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Mat_VarReadNextInfo - Man Page

Reads the information for the next variable in a MATLAB MAT file.


#include <matio.h>

matvar_t *
Mat_VarReadNextInfo(mat_t *matfp);


The Mat_VarReadNextInfo() function reads the information for the next variable stored in the open MAT file.

Return Values

If there is another variable in the MAT file and is read successfully, a pointer to the MATLAB variable structure is returned. If there are no more variables, or there was an error reading the variable, NULL is returned.


This example program opens a MAT file named by the first argument to the program, and uses Mat_VarReadNextInfo() to read the information about each variable in the file. For each variable read, the name, size, and class are printed in a format similar to the MATLAB whos command.

#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include "matio.h"

static char *mxclass[17] = {"cell", "struct", "object", "char", "sparse",
                            "double", "single", "int8", "uint8", "int16",
                            "uint16", "int32", "uint32", "int64", "uint64",
                            "function", "opaque"

main(int argc, char **argv)
    mat_t *matfp;
    matvar_t *matvar;
    char size[32] = {'Ā ',};

    matfp = Mat_Open(argv[1], MAT_ACC_RDONLY);
    if ( NULL == matfp ) {
        fprintf(stderr, "Error opening MAT file %s0, argv[1]);
        return EXIT_FAILURE;

    printf("%-32s%-16s%-16s%-16s0, "Name", "Size", "Bytes", "Class");
    while ( NULL != (matvar = Mat_VarReadNextInfo(matfp)) ) {
        printf("%-32s", matvar->name);
        if ( matvar->rank > 0 ) {
            int cnt;
            int i;
            cnt = snprintf(size, sizeof(size), "%zd", matvar->dims[0]);
            for ( i = 1; i < matvar->rank; i++ ) {
                if ( ceil(log10((double)matvar->dims[i])) + 1 < 32 ) {
                    cnt += snprintf(size + cnt, sizeof(size) - cnt,
                        "x%zd", matvar->dims[i]);
                    if ( cnt >= sizeof(size) ) {
            printf("%-16s", size);
        } else {
            printf("                ");
        snprintf(size, sizeof(size), "%zd", Mat_VarGetSize(matvar));
        printf("%-16s", size);
        printf("%-16s0, mxclass[matvar->class_type - 1]);


    return EXIT_SUCCESS;

See Also

Mat_VarRead(3), Mat_VarReadInfo(3), Mat_VarReadNext(3)

Referenced By

Mat_Rewind(3), Mat_VarReadInfo(3), Mat_VarReadNext(3).

March 4, 2024