I have an external computer with an IP address like 100.12.5.7 and I would like to set a path to the environment variable like so:
setx MEDIA \\\100.12.5.7\d\media\
When I tried the above command, cmd prompt me that the variable is set successfully but when I do an echo %MEDIA%, it only shows me %MEDIA% instead of the full path. Any idea how I could fix this?
Setx doesn't affect the current console. Use Set and Setx together. Set, unlike Setx, requires an equal sign.
The reason setx can't affect the current console is that a copy of the starting program's environment is passed to programs it starts (usually Explorer's environment either direct or indirect via CMD). So all changes are local to that program. Setx sets registry keys, so only new programs can read them, and that really mean CMD.exe, as that rereads the registry keys.
Related
I have a one-line snippet that works perfectly in the command line, but fails and throws up errors when I run it as part of a batch script.
The below commands behaves as expected, deleting all empty subfolders in the folder.
for /f "delims=" %d in ('dir /s /b /ad ^| sort /r') do rd "%d"
However, when put in a batch file like so...
FOR /f "delims=" %%d in ('dir /s /b /ad ^| sort /r') do rd "%%d"
...it throws the standard error:
Sort is not recognised as an internal or external command
I've been experimenting for the last hour or so with and without escaping the pipe, changing the order of the options, looking up the documentation of both dir and sort, etc., but I've still not been able to figure out what's going on here. The rest of the batch file, which is only a few lines, works fine, and this is the only line in it that fails.
A) How does Windows command processor search for commands?
Windows command processor searches for a COMMAND to execute which
is not an internal command of cmd.exe and
is just specified with file name without file extension and without path
for a file matching the pattern command.* and having a file extension listed in local environment variable PATHEXT
first in current directory and
next in all directories of local environment variable PATH.
SORT and FIND and FINDSTR and ROBOCOPY and XCOPY and many more commands are not internal commands of cmd.exe. They are console applications installed with Windows located in directory %SystemRoot%\System32 having the file name sort.exe, find.exe, findstr.exe, robocopy.exe, xcopy.exe, ...
Such console applications available by default on Windows are called external commands to distinguish them better from console applications not installed with Windows operating system.
B) How is the environment variable PATH defined?
There are three types of PATH variables:
System PATH which is used for all accounts and stored in Windows registry under key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment
User PATH which is used only for current account and stored in Windows registry under key:
HKEY_CURRENT_USER\Environment
Local PATH which is always a copy of the local PATH of parent process which started the current process.
Windows concatenates system and user PATH to local PATH for the Windows Explorer instance used as Windows desktop with the shortcuts on the desktop screen and the Windows start menu and the Windows taskbar as visible interface for the user called Windows shell from which users usually start programs.
The entire currently active environment variables list of running process is copied for the new process by Windows on starting a new process. The Windows kernel library function CreateProcess does this environment variables list copy from the memory of the current process to the memory of the new process on function parameter lpEnvironment (long pointer to environment) being a null pointer. One of the CreateProcess functions is always used on Windows on starting an executable from another executable.
The parent process cannot modify the environment variables of any child process nor can a child process modify the environment variables of its parent process.
This means once a process like cmd.exe was started for execution of a batch file, the process has its own set of environment variables which only the process itself can modify. No other process can modify the environment variables of an already running process.
C) What does the error message mean?
The error message
'...' is not recognized as an internal or external command,operable program or batch file.
always means that
the file name of a
console application
GUI application
script (batch file, PowerShell script, Perl script, VBScript, JScript, ...)
was specified for execution most likely without file extension and without (complete) path to the executable/script file and
Windows failed to find a file matching the pattern FileName.* with a file extension listed in currently active environment variable PATHEXT in current directory or any other directory in currently active environment variable PATH.
D) What are the possible reasons for this error message?
Typical reasons are:
1. The file name of the file to execute was specified wrong due to a typing mistake.
Check character by character the name of the command/executable.
2. The current directory is different to the directory containing the file to execute.
Run echo Current directory is: %CD% on command line or add this line to the batch file above the command line which fails to see what the current directory is.
3. The executable or script to run is not installed at all.
Verify the existence of the executable to run. Some installation packages work only if other packages like Java, NPM, PHP, etc. were installed before.
4. The directory of the file to execute is not in PATH at all.
Open in Windows Control Panel the System settings window, click on Advanced system settings on left side, click on button Environment Variables and look in both lists for Path and their values. By default Path exists only in list of System variables.
5. A running process/application was not restarted after modification of system or user PATH.
A modification of system PATH or user PATH with command setx or via Control Panel – System and Security – System – Advanced system settings - Environment Variables was made by the user or an installer, but an already running process/application like an opened command prompt or PowerShell window was not closed/exited and opened/restarted after PATH modification. This is necessary as described in detail in chapter F) below.
6. An executable in %SystemRoot%\System32 is not found on 64-bit Windows.
There is the directory %SystemRoot%\System32 with 64-bit executables and %SystemRoot%\SysWOW64 with 32-bit executables on 64-bit Windows with a processor supporting also the x86 instruction set. Most executables exist in both directories. But there are some executables existing only in System32 and a few only in SysWOW64.
The system PATH contains by default as first folder path %SystemRoot%\System32. But which one of the two Windows system folders is searched for the executable specified without path or with the path %SystemRoot%\System32 depends on the execution environment. An application or script executed in 64-bit environment is really accessing %SystemRoot%\System32 while an application or script executed in 32-bit environment is redirected by the Windows file system redirector to the directory %SystemRoot%\SysWOW64.
An application or script running in 32-bit environment which wants to run a 64-bit executable in %SystemRoot%\System32 has to use the fully qualified file name of the executable with file path %SystemRoot%\Sysnative.
