I am getting data from arduino and stored in database through ethienet. But when i got value ambientemp from arduino. it showed correct value when i tested on serial monitor. but when I use sprintf() I got -3275 or 0 value, which it is not correct value. Here is my partial code in sketch, please help...Here is guy doing his project. The result on Sketch serial montior is: ambientTemp 23.55 and then GET /getData/temp.php?t=-3278 I copied some of him: getting data and stored it into mysql
void getData() {
double ambientTemp=23.55; //to make it easy I assign ambientTemp a value.
unsigned long previousMillis = 0;
unsigned long currentMillis = 0;
long interval = 10000;
char strURL[70];
EthernetClient client;
// If there's a successful connection, send the HTTP POST request
currentMillis = millis();
if(currentMillis - previousMillis > interval) {
previousMillis = currentMillis;
if (client.connect(server, 80)) {
Serial.println("get data connecting...");
//client.println("GET /getData/temp.php?t=%d,temp HTTP/1.1");
// delay(10000);
Serial.println("ambientTemp");
Serial.println(ambientTemp);
sprintf(strURL,"GET /getData/temp.php?t=%d",ambientTemp);
delay(50000);
client.print(strURL);
client.println();
// client.print(strURL);
Serial.print(strURL);
}
else {
// If you couldn't make a connection:
Serial.println("Connection failed");
Serial.println("Disconnecting.");
client.stop();
}
}
}
You need to read up on C format specifications. "%d" means take the corresponsding variable (ambientTemp in your case) and interpret it as an integer. So what the runtime code is doing is looking at the bytes which make up your double, and interpreting the first 2 of those an in integer. Not what you want.... use "%f" as a format specifier...
Related
I placed "AAPL.csv" into the MetaTrader terminal folder's Files subfolder (MQL4/Files) to be accessible by the EA. The structure of this csv is as follows:
Date,Open,High,Low,Close,Adj Close,Volume
1980-12-12,0.1283479928970337,0.1289059966802597,0.1283479928970337,0.1283479928970337,0.10092189908027649,469033600
1980-12-15,0.12221000343561172,0.12221000343561172,0.12165199965238571,0.12165199965238571,0.09565676748752594,175884800
I want to read this, as well as many other similar csv files. All files have different lengths. My question is, what is the best practice when reading variable-length files? For now, I managed to read the content of my file by creating a 2-dimensional array:
string s[7][1000000];
although this is poor programming (what if the file only has 500 rows?) and it can still fail if I encounter a csv that is longer (what if file has 1000001 rows?). I tried using a dynamic array:
string s[7][];
but it returns '[' - invalid index value error. Yet another idea I had to use the FileSize() function and allocate just-the-necessary amount of memory to the 2-dimensional array. However,
int handle=FileOpen(FileName,FILE_CSV|FILE_READ,",");
if(handle>0)
{
int size = FileSize(handle);
...
yielded a size that equals the product of column numbers and row numbers. I was hoping to obtain a row_count and col_count and use them to define s:
string s[col_count][row_count];
My full working code:
extern string FileName = "AAPL.csv";
int init()
{
int row=0,col=0;
string s[7][1000000];
ResetLastError();
int handle=FileOpen(FileName,FILE_CSV|FILE_READ,",");
if(handle>0)
{
while(True)
{
string temp = FileReadString(handle);
if(FileIsEnding(handle)) break; //FileIsEnding = End of File
s[col][row]=temp;
if(FileIsLineEnding(handle)) //FileIsLineEnding = End of Line
{
col = 0; //reset col = 0 for the next row
row++; //next row
}
else
{
col++; //next col of the same row
}
}
FileClose(handle);
}
else
{
Comment("File "+FileName+" not found, the last error is ", GetLastError());
}
return(0);
}
int start()
{
return(0);
}
You should use the first dimension of the array for your rows and the second dimension for your columns. You would therefore have an array statement of string s[1][7];
You can then resize your array as you loop through reading your csv file as follows:
int handle=FileOpen(FileName,FILE_CSV|FILE_READ,",");
if(handle==INVALID_HANDLE) Print("Error opening file ",GetLastError());
else
{
int row=0;
while(!FileIsEnding(handle))
{
if(row>0) ArrayResize(s,row+1);
//carry out array reading here
//eg s[row][0]=FileReadString(handle);
//eg s[row][1]=FileReadString(handle);
//etc
row++;
}
FileClose(handle);
}
You can not resize the 2nd dimension of a multi dimensional array.
I'm getting a Internal Server Error with one of my scripts. I'm using MYSQL C API. https://dev.mysql.com/doc/refman/5.6/en/c-api.html
Here is the corresponding part of my script:
MYSQL *con;
MYSQL_RES *result;
MYSQL_ROW robe;
con = mysql_init(NULL);
if (!mysql_real_connect(valid values)) {
printf("Content-type: text/html\n\n");
printf("Could not connect\n");
exit(0); }
char somequery[512];
//userinput is sanitized beforehand
int sog = sprintf(somequery, "SELECT password from testtab WHERE username='%s'", userinput);
if (sog < 0) {
printf("Content-type: text/html\n\n");
printf("Something went wrong with Sprintf\n");
exit(0); }
int bos = mysql_real_query(con, somequery, strlen(somequery));
if (bos != 0) {
printf("Content-type: text/html\n\n");
printf("The query produced no result\n");
exit(0); }
result = mysql_store_result(con);
if (result == NULL) {
printf("Content-type: text/html\n\n");
printf("No Result Set Produced\n");
exit(0); }
robe = mysql_fetch_row(result);
char *passdb = robe[0];
printf("Content-type: text/html\n\n");
printf("And it is: %s", passdb);
A HTML form submits via POST to this script (part of which is seen above). When I submit a username which exists in the database beforehand, I'm receiving no error. Everything works fine.
