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glGetProgram

Name

glGetProgramiv — Returns a parameter from a program object

C Specification

void glGetProgramiv( GLuint program,
GLenum pname,
GLint *params);

Parameters

program

Specifies the program object to be queried.

pname

Specifies the object parameter. Accepted symbolic names are GL_DELETE_STATUS, GL_LINK_STATUS, GL_VALIDATE_STATUS, GL_INFO_LOG_LENGTH, GL_ATTACHED_SHADERS, GL_ACTIVE_ATOMIC_COUNTER_BUFFERS, GL_ACTIVE_ATTRIBUTES, GL_ACTIVE_ATTRIBUTE_MAX_LENGTH, GL_ACTIVE_UNIFORMS, GL_ACTIVE_UNIFORM_BLOCKS, GL_ACTIVE_UNIFORM_BLOCK_MAX_NAME_LENGTH, GL_ACTIVE_UNIFORM_MAX_LENGTH, GL_COMPUTE_WORK_GROUP_SIZE, GL_PROGRAM_BINARY_LENGTH, GL_TRANSFORM_FEEDBACK_BUFFER_MODE, GL_TRANSFORM_FEEDBACK_VARYINGS, GL_TRANSFORM_FEEDBACK_VARYING_MAX_LENGTH, GL_GEOMETRY_VERTICES_OUT, GL_GEOMETRY_INPUT_TYPE, and GL_GEOMETRY_OUTPUT_TYPE.

params

Returns the requested object parameter.

Description

glGetProgram returns in params the value of a parameter for a specific program object. The following parameters are defined:

GL_DELETE_STATUS

params returns GL_TRUE if program is currently flagged for deletion, and GL_FALSE otherwise.

GL_LINK_STATUS

params returns GL_TRUE if the last link operation on program was successful, and GL_FALSE otherwise.

GL_VALIDATE_STATUS

params returns GL_TRUE or if the last validation operation on program was successful, and GL_FALSE otherwise.

GL_INFO_LOG_LENGTH

params returns the number of characters in the information log for program including the null termination character (i.e., the size of the character buffer required to store the information log). If program has no information log, a value of 0 is returned.

GL_ATTACHED_SHADERS

params returns the number of shader objects attached to program.

GL_ACTIVE_ATOMIC_COUNTER_BUFFERS

params returns the number of active attribute atomic counter buffers used by program.

GL_ACTIVE_ATTRIBUTES

params returns the number of active attribute variables for program.

GL_ACTIVE_ATTRIBUTE_MAX_LENGTH

params returns the length of the longest active attribute name for program, including the null termination character (i.e., the size of the character buffer required to store the longest attribute name). If no active attributes exist, 0 is returned.

GL_ACTIVE_UNIFORMS

params returns the number of active uniform variables for program.

GL_ACTIVE_UNIFORM_MAX_LENGTH

params returns the length of the longest active uniform variable name for program, including the null termination character (i.e., the size of the character buffer required to store the longest uniform variable name). If no active uniform variables exist, 0 is returned.

GL_PROGRAM_BINARY_LENGTH

params returns the length of the program binary, in bytes that will be returned by a call to glGetProgramBinary. When a progam's GL_LINK_STATUS is GL_FALSE, its program binary length is zero.

GL_COMPUTE_WORK_GROUP_SIZE

params returns an array of three integers containing the local work group size of the compute program as specified by its input layout qualifier(s). program must be the name of a program object that has been previously linked successfully and contains a binary for the compute shader stage.

GL_TRANSFORM_FEEDBACK_BUFFER_MODE

params returns a symbolic constant indicating the buffer mode used when transform feedback is active. This may be GL_SEPARATE_ATTRIBS or GL_INTERLEAVED_ATTRIBS.

GL_TRANSFORM_FEEDBACK_VARYINGS

params returns the number of varying variables to capture in transform feedback mode for the program.

GL_TRANSFORM_FEEDBACK_VARYING_MAX_LENGTH

params returns the length of the longest variable name to be used for transform feedback, including the null-terminator.

GL_GEOMETRY_VERTICES_OUT

params returns the maximum number of vertices that the geometry shader in program will output.

GL_GEOMETRY_INPUT_TYPE

params returns a symbolic constant indicating the primitive type accepted as input to the geometry shader contained in program.

GL_GEOMETRY_OUTPUT_TYPE

params returns a symbolic constant indicating the primitive type that will be output by the geometry shader contained in program.