Note: %SystemRoot%\Sysnative is neither a directory nor any type of link. It is something very special existing only for x86 applications. It does not exist for amd64 applications. The condition if exist %SystemRoot%\Sysnative in a batch file is always false in both environments, but if exist %SystemRoot%\Sysnative\cmd.exe is true in 32-bit execution environment and false in 64-bit environment and also on 32-bit Windows. This condition can be used in batch scripts to find out if the batch file is processed by 32-bit cmd.exe in %SystemRoot%\SysWOW64 on 64-bit Windows which can be important to know depending on the task.
See also the Microsoft documentations WOW64 Implementation Details and Registry Keys Affected by WOW64.
7. PATH contains a reference to a not (yet) defined environment variable.
It is possible to specify in PATH a folder path using a reference to value of another environment variable like SystemRoot. It is important that this environment variable is also defined in same set of environment variables or a set of environment variables processed first by Windows.
For example if %JAVA_HOME%\bin is added to system PATH environment variable, there must be defined also a system environment variable JAVA_HOME with the base folder path to Java program files. It is not enough to have defined a user environment variable JAVA_HOME or define the environment variable JAVA_HOME later in the local environment of a batch file.
%JAVA_HOME%\bin added to user PATH is expanded by Windows to a full qualified folder path if the environment variable JAVA_HOME is defined either as system or as user environment variable, but not on JAVA_HOME defined later in the local environment of a Windows command process.
Such a mistake can be seen easily by opening a new command prompt window after making a modification on system or user PATH from Windows start menu and running set path. The output PATH should not contain anymore any %Variable% environment variable value reference.
8. The LOCAL variable PATH was modified before on command line or in batch file.
Run set path on command line or add this command to the batch file above the command line which fails to see the current values of the environment variables PATH and PATHEXT.
That reason is responsible for external command SORT not being found on execution of the batch file which contains somewhere above set path=....
9. LOCAL variable PATH is too long.
The local variable PATH of cmd.exe is too long. The Windows Command Processor fails to find any executable/script in the folder paths of local Path if the string value is longer than 8191 characters.
Please see my second answer here for more details regarding to length limitations of PATH.
Thanks goes to Albert Mosiałek for informing me about this cause of a not recognized program or script.
E) How to avoid this error message?
Best is coding a batch file for being independent on PATH and PATHEXT and the order of directories in PATH which means here using the command line:
FOR /f "delims=" %%d in ('dir /s /b /ad ^| %SystemRoot%\System32\sort.exe /r') do rd "%%d"
Any external command of which executable is stored in %SystemRoot%\System32 should be specified in a batch file with this path and with file extension .exe. Then Windows command interpreter does not need to search for a file using local PATH and PATHEXT and the batch file works always (as long as environment variable SystemRoot is not also modified in the batch file which I have never seen).
F) When is a system or user PATH change applied to processes?
When a user opens a command prompt window via Windows start menu or from within a Windows Explorer window, the user starts cmd.exe with implicit using option /K to keep the console window open after finishing a command which is good for debugging a batch file.
When a batch file is doubled clicked in Windows Explorer, the user starts cmd.exe for processing the batch file with implicit using option /C to close the console window after finishing batch processing which is not good for debugging a batch file as error messages cannot be seen in this case.
In both cases Windows creates a copy of the environment variables of the application starting cmd.exe which is usually Windows Explorer. Therefore the started command process has a local PATH of which value is the same as the parent process had on starting cmd.exe.
Example:
Open a command prompt window, run title Process1 and run set path.
Output is PATH and PATHEXT as currently defined for current user account in the console window having now the window title Process1.
Run set PATH=%SystemRoot%\System32 and next once again set path.
Output is again PATH and PATHEXT, but with PATH containing only one directory now.
Run start "Process2" and run in new console window with window title Process2 the command set path.
Output is PATH and PATHEXT with same values as before in Process1.
This demonstrates that on starting a new process the current environment variables of running process are copied and not what Windows itself has currently stored in Windows registry.
Run in Process2 the command set PATH= and next set path.
Output is only PATHEXT because local PATH does not exist anymore for Process2.
This demonstrates that every process can modify its environment variables including complete deletion.
Switch to Process1 window, run the command set PATH=%PATH%;%SystemRoot% and next set path.
Output is PATH with two directories and PATHEXT.
Run the command start "Process3" and in opened window with title Process3 the command set path.
Output is PATH with two directories as defined also for Process1 and PATHEXT.
Run in Process3 the command set PATH=%SystemRoot%\System32.
There are 3 command processes running with following values for local PATH when %SystemRoot% expands to C:\Windows:
Process1: PATH=C:\Windows\System32;C:\Windows
Process2: PATH does not exist at all.
Process3: PATH=C:\Windows\System32
So what happens now on opening Control Panel – System – Advanced System Settings – Environment Variables and adding to list of User variables the new environment variable PATH with value C:\Temp, or in case of there is already a user PATH environment variable, edit PATH and append ;C:\Temp to the value?
Well, as long as the dialog window with title Environment Variables showing the two lists is opened, nothing happens on modifying the variables, until button OK is clicked to take over all changes into Windows registry and close the window.
Let's go back to the three running command processes and run in Process1, Process2 and Process3 the command set path. It can be seen:
Process1: PATH=C:\Windows\System32;C:\Windows
Process2: PATH does not exist at all.
Process3: PATH=C:\Windows\System32
Nothing changed on already running processes.
No process can modify the environment variables of a different running process!
Open from Windows start menu one more command prompt window and run in fourth command process the command set path. It can be seen that local PATH of fourth command process has appended the directory C:\Temp now.
Then close all four command processes and delete the added user PATH respectively remove ;C:\Temp from user PATH if having appended this directory path before.
How is this possible if no process can modify the environment variables of an already running process?
How was the environment variables list of Windows Explorer instance running as Windows desktop modified on closing Environment Variables window with button OK?
The answer on those two questions was given by eryksun in his comment.
After writing the modifications on system and user variables into registry on clicking button OK of Environment Variables window, Windows sends the WM_SETTINGCHANGE message to all top-level windows to inform the running applications about changed system parameters.
