## Name

glGetSubroutineIndex — retrieve the index of a subroutine uniform of a given shader stage within a program

## C Specification

`GLuint glGetSubroutineIndex(` | GLuint program,
| GLenum shadertype,
| const GLchar *name`)`;

## Parameters

`program`

  Specifies the name of the program containing shader stage.

`shadertype`

  Specifies the shader stage from which to query for subroutine uniform index. `shadertype` must be one of `GL_VERTEX_SHADER`, `GL_TESS_CONTROL_SHADER`, `GL_TESS_EVALUATION_SHADER`, `GL_GEOMETRY_SHADER` or `GL_FRAGMENT_SHADER`.

`name`

  Specifies the name of the subroutine uniform whose index to query.

## Description

`glGetSubroutineIndex` returns the index of a subroutine uniform within a shader stage attached to a program object. `program` contains the name of the program to which the shader is attached. `shadertype` specifies the stage from which to query shader subroutine index. `name` contains the null-terminated name of the subroutine uniform whose name to query.

If `name` is not the name of a subroutine uniform in the shader stage, `GL_INVALID_INDEX` is returned, but no error is generated. If `name` is the name of a subroutine uniform in the shader stage, a value between zero and the value of `GL_ACTIVE_SUBROUTINES` minus one will be returned. Subroutine indices are assigned using consecutive integers in the range from zero to the value of `GL_ACTIVE_SUBROUTINES` minus one for the shader stage.

## Errors

`GL_INVALID_ENUM` is generated if `shadertype` or `pname` is not one of the accepted values.

`GL_INVALID_VALUE` is generated if `program` is not the name of an existing program object.

## Version Support

| OpenGL Version
--- | ---
Function / Feature Name | 2.0 | 2.1 | 3.0 | 3.1 | 3.2 | 3.3 | 4.0 | 4.1 | 4.2 | 4.3 | 4.4 | 4.5
`glGetSubroutineIndex` | - | - | - | - | - | - | ✔ | ✔ | ✔ | ✔ | ✔ | ✔

## See Also

glGetProgram, glGetActiveSubroutineUniform, glGetActiveSubroutineUniformName

## Copyright

Copyright © 2010-2014 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. http://opencontent.org/openpub/.