function n = pnm_getint( file )
#
# PNM_GETINT(file) - read an integer from a pnm file
#
#    file : file id for open file
#

    # read past white space
    while ( 1 )
        ch = pnm_getc( file );
        if ( index( " \t\n\r", ch ) == 0 )
            break;
        endif
    endwhile

    if ( ~isdigit(ch) )
        error( "pnm file format error" );
    endif

    i = 0;
    while ( 1 )
        i = i * 10 + str2num(ch);
        ch = pnm_getc( file );
        if ( ~isdigit(ch) )
            break;
        endif
    endwhile

    n = i;

endfunction