It is up to the application if this event message is handled at all and how. Windows Explorer running as Windows desktop reads the environment variables from registry and updates its environment variables list accordingly. Other applications like Total Commander handle this message also and update their lists of environment variables too. But cmd.exe does not do that fortunately as this would be really problematic.
Is there any possibility to modify a system or user variable with notification via WM_SETTINGCHANGE from within a command prompt window or batch file?
It is possible to modify the registry value of an environment variable using reg add command. But this does not result in sending WM_SETTINGCHANGE message to all top-level windows. Such changes done with reg add or with regedit require a restart of Windows (or at least a log off and log on of current user) to be taken into account at all.
But there is also the command setx which is designed for modifying a system or user variable and which also sends the WM_SETTINGCHANGE message to all top-level windows after registry was updated according to specified arguments. Run setx /? in a command prompt window for details. But please take into account that setx does not modify the local environment variable of running command process. This must be done with using command set used in addition to setx.
G) How is environment variable PATHEXT handled by Windows?
The environment variable PATHEXT with the list of file extensions is handled by Windows different in comparison to environment variable PATH.
System PATHEXT and user PATHEXT are NOT concatenated to local PATHEXT.
A user PATHEXT replaces the system PATHEXT for all processes running under environment of the account having defined a user PATHEXT.
There is defined only a system PATHEXT environment variable by default.
H) Is it possible to disable file search in current directory?
Windows command processor searches by default in current directory if file name of a script file or executable is specified on command line or in a batch file without any path which means without a backslash \ (or a forward slash / thanks to auto-correction) in argument string.
But on Windows Vista and later Windows client versions and on Windows Server 2003 and later Windows server versions it is indeed possible to disable searching for a script/executable in current directory specified without at least relative path .\ by defining the environment variable NoDefaultCurrentDirectoryInExePath with any value as written by eryksun in his comment below and explained by Microsoft's documentation about function NeedCurrentDirectoryForExePathA.
See Removing the current working directory from the path for more details on usage of this environment variable.
I) How to modify system or user PATH?
The system and user PATH environment variables are modified by a user best using the Windows GUI dialog window Environment Variables. This dialog window can be opened as follows:
Click on the Windows Start menu button.
Type on keyboard environment variables.
There are offered by Windows the two items:
Edit the system environment variables
Edit environment variables for your account
Click on one of the two items to open the Environment Variables window.
There can be also opened the Windows Control Panel. There must be next clicked on System and Security with Category selected for display option View by. Next must be clicked System. There must be clicked on left side Advanced system settings and next on the button Environment Variables...
The System window can be opened also by pressing the key combination Windows logo key + Pause if the keyboard has the key Pause at all or at least in combination with the key Fn. See also the Microsoft documentation page Keyboard shortcuts in Windows.
The further user actions are self-explaining for editing either user Path in upper list on existing at all or system Path in lower list.
Most probably, you messed around with the PATH variable. Perhaps you are overwriting it somewhere else in your script. Since sort is an external command, opposed to all the others in your command line like for, dir, rd, which are cmd-internal commands, the PATH variable is needed to find the command. If PATH is not defined, external commands are searched in the current working directory only. There is also a PATHEXT variable that is needed to define standard file extensions for executables, like .com, .exe. So when sort appears in command prompt or in a batch file, the system searches the current working directory and all directories specified by the PATH variable for a file with the base name sort and one of the extensions specified by PATHEXT. The command sort is actually called sort.exe and is usually located in C:\Windows\System32.
In my case, I was so sure that I didn't mess with PATH. It was that I wasn't aware that path and PATH are the same. CMD is case insensitive.
This answer contains additional information to my first answer here regarding to length limitations of PATH.
There are not good coded executables/scripts which modify system or user PATH without checking first if the folder path to add is not already in string value of one of the two PATH environment variables as reported by Albert Mosiałek in a comment. Multiple executions of such a program results in local PATH string value of cmd.exe becomes longer and longer until reaching the PATH length limitations.
The maximum length of local PATH string value of cmd.exe depends on version of Windows and multiple string length limitations.
Length limitations of PATH on Windows Vista and Windows 7
Length limitations of system PATH
The system PATH as stored in Windows registry is truncated to its maximum length of 4095 characters before expanding all the environment variable references. The truncated string assigned to local PATH of cmd.exe can be also shorter than 4095 characters on system PATH contains environment variable references like %SystemRoot% (12 characters) expanding to C:\Windows (10 characters) and no user PATH is stored in Windows registry.
The system PATH is truncated to its maximum length of 4095 characters after expansion of the environment variable references. The truncated string assigned to local PATH of cmd.exe can be longer than the string value stored in Windows registry if environment variable references expand to strings which are longer than the environment variable reference strings.
In worst case the system PATH is truncated twice to a maximum length of 4095 characters, the first time before and the second time after expansion of the environment variable references.
Length limitations of user PATH
The user PATH is ignored completely independent on length of system PATH if the string value stored in Windows registry is longer than 4095 characters.
The user PATH is appended with an additional semicolon in expanded form to local PATH of cmd.exe on being in Windows registry not longer than 4095 characters even if the user PATH is in expanded form longer than 4095 characters because of environment variable references like %APPDATA%, %LOCALAPPDATA% or %USERPROFILE%.
The local PATH of cmd.exe can reach the maximum length of 8191 characters in worst case with a very long and perhaps already once or twice truncated system PATH and a user PATH not longer than 4095 characters in Windows registry, but longer than 4095 characters in expanded form.
The Windows Command Processor cmd.exe stops finding any executable on local PATH becomes too long, for example if the system PATH of 4095 characters in registry expands to a string with 4087 characters and is concatenated with a semicolon and a user Path stored in Windows registry with 4074 characters, but is expanded to a string value of length 4104 characters, resulting in a local Path with a total length of 8192 characters. There is not even found anymore any executable in %SystemRoot%\System32 on local PATH string value has a length of 8192 characters although the execution of set path outputs the local PATH with first directory path C:\Windows\System32.
