannot actually do anything - you have to open it with MS Word, the executable. So why can I open it just by double clicking on the Word document then? Because OSs are smart enough to recognise most documents by type. It knows the document is a Word document and opens Word, which then opens the documnt and allows you to work with it.

The same relationship holds true for Java class files and the Java executable, javac.exe. HelloWorld.class is not an executable. It cannot be run by the OS. The Java executable is javac.exe, C:\Program Files\Java\jdk1.6.0\bin\java.exe for example. When javac.exe is run by the Windows OS, it can take a Java class file and 'run' whatever instructions are inside it.

In Linux, an executable is usually a file that doesn't have an extension. So, java.exe will be just java. But the class and source files will still have the .class and .java extensions respectively.

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Executable not found? But I installed it!

If you get a message like these below, it means you tried to run an executable file that your OS couldn't find.

[Windows]
'java' is not recognized as an internal or external command, operable program or batch file.

[Linux - Bash]
Bash: java: command not found

There are two prime reasons why this happened. A) You didn't actually install it.. yeah right.. or B) even though you installed it, your OS still cannot find the file. Usually, the installation process does whatever is needed to ensure that your OS can find the file, but sometimes this doesn't work out and you have to fix it yourself.

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Get on the right PATH

Windows and Linux use a special system variable called "PATH" that tells them where all of their executable files are. The PATH variable actually contains a list of directories that the OS will search in order to find the executable you want to run. When you issue a command to the Windows OS (such as java or winword), it scans through the files in all of the directories in PATH until it finds a file whose name matches your command with a .exe extension added. Linux just looks for the file name: remember, it doesn't use the .exe extension for executables.

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Edit Windows PATH (XP and earlier) - for all users

The easiest way to fix this problem is to edit the System PATH variable, which means the change you make will affect all users on your Windows computer.

Go to your Windows desktop, right click on "My Computer" and select "Properties".

Click on the "Advanced" tab and press the "Environment Variables" button.

In the bottom half ("System variables"), scroll down until you see PATH. Click the "Edit" button and you can access the variable.

When I need to change it, I copy the value to a text editor, change it there, then copy and paste the new version back into the "Edit System Variable" dialog and press ok.

Here is the value of my PATH variable.

%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;C:\Program Files\IDM Computer Solutions\UltraEdit-32;C:\Program Files\QuickTime\QTSystem\

Unfortunately, nowhere in that list is a Java directory! Luckily, I know where I installed Java to: C:\Program Files\Java\jdk1.6.0. More importantly, if I look inside the bin directory of my Java installation - inside C:\Program Files\Java\jdk1.6.0\bin - I will find java.exe, javac.exe and jar.exe.

I need to edit my PATH to add the Java bin directory, preferably at the front, like so.

C:\Program Files\Java\jdk1.6.0\bin;%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;C:\Program Files\IDM Computer Solutions\UltraEdit-32;C:\Program Files\QuickTime\QTSystem\

Note 1: make sure all paths are separated with semi colons, i.e. ";".

Note 2: you can also use the DOS 8 character short form for directory names, such as what you see when issuing "DIR /X", e.g. "DOCUME~1" for "Documents and Settings".

Note 3: the list of directories is scanned in the order in which they appear in the PATH. So if you have two Java bin directories in a PATH (and both directories contain the executable), the first one will be used.

Warning: make sure you do not change any of the other entries in this list or you may end up breaking some other program.

Press OK and then OK again at the "Environment Variables" dialog. Of course, make sure to use the correct directory where Java was installed or this will not work! I then re-boot my computer - although any new DOS command window I open from this point will have the new version of the PATH.

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Edit Windows PATH (XP and earlier) - for yourself only

Sometimes you cannot or should not edit the System properties. Sometimes you don't want other users being able to execute their own Java code on your machine. If it is a shared or public machine, you may not even have the rights to edit these variables. In these cases, you can set the variable so that it only affects you.

Follow the same steps as above, except at the "Environment Variables" dialog, press "New" in the top half of "User variables for your username" This way, you can create your own variable named PATH and consisting solely of the Java bin directory. If by chance a local version already exists, edit this instead.

The local PATH is always added to the front of the global PATH, so your local entries will always be used (scanned) first.

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Edit Linux Bash PATH - for all users

For the Bash shell in Linux, you can edit the PATH by adding/editing the following 2 lines in your /etc/profile file:

PATH=$PATH:/usr/java/bin
export PATH

Note 1: make sure all paths are separated with colons, i.e. ":".

Note 2: the list of directories is scanned in the order in which they appear in the PATH. So if you have two Java bin directories in a PATH (and both directories contain the executable), the first one will be used.

Warning: make sure you do not change any of the other entries in this list (if the PATH line already exists) or you may end up breaking some other program.

Of course, make sure to use the correct directory where Java was installed or this will not work! Again, all new shells you open after you save the file will use the new PATH, but you should reboot your machine to make sure all programs already running start up fresh with the new PATH too.

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Edit Linux Bash PATH - for yourself only

Follow the same instructions as above, but do it in the ~/.Bash_profile instead - assuming you use the Bash shell. Other shells have their own "local" profile files, so you will need to find out what it is called and edit that instead.

The local PATH is always added to the front of the global PATH, so your local entries will always be used (scanned) first.

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Script based PATH - for a single run only

Sometimes there are good reasons why editing the PATH for yourself or all users isn't appropriate.

On a Windows machine, access rights might be locked down tight enough that you cannot even get to "My Computer" > right click > Properties. Alternatively, you may be writing a script (for Linux or Windows) that will be run on some one else's machine where you won't know for sure where Java is installed.

There is another way. You can write a script that will run your Java program for you - a .bat script for Windows, a .sh shell script for Linux. You then set your own PATH in the script before the lines that run the Java code. This version of the PATH will only affect your script and will not change PATH for any other users.

For example, I could write a batch file to create a jar file - using my own PATH - like this.

SET PATH=%PATH%;C:\Program Files\Java\jdk1.6.0\bin

jar cmf manifest.txt ^
HelloWorld.jar ^
org/bram/helloworld/*.java ^
org/bram/helloworld/*.class

The biggest advantage here is in terms of portability. You can make this script part of the files you copy over to other machines and just need to change PATH to make the script work. The biggest disadvantage is that you need extra effort to manage and write the script. Still, how much easier is it to manage a script than to manage someone else's System variables?

Thanks to Cody and Erik for asking me the question that inspired this post.