Notes

GL_ACTIVE_UNIFORM_BLOCKS and GL_ACTIVE_UNIFORM_BLOCK_MAX_NAME_LENGTH are available only if the GL version 3.1 or greater.

GL_GEOMETRY_VERTICES_OUT, GL_GEOMETRY_INPUT_TYPE and GL_GEOMETRY_OUTPUT_TYPE are accepted only if the GL version is 3.2 or greater.

GL_COMPUTE_WORK_GROUP_SIZE is accepted only if the GL version is 4.3 or greater.

If an error is generated, no change is made to the contents of params.

Errors

GL_INVALID_VALUE is generated if program is not a value generated by OpenGL.

GL_INVALID_OPERATION is generated if program does not refer to a program object.

GL_INVALID_OPERATION is generated if pname is GL_GEOMETRY_VERTICES_OUT, GL_GEOMETRY_INPUT_TYPE, or GL_GEOMETRY_OUTPUT_TYPE, and program does not contain a geometry shader.

GL_INVALID_ENUM is generated if pname is not an accepted value.

GL_INVALID_OPERATION is generated if pname is GL_COMPUTE_WORK_GROUP_SIZE and program does not contain a binary for the compute shader stage.

Associated Gets

glGetActiveAttrib with argument program

glGetActiveUniform with argument program

glGetAttachedShaders with argument program

glGetProgramInfoLog with argument program

glIsProgram

Examples

Compile a program from a vertex shader and a fragment shader.
GLuint vshader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vshader, 1, &vertex_shader_source, NULL); // vertex_shader_source is a GLchar* containing glsl shader source code
glCompileShader(vshader);

GLint vertex_compiled;
glGetShaderiv(vshader, GL_COMPILE_STATUS, &vertex_compiled);
if (vertex_compiled != GL_TRUE)
{
    GLsizei log_length = 0;
    GLchar message[1024];
    glGetShaderInfoLog(vshader, 1024, &log_length, message);
    // Write the error to a log
}

GLuint fshader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fshader, 1, &fragment_shader_source, NULL); // fragment_shader_source is a GLchar* containing glsl shader source code
glCompileShader(fshader);

GLint fragment_compiled;
glGetShaderiv(fshader, GL_COMPILE_STATUS, &fragment_compiled);
if (fragment_compiled != GL_TRUE)
{
    GLsizei log_length = 0;
    GLchar message[1024];
    glGetShaderInfoLog(fshader, 1024, &log_length, message);
    // Write the error to a log
}

GLuint program = glCreateProgram();

// This step is unnecessary if you use the location specifier in your shader
// e.g. layout (location = 0) in vec3 position;
glBindAttribLocation(program, 0, "position"); // The index passed into glBindAttribLocation is
glBindAttribLocation(program, 1, "texcoord"); // used by glEnableVertexAttribArray. "position"
glBindAttribLocation(program, 2, "normal");   // "texcoord" "normal" and "color" are the names of the
glBindAttribLocation(program, 3, "color");    // respective inputs in your fragment shader.

glAttachShader(program, vshader);
glAttachShader(program, fshader);
glLinkProgram(program);

GLint program_linked;
glGetProgramiv(program, GL_LINK_STATUS, &program_linked);
if (program_linked != GL_TRUE)
{
    GLsizei log_length = 0;
    GLchar message[1024];
    glGetProgramInfoLog(program, 1024, &log_length, message);
    // Write the error to a log
}
Retrieve uniform data after the shader has been compiled
// The index returned from these GLint functions gets passed to glEnableVertexAttribArray during rendering.
GLint position_attrib_index = glGetAttribLocation(program, "position"); // program is what is returned by glCreateProgram.
GLint texcoord_attrib_index = glGetAttribLocation(program, "texcoord");
GLint normal_attrib_index = glGetAttribLocation(program, "normal");
GLint color_attrib_index = glGetAttribLocation(program, "color");

glBindFragDataLocation(program, 0, "output_color"); // "output_color" is an output value in your vertex shader and an input value in your fragment shader.

GLint num_uniforms;
glGetProgramiv(program, GL_ACTIVE_UNIFORMS, &num_uniforms);
GLchar uniform_name[256];
GLsizei length;
GLint size;
GLenum type;
for (int i = 0; i < num_uniforms; i++)
{
    glGetActiveUniform(program, i, sizeof(uniform_name), &length, &size, &type, uniform_name);
    // ... save this uniform data so it can be used during rendering
}

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
glGetProgramiv ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔
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