There is the Command prompt (Cmd. exe) command-line string limitation which means that the environment variable name PATH plus equal sign = plus the variable string value plus the string terminating null byte must fit into a character array of 8192 characters. The string value of the local environment variable PATH as output on running set path in a command prompt window cannot be longer than 8186 characters for that reason although in memory the string value of local Path can be up to 8191 characters.
The internal command SET of cmd.exe does not output anymore a line-feed on running set path in a command prompt window if the local PATH has a string value of 8186 or more characters. In the console window is displayed for that reason in this case the environment variable PATHEXT with the equal sign and its string value appended to end of the string value of the environment variable PATH.
Length limitations of Control Panel windows for editing environment variables
A user or system PATH or any other in Windows registry persistent stored environment variable with a string value longer than 4094 characters is not displayed in the Environment Variables dialog window. For a user it looks like the environment variable does not exist which has a string value with more than 4094 characters although the environment variable is stored in registry and is perhaps even defined in local environment of running processes. The other user and system variables are still displayed in the Environment Variables window.
The Edit User Variable and Edit System Variable dialog windows display a Variable value with up to 4094 characters. A user can delete characters from such a long string value and save the shortened string value. But a user cannot append characters or replace existing characters on string value of the environment variable is longer than 2047 characters. A user can edit for that reason a user or system environment variable PATH with a string value longer than 2047 characters only for removal of a directory path using the Environment Variables window of Control Panel, but not for changing characters of an existing directory path or adding one more directory path to the environment variable string which is longer than 2047 characters.
Recommendations for PATH lengths
The system as well as the user PATH as stored in Windows registry and in their expanded form should be never longer than 4094 characters on Windows Vista and Windows 7 and are best both shorter than 2048 characters to be editable in the Control Panel windows.
Length limitations of PATH on Windows XP
Length limitations of system PATH
The system PATH as stored in Windows registry is truncated to its maximum length of 2047 characters before expanding all the environment variable references. The truncated string assigned to local PATH of cmd.exe can be also shorter than 2047 characters on system PATH contains environment variable references like %SystemRoot% (12 characters) expanding to C:\Windows (10 characters) and no user PATH is stored in Windows registry.
The system PATH is truncated to its maximum length of 2047 characters after expansion of the environment variable references. The truncated string assigned to local PATH of cmd.exe can be longer than the string value stored in Windows registry if environment variable references expand to strings which are longer than the environment variable reference strings.
In worst case the system PATH is truncated twice to a maximum length of 2047 characters, the first time before and the second time after expansion of the environment variable references.
Length limitations of user PATH
The user PATH is ignored completely if the expanded system PATH concatenated with the expanded user PATH with an additionally inserted semicolon results in a string value longer than 2047 characters. The maximum length of the user PATH on Windows XP depends for that reason on current length of expanded system PATH.
Length limitations of Control Panel windows for editing environment variables
A user or system PATH or any other in Windows registry persistent stored environment variable with a string value longer than 4095 characters is not displayed in the Environment Variables dialog window. For a user it looks like the environment variable does not exist which has a string value of more than 4095 characters although the environment variable is stored in registry and is perhaps even defined truncated in the local environment of running processes. The other user and system variables are still displayed in the Environment Variables window.
The Edit User Variable and Edit System Variable dialog windows display a Variable value with up to 2047 characters. A user can edit an even longer string value and save the string value, but the string value is always truncated to a maximum length of 2047 characters as displayed in edit field of the window. A user cannot append characters or replace existing characters on string value of the environment variable is longer than 2047 characters.
Recommendations for PATH lengths
The system PATH as stored in Windows registry and in its expanded form should be never longer than 2047 characters on Windows XP.
The user PATH in its expanded form should be short enough to be not ignored on concatenating it with the system PATH.
I have a one-line snippet that works perfectly in the command line, but fails and throws up errors when I run it as part of a batch script.
The below commands behaves as expected, deleting all empty subfolders in the folder.
for /f "delims=" %d in ('dir /s /b /ad ^| sort /r') do rd "%d"
However, when put in a batch file like so...
FOR /f "delims=" %%d in ('dir /s /b /ad ^| sort /r') do rd "%%d"
...it throws the standard error:
Sort is not recognised as an internal or external command
I've been experimenting for the last hour or so with and without escaping the pipe, changing the order of the options, looking up the documentation of both dir and sort, etc., but I've still not been able to figure out what's going on here. The rest of the batch file, which is only a few lines, works fine, and this is the only line in it that fails.
A) How does Windows command processor search for commands?
Windows command processor searches for a COMMAND to execute which
is not an internal command of cmd.exe and
is just specified with file name without file extension and without path
for a file matching the pattern command.* and having a file extension listed in local environment variable PATHEXT
first in current directory and
next in all directories of local environment variable PATH.
SORT and FIND and FINDSTR and ROBOCOPY and XCOPY and many more commands are not internal commands of cmd.exe. They are console applications installed with Windows located in directory %SystemRoot%\System32 having the file name sort.exe, find.exe, findstr.exe, robocopy.exe, xcopy.exe, ...
Such console applications available by default on Windows are called external commands to distinguish them better from console applications not installed with Windows operating system.
B) How is the environment variable PATH defined?
There are three types of PATH variables:
System PATH which is used for all accounts and stored in Windows registry under key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment
User PATH which is used only for current account and stored in Windows registry under key:
HKEY_CURRENT_USER\Environment
Local PATH which is always a copy of the local PATH of parent process which started the current process.
Windows concatenates system and user PATH to local PATH for the Windows Explorer instance used as Windows desktop with the shortcuts on the desktop screen and the Windows start menu and the Windows taskbar as visible interface for the user called Windows shell from which users usually start programs.
