GetEnvironmentVariableA function (processenv.h)

Retrieves the contents of the specified variable from the environment block of the calling process.


DWORD GetEnvironmentVariableA(
  [in, optional]  LPCSTR lpName,
  [out, optional] LPSTR  lpBuffer,
  [in]            DWORD  nSize


[in, optional] lpName

The name of the environment variable.

[out, optional] lpBuffer

A pointer to a buffer that receives the contents of the specified environment variable as a null-terminated string. An environment variable has a maximum size limit of 32,767 characters, including the null-terminating character.

[in] nSize

The size of the buffer pointed to by the lpBuffer parameter, including the null-terminating character, in characters.

Return value

If the function succeeds, the return value is the number of characters stored in the buffer pointed to by lpBuffer, not including the terminating null character.

If lpBuffer is not large enough to hold the data, the return value is the buffer size, in characters, required to hold the string and its terminating null character and the contents of lpBuffer are undefined.

If the function fails, the return value is zero. If the specified environment variable was not found in the environment block, GetLastError returns ERROR_ENVVAR_NOT_FOUND.


This function can retrieve either a system environment variable or a user environment variable.


For an example, see Changing Environment Variables.


The processenv.h header defines GetEnvironmentVariable as an alias which automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.


Requirement Value
Minimum supported client Windows XP [desktop apps | UWP apps]
Minimum supported server Windows Server 2003 [desktop apps | UWP apps]
Target Platform Windows
Header processenv.h (include Windows.h on Windows Server 2003, Windows Vista, Windows 7, Windows Server 2008 Windows Server 2008 R2)
Library Kernel32.lib
DLL Kernel32.dll

See also

Environment Variables