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# docs.GL

OpenGL 4
OpenGL 3
OpenGL ES 3

# glGetActiveUniformBlockName

## Name

glGetActiveUniformBlockName — retrieve the name of an active uniform block

## C Specification

`void glGetActiveUniformBlockName(` | GLuint program,
| GLuint uniformBlockIndex,
| GLsizei bufSize,
| GLsizei *length,
| GLchar *uniformBlockName`)`;

## Parameters

`program`

  Specifies the name of a program containing the uniform block.

`uniformBlockIndex`

  Specifies the index of the uniform block within `program`.

`bufSize`

  Specifies the size of the buffer addressed by `uniformBlockName`.

`length`

  Specifies the address of a variable to receive the number of characters that were written to `uniformBlockName`.

`uniformBlockName`

  Specifies the address an array of characters to receive the name of the uniform block at `uniformBlockIndex`.

## Description

`glGetActiveUniformBlockName` retrieves the name of the active uniform block at `uniformBlockIndex` within `program`.

`program` must be the name of a program object for which the command glLinkProgram must have been called in the past, although it is not required that glLinkProgram must have succeeded. The link could have failed because the number of active uniforms exceeded the limit.

`uniformBlockIndex` is an active uniform block index of `program`, and must be less than the value of `GL_ACTIVE_UNIFORM_BLOCKS`.

Upon success, the name of the uniform block identified by `unifomBlockIndex` is returned into `uniformBlockName`. The name is nul-terminated. The actual number of characters written into `uniformBlockName`, excluding the nul terminator, is returned in `length`. If `length` is `NULL`, no length is returned.

`bufSize` contains the maximum number of characters (including the nul terminator) that will be written into `uniformBlockName`.

If an error occurs, nothing will be written to `uniformBlockName` or `length`.

## Errors

`GL_INVALID_OPERATION` is generated if `program` is not the name of a program object for which glLinkProgram has been called in the past.

`GL_INVALID_VALUE` is generated if `uniformBlockIndex` is greater than or equal to the value of `GL_ACTIVE_UNIFORM_BLOCKS` or is not the index of an active uniform block in `program`.

## Notes

`glGetActiveUniformBlockName` is available only if the GL version is 3.1 or greater.

## See Also

glGetActiveUniformBlock, glGetUniformBlockIndex

## Copyright

Copyright © 2010 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. https://opencontent.org/openpub/.

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