The entire currently active environment variables list of running process is copied for the new process by Windows on starting a new process. The Windows kernel library function CreateProcess does this environment variables list copy from the memory of the current process to the memory of the new process on function parameter lpEnvironment (long pointer to environment) being a null pointer. One of the CreateProcess functions is always used on Windows on starting an executable from another executable.
The parent process cannot modify the environment variables of any child process nor can a child process modify the environment variables of its parent process.
This means once a process like cmd.exe was started for execution of a batch file, the process has its own set of environment variables which only the process itself can modify. No other process can modify the environment variables of an already running process.
C) What does the error message mean?
The error message
'...' is not recognized as an internal or external command,operable program or batch file.
always means that
the file name of a
console application
GUI application
script (batch file, PowerShell script, Perl script, VBScript, JScript, ...)
was specified for execution most likely without file extension and without (complete) path to the executable/script file and
Windows failed to find a file matching the pattern FileName.* with a file extension listed in currently active environment variable PATHEXT in current directory or any other directory in currently active environment variable PATH.
D) What are the possible reasons for this error message?
Typical reasons are:
1. The file name of the file to execute was specified wrong due to a typing mistake.
Check character by character the name of the command/executable.
2. The current directory is different to the directory containing the file to execute.
Run echo Current directory is: %CD% on command line or add this line to the batch file above the command line which fails to see what the current directory is.
3. The executable or script to run is not installed at all.
Verify the existence of the executable to run. Some installation packages work only if other packages like Java, NPM, PHP, etc. were installed before.
4. The directory of the file to execute is not in PATH at all.
Open in Windows Control Panel the System settings window, click on Advanced system settings on left side, click on button Environment Variables and look in both lists for Path and their values. By default Path exists only in list of System variables.
5. A running process/application was not restarted after modification of system or user PATH.
A modification of system PATH or user PATH with command setx or via Control Panel – System and Security – System – Advanced system settings - Environment Variables was made by the user or an installer, but an already running process/application like an opened command prompt or PowerShell window was not closed/exited and opened/restarted after PATH modification. This is necessary as described in detail in chapter F) below.
6. An executable in %SystemRoot%\System32 is not found on 64-bit Windows.
There is the directory %SystemRoot%\System32 with 64-bit executables and %SystemRoot%\SysWOW64 with 32-bit executables on 64-bit Windows with a processor supporting also the x86 instruction set. Most executables exist in both directories. But there are some executables existing only in System32 and a few only in SysWOW64.
The system PATH contains by default as first folder path %SystemRoot%\System32. But which one of the two Windows system folders is searched for the executable specified without path or with the path %SystemRoot%\System32 depends on the execution environment. An application or script executed in 64-bit environment is really accessing %SystemRoot%\System32 while an application or script executed in 32-bit environment is redirected by the Windows file system redirector to the directory %SystemRoot%\SysWOW64.
An application or script running in 32-bit environment which wants to run a 64-bit executable in %SystemRoot%\System32 has to use the fully qualified file name of the executable with file path %SystemRoot%\Sysnative.
Note: %SystemRoot%\Sysnative is neither a directory nor any type of link. It is something very special existing only for x86 applications. It does not exist for amd64 applications. The condition if exist %SystemRoot%\Sysnative in a batch file is always false in both environments, but if exist %SystemRoot%\Sysnative\cmd.exe is true in 32-bit execution environment and false in 64-bit environment and also on 32-bit Windows. This condition can be used in batch scripts to find out if the batch file is processed by 32-bit cmd.exe in %SystemRoot%\SysWOW64 on 64-bit Windows which can be important to know depending on the task.
See also the Microsoft documentations WOW64 Implementation Details and Registry Keys Affected by WOW64.
7. PATH contains a reference to a not (yet) defined environment variable.
It is possible to specify in PATH a folder path using a reference to value of another environment variable like SystemRoot. It is important that this environment variable is also defined in same set of environment variables or a set of environment variables processed first by Windows.
For example if %JAVA_HOME%\bin is added to system PATH environment variable, there must be defined also a system environment variable JAVA_HOME with the base folder path to Java program files. It is not enough to have defined a user environment variable JAVA_HOME or define the environment variable JAVA_HOME later in the local environment of a batch file.
%JAVA_HOME%\bin added to user PATH is expanded by Windows to a full qualified folder path if the environment variable JAVA_HOME is defined either as system or as user environment variable, but not on JAVA_HOME defined later in the local environment of a Windows command process.
Such a mistake can be seen easily by opening a new command prompt window after making a modification on system or user PATH from Windows start menu and running set path. The output PATH should not contain anymore any %Variable% environment variable value reference.
8. The LOCAL variable PATH was modified before on command line or in batch file.
Run set path on command line or add this command to the batch file above the command line which fails to see the current values of the environment variables PATH and PATHEXT.
That reason is responsible for external command SORT not being found on execution of the batch file which contains somewhere above set path=....
9. LOCAL variable PATH is too long.
The local variable PATH of cmd.exe is too long. The Windows Command Processor fails to find any executable/script in the folder paths of local Path if the string value is longer than 8191 characters.
Please see my second answer here for more details regarding to length limitations of PATH.
Thanks goes to Albert Mosiałek for informing me about this cause of a not recognized program or script.
E) How to avoid this error message?
Best is coding a batch file for being independent on PATH and PATHEXT and the order of directories in PATH which means here using the command line:
FOR /f "delims=" %%d in ('dir /s /b /ad ^| %SystemRoot%\System32\sort.exe /r') do rd "%%d"
Any external command of which executable is stored in %SystemRoot%\System32 should be specified in a batch file with this path and with file extension .exe. Then Windows command interpreter does not need to search for a file using local PATH and PATHEXT and the batch file works always (as long as environment variable SystemRoot is not also modified in the batch file which I have never seen).
F) When is a system or user PATH change applied to processes?
When a user opens a command prompt window via Windows start menu or from within a Windows Explorer window, the user starts cmd.exe with implicit using option /K to keep the console window open after finishing a command which is good for debugging a batch file.
When a batch file is doubled clicked in Windows Explorer, the user starts cmd.exe for processing the batch file with implicit using option /C to close the console window after finishing batch processing which is not good for debugging a batch file as error messages cannot be seen in this case.
In both cases Windows creates a copy of the environment variables of the application starting cmd.exe which is usually Windows Explorer. Therefore the started command process has a local PATH of which value is the same as the parent process had on starting cmd.exe.
Example:
Open a command prompt window, run title Process1 and run set path.
Output is PATH and PATHEXT as currently defined for current user account in the console window having now the window title Process1.
Run set PATH=%SystemRoot%\System32 and next once again set path.
Output is again PATH and PATHEXT, but with PATH containing only one directory now.
Run start "Process2" and run in new console window with window title Process2 the command set path.
Output is PATH and PATHEXT with same values as before in Process1.
This demonstrates that on starting a new process the current environment variables of running process are copied and not what Windows itself has currently stored in Windows registry.
Run in Process2 the command set PATH= and next set path.
Output is only PATHEXT because local PATH does not exist anymore for Process2.
This demonstrates that every process can modify its environment variables including complete deletion.
Switch to Process1 window, run the command set PATH=%PATH%;%SystemRoot% and next set path.
Output is PATH with two directories and PATHEXT.
Run the command start "Process3" and in opened window with title Process3 the command set path.
Output is PATH with two directories as defined also for Process1 and PATHEXT.
Run in Process3 the command set PATH=%SystemRoot%\System32.
There are 3 command processes running with following values for local PATH when %SystemRoot% expands to C:\Windows:
Process1: PATH=C:\Windows\System32;C:\Windows
Process2: PATH does not exist at all.
Process3: PATH=C:\Windows\System32
So what happens now on opening Control Panel – System – Advanced System Settings – Environment Variables and adding to list of User variables the new environment variable PATH with value C:\Temp, or in case of there is already a user PATH environment variable, edit PATH and append ;C:\Temp to the value?
Well, as long as the dialog window with title Environment Variables showing the two lists is opened, nothing happens on modifying the variables, until button OK is clicked to take over all changes into Windows registry and close the window.
Let's go back to the three running command processes and run in Process1, Process2 and Process3 the command set path. It can be seen:
Process1: PATH=C:\Windows\System32;C:\Windows
Process2: PATH does not exist at all.
Process3: PATH=C:\Windows\System32
Nothing changed on already running processes.
No process can modify the environment variables of a different running process!
Open from Windows start menu one more command prompt window and run in fourth command process the command set path. It can be seen that local PATH of fourth command process has appended the directory C:\Temp now.
Then close all four command processes and delete the added user PATH respectively remove ;C:\Temp from user PATH if having appended this directory path before.
How is this possible if no process can modify the environment variables of an already running process?
How was the environment variables list of Windows Explorer instance running as Windows desktop modified on closing Environment Variables window with button OK?
The answer on those two questions was given by eryksun in his comment.
After writing the modifications on system and user variables into registry on clicking button OK of Environment Variables window, Windows sends the WM_SETTINGCHANGE message to all top-level windows to inform the running applications about changed system parameters.
It is up to the application if this event message is handled at all and how. Windows Explorer running as Windows desktop reads the environment variables from registry and updates its environment variables list accordingly. Other applications like Total Commander handle this message also and update their lists of environment variables too. But cmd.exe does not do that fortunately as this would be really problematic.
Is there any possibility to modify a system or user variable with notification via WM_SETTINGCHANGE from within a command prompt window or batch file?
It is possible to modify the registry value of an environment variable using reg add command. But this does not result in sending WM_SETTINGCHANGE message to all top-level windows. Such changes done with reg add or with regedit require a restart of Windows (or at least a log off and log on of current user) to be taken into account at all.
But there is also the command setx which is designed for modifying a system or user variable and which also sends the WM_SETTINGCHANGE message to all top-level windows after registry was updated according to specified arguments. Run setx /? in a command prompt window for details. But please take into account that setx does not modify the local environment variable of running command process. This must be done with using command set used in addition to setx.
G) How is environment variable PATHEXT handled by Windows?
The environment variable PATHEXT with the list of file extensions is handled by Windows different in comparison to environment variable PATH.
System PATHEXT and user PATHEXT are NOT concatenated to local PATHEXT.
A user PATHEXT replaces the system PATHEXT for all processes running under environment of the account having defined a user PATHEXT.
There is defined only a system PATHEXT environment variable by default.
H) Is it possible to disable file search in current directory?
Windows command processor searches by default in current directory if file name of a script file or executable is specified on command line or in a batch file without any path which means without a backslash \ (or a forward slash / thanks to auto-correction) in argument string.
But on Windows Vista and later Windows client versions and on Windows Server 2003 and later Windows server versions it is indeed possible to disable searching for a script/executable in current directory specified without at least relative path .\ by defining the environment variable NoDefaultCurrentDirectoryInExePath with any value as written by eryksun in his comment below and explained by Microsoft's documentation about function NeedCurrentDirectoryForExePathA.
See Removing the current working directory from the path for more details on usage of this environment variable.
I) How to modify system or user PATH?
The system and user PATH environment variables are modified by a user best using the Windows GUI dialog window Environment Variables. This dialog window can be opened as follows:
Click on the Windows Start menu button.
Type on keyboard environment variables.
There are offered by Windows the two items:
Edit the system environment variables
Edit environment variables for your account
Click on one of the two items to open the Environment Variables window.
There can be also opened the Windows Control Panel. There must be next clicked on System and Security with Category selected for display option View by. Next must be clicked System. There must be clicked on left side Advanced system settings and next on the button Environment Variables...
The System window can be opened also by pressing the key combination Windows logo key + Pause if the keyboard has the key Pause at all or at least in combination with the key Fn. See also the Microsoft documentation page Keyboard shortcuts in Windows.
The further user actions are self-explaining for editing either user Path in upper list on existing at all or system Path in lower list.
Most probably, you messed around with the PATH variable. Perhaps you are overwriting it somewhere else in your script. Since sort is an external command, opposed to all the others in your command line like for, dir, rd, which are cmd-internal commands, the PATH variable is needed to find the command. If PATH is not defined, external commands are searched in the current working directory only. There is also a PATHEXT variable that is needed to define standard file extensions for executables, like .com, .exe. So when sort appears in command prompt or in a batch file, the system searches the current working directory and all directories specified by the PATH variable for a file with the base name sort and one of the extensions specified by PATHEXT. The command sort is actually called sort.exe and is usually located in C:\Windows\System32.
In my case, I was so sure that I didn't mess with PATH. It was that I wasn't aware that path and PATH are the same. CMD is case insensitive.
This answer contains additional information to my first answer here regarding to length limitations of PATH.
There are not good coded executables/scripts which modify system or user PATH without checking first if the folder path to add is not already in string value of one of the two PATH environment variables as reported by Albert Mosiałek in a comment. Multiple executions of such a program results in local PATH string value of cmd.exe becomes longer and longer until reaching the PATH length limitations.
The maximum length of local PATH string value of cmd.exe depends on version of Windows and multiple string length limitations.
Length limitations of PATH on Windows Vista and Windows 7
Length limitations of system PATH
The system PATH as stored in Windows registry is truncated to its maximum length of 4095 characters before expanding all the environment variable references. The truncated string assigned to local PATH of cmd.exe can be also shorter than 4095 characters on system PATH contains environment variable references like %SystemRoot% (12 characters) expanding to C:\Windows (10 characters) and no user PATH is stored in Windows registry.
The system PATH is truncated to its maximum length of 4095 characters after expansion of the environment variable references. The truncated string assigned to local PATH of cmd.exe can be longer than the string value stored in Windows registry if environment variable references expand to strings which are longer than the environment variable reference strings.
In worst case the system PATH is truncated twice to a maximum length of 4095 characters, the first time before and the second time after expansion of the environment variable references.
Length limitations of user PATH
The user PATH is ignored completely independent on length of system PATH if the string value stored in Windows registry is longer than 4095 characters.
The user PATH is appended with an additional semicolon in expanded form to local PATH of cmd.exe on being in Windows registry not longer than 4095 characters even if the user PATH is in expanded form longer than 4095 characters because of environment variable references like %APPDATA%, %LOCALAPPDATA% or %USERPROFILE%.
The local PATH of cmd.exe can reach the maximum length of 8191 characters in worst case with a very long and perhaps already once or twice truncated system PATH and a user PATH not longer than 4095 characters in Windows registry, but longer than 4095 characters in expanded form.
The Windows Command Processor cmd.exe stops finding any executable on local PATH becomes too long, for example if the system PATH of 4095 characters in registry expands to a string with 4087 characters and is concatenated with a semicolon and a user Path stored in Windows registry with 4074 characters, but is expanded to a string value of length 4104 characters, resulting in a local Path with a total length of 8192 characters. There is not even found anymore any executable in %SystemRoot%\System32 on local PATH string value has a length of 8192 characters although the execution of set path outputs the local PATH with first directory path C:\Windows\System32.
There is the Command prompt (Cmd. exe) command-line string limitation which means that the environment variable name PATH plus equal sign = plus the variable string value plus the string terminating null byte must fit into a character array of 8192 characters. The string value of the local environment variable PATH as output on running set path in a command prompt window cannot be longer than 8186 characters for that reason although in memory the string value of local Path can be up to 8191 characters.
The internal command SET of cmd.exe does not output anymore a line-feed on running set path in a command prompt window if the local PATH has a string value of 8186 or more characters. In the console window is displayed for that reason in this case the environment variable PATHEXT with the equal sign and its string value appended to end of the string value of the environment variable PATH.
Length limitations of Control Panel windows for editing environment variables
A user or system PATH or any other in Windows registry persistent stored environment variable with a string value longer than 4094 characters is not displayed in the Environment Variables dialog window. For a user it looks like the environment variable does not exist which has a string value with more than 4094 characters although the environment variable is stored in registry and is perhaps even defined in local environment of running processes. The other user and system variables are still displayed in the Environment Variables window.
The Edit User Variable and Edit System Variable dialog windows display a Variable value with up to 4094 characters. A user can delete characters from such a long string value and save the shortened string value. But a user cannot append characters or replace existing characters on string value of the environment variable is longer than 2047 characters. A user can edit for that reason a user or system environment variable PATH with a string value longer than 2047 characters only for removal of a directory path using the Environment Variables window of Control Panel, but not for changing characters of an existing directory path or adding one more directory path to the environment variable string which is longer than 2047 characters.
Recommendations for PATH lengths
The system as well as the user PATH as stored in Windows registry and in their expanded form should be never longer than 4094 characters on Windows Vista and Windows 7 and are best both shorter than 2048 characters to be editable in the Control Panel windows.
Length limitations of PATH on Windows XP
Length limitations of system PATH
The system PATH as stored in Windows registry is truncated to its maximum length of 2047 characters before expanding all the environment variable references. The truncated string assigned to local PATH of cmd.exe can be also shorter than 2047 characters on system PATH contains environment variable references like %SystemRoot% (12 characters) expanding to C:\Windows (10 characters) and no user PATH is stored in Windows registry.
The system PATH is truncated to its maximum length of 2047 characters after expansion of the environment variable references. The truncated string assigned to local PATH of cmd.exe can be longer than the string value stored in Windows registry if environment variable references expand to strings which are longer than the environment variable reference strings.
In worst case the system PATH is truncated twice to a maximum length of 2047 characters, the first time before and the second time after expansion of the environment variable references.
Length limitations of user PATH
The user PATH is ignored completely if the expanded system PATH concatenated with the expanded user PATH with an additionally inserted semicolon results in a string value longer than 2047 characters. The maximum length of the user PATH on Windows XP depends for that reason on current length of expanded system PATH.
Length limitations of Control Panel windows for editing environment variables
A user or system PATH or any other in Windows registry persistent stored environment variable with a string value longer than 4095 characters is not displayed in the Environment Variables dialog window. For a user it looks like the environment variable does not exist which has a string value of more than 4095 characters although the environment variable is stored in registry and is perhaps even defined truncated in the local environment of running processes. The other user and system variables are still displayed in the Environment Variables window.
The Edit User Variable and Edit System Variable dialog windows display a Variable value with up to 2047 characters. A user can edit an even longer string value and save the string value, but the string value is always truncated to a maximum length of 2047 characters as displayed in edit field of the window. A user cannot append characters or replace existing characters on string value of the environment variable is longer than 2047 characters.
Recommendations for PATH lengths
The system PATH as stored in Windows registry and in its expanded form should be never longer than 2047 characters on Windows XP.
The user PATH in its expanded form should be short enough to be not ignored on concatenating it with the system PATH.
On my Pc, running Windows XP 5.1.2600, following
"My Computer" > "Properties" > "Advanced" > "Environment Variables" > "Path"
I get a string, but in a batch file, or directly typing from prompt, by means of
echo %path%
I get a different one.
Can someone, please, explain what makes them differ and how to fix the issue, setting the "DOS-path" to the same value of "Windows-PATH" ?
Two things:
As others have mentioned, the full value of PATH is the combination of the user's PATH variable and the system's PATH variable.
If you change environment variables (including PATH), any processes already running (including the Command Prompt) will continue using the old environment variable values. You will need to restart those processes to pick up any changes that you've made.
The value of the PATH environment variable you see on the command line (which has nothing to do with "DOS" btw) is the sum of the system wide PATH variable and the user specific PATH variable.
If you open the dialog with the system variables from within the control panel, the upper part contains the user specific environment variables. The lower part contains the system variables.
If you set a PATH variable for your user to e.g. c:\foo, and the system path is be c:\Windows\System32 then you'd see c:\Windows\System32;c:\foo when you do an ECHO %PATH% on the commandline.
Probably the difference you are seeing is that when a new process is made, its default environment contains a PATH variable that is made by merging the system variable with the user variable.
As for how to "fix the issue", there is nothing to fix. The system behaves as designed.
I was getting the same issue where the System Variable that I get through the
"My Computer" > "Properties" > "Advanced" > "Environment Variables" >
"Path"
was different that the one being displayed through the command line interface via
ECHO %PATH%
The fix for this is basically to wait for the change to take place and this can be made faster by restarting the cmd and explorer. To do that you can simply end task for Explorer and CMD and then start a new task or restart it directly.
The same shall be done for the CMD as well.
The Windows registry can hold path entries that do not show up in the Environment Variables version of PATH you see via the control panel. (Why, I do not know).
The difference means that something (likely an install script) made changes to the registry.
To view or change the local user's path variable, look in the HKEY_CURRENT_USER\Environment key.
To view the system path, look in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment
I tried to add to the PATH environment variable ";C:\my_EXE" so I can run the programs I put there via cmd (windows 8).
I tried this command:
set PATH=%PATH%;C:\my_EXE
but it changed the PATH environment variable only until the CMD window was closed.
I searched on Google and I found this command:
setx PATH "%PATH%;C:\my_EXE"
that is supposed to set it forever, but it also works only until the CMD window has closed
and it made something like this:
[new PATH]=[old PATH]X2
It appears only in a new cmd and not in system properties(!=cmd, there is the PATH with my new path and not X2)
Why does this happen?
How can I set the PATH environment variable without problems?
There are two persistent PATH variables, the per-machine variable and the per-user one. They get appended together to produce the actual environment variable. (Environment variables in the PATH are also expanded at this point.)
That's why you're getting the path doubled up, because you've set the per-user persistent variable to include everything from the environment variable (which already includes everything from the per-machine persistent one).
You can use setx with the /m parameter to set the per-machine persistent variable, but this isn't ideal:
If the per-user persistent variable is set, its contents will be copied into the per-machine persistent variable, which is likely to be inappropriate;
If the persistent variable references other environment variables, the references will be replaced with the current value of those variables. If the referenced variables change, the PATH will no longer follow those changes. (To be honest, though, most of the time this won't matter: the feature isn't commonly used.)
Instead, consider using pathman which is specifically designed to manipulate paths. You can get pathman.exe from the Windows Server 2003 Resource Kit Tools download.
Note that both setx and pathman may hang if there are any unresponsive GUI applications running, even if the application window is hidden. The best way to minimize this risk is to reboot the machine immediately before running any script that uses setx or pathman.
You should use setx command with "/m" parameter.
i need to set permanently the %username% variable on windows is that possible?
I mean if I do on command prompt set username=UPPERCASE I can see that the variable is changed, however as expected this does work just in that command prompt, If I open another one the username variable is the original.
I tried to find the correspondent registry value but I did not find it.
I need some automatic way to do it.
Thanks!
When each process starts, the process gets a copy of the parent process' environment variables. So, if you used Windows Explorer to start your command prompt. You get a copy of Explorer.exe's environment variables, but when you edit it in cmd.exe, you don't edit the value for the rest of the system.
That said, Windows provides an event that processes can subscribe to so they can be told that there is a new value for environment variables. If you are interested, I can try to dig it up. I've used it before for the Path environment variable and think it may apply to your problem.
Sounds like you should create a bat file. This will prompt the user for their username and put it in the %USERNAME% environment variable.
SET /p USERNAME=What is your UserName?
putty /user:%username%