The problem arises, when I'm submitting a username that doesn't exist in the said table(testtab). Well, I'm getting 500 Internal Server Error. I have looked at Apache Error log as well: "End of Script output before Headers".
I have tried a few things so far, but none of them worked. Any help is appreciated.
Note: Doing mysql_num_fields(result); in both cases gives 1.
First, you should NEVER store passwords in a database, especially one that is reachable through an online service. exit(0) indicates success. It's also short-circuiting your output before it is completed. You can't just call exit(0) in the middle of producing output. Use some kind of "data not available" string instead.
I have found the solution elsewhere, thanks to the help of some good people. It seems, that I had made a silly mistake as well as needed a thorough understanding of the difference between two MYSQL C API functions.
I'm writing the answer here, in hope of it benefiting others.
The mistakes is here:
robe = mysql_fetch_row(result);
Though it is correct in itself. I fail to check its result. What happens is that when the SQL query is performed using a username that did not exist in the DB beforehand, the result is a empty set (and not a error).
The mysql_store_result and mysql_fetch_row have a slight difference here. While the former will not return NULL if the set is empty, the later will.
All I have to do is add a check after the above line with the logic:
if (robe == NULL) {
//error occured
} else { //go on
}
I'm currently writing my own website and I'm trying to make sure that when someone is making an account the username is unique. I'm doing the back-end in C (since I don't know php/js) and I've been running in a bit of a problem. Right now I'm getting the environment variables in a file newuser.txt (this file has only unique usernames) as such:
fullname=test
description=test
username=test
password=test
I know that at lines 3, 7, 11 etc. in my newusers.txt file I will get my username so I thought of adding all the usernames to another file (which also hosts the incoming data) and then check to see if the incoming username is unique and if it is then I want to add all the data (so fullname, username etc) to newusers.txt. Here's my code:
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int main(int argc, char *argv[])
{
int currentLine = 1;
char fileLine[100];
int searchLine= 3;
char input[200];
int i=0;
int n = atoi(getenv("CONTENT_LENGTH"));
fgets(input,n+1,stdin); //get the input from the form
printf("Content-Type:text/html\n\n");
printf("<TITLE>Account Creation Query</TITLE>\n");
if (n == 0)
{
printf("<p> Error. Please try again.</p>");
}
FILE *f = fopen("newusers.txt", "ab");
FILE *g = fopen("incoming.txt", "ab");
if (f == NULL)
{
printf("<p> Error in opening the file. Check if the file exists</p>");
printf("<p>Login Page</p>");
printf("<p>Homepage</p>");
}
else
{
while(fgets(fileLine, 100, f)) /*searching for the usernames and adding them to the incoming.txt file */
{
if(searchLine == currentLine)
{
fputs(fileLine, g);
searchLine = searchLine + 4;
}
currentLine++;
}
char *token = strtok(input, "&"); /*tokenizing the incoming data and adding it to the incoming.txt file */
while(token!=NULL)
{
fputs(token, g);
fputs("\n", g);
token = strtok(NULL, "&");
}
}
printf("<p> Account created successfully. You can now login!</p>");
printf("<p>Login Page</p>");
fclose(f);
fclose(g);
return 0;
}
Ideally at this point my incoming.txt file would look like this:
firstname=bla
description=bla
username=bla
password=bla
username=u1
username=u2
username=u3
...
Right now I'm stuck at comparing the incoming username to the other usernames and then copying the data back into newusers.txt. Any help would be appreciated!
use system() call to invoke grep binary to search instead writing searching code in C.
as below
//concat strings to get "grep filename username | cut -d'=' -f2" into cmdstring and then
// read the contents
in=popen(cmdstring, "r");
if(in==NULL)
{
perror("Shell execution error");
exit(EXIT_FAILURE);
}
fgets(buf,3000,in)!=NULL)
here buf contains name of the new user then it is already exist.
otherwise he chose unique name.
I'd strongly recommend that you learn a scripting language for this project. PHP, Perl, Python, Ruby, Javascript… there's plenty of choices, and any one of them will be much more suitable for web programming than C.
That being said, what you need here is a database. Consider using SQLite or Berkeley DB; both are easy to interact with from C, and will allow you to perform lookups and insertions much more easily than would be possible with a flat file (as you're trying to do here).
The weird behavior is that a java.sql.Timestamp that I create using the System.currentTimeMillis() method, is stored in my MySQL database as 1970-01-01 01:00:00.
The two timestamps I am creating are to mark the beginning and end of a monitoring task I am trying to perform, what follows are excepts from the code where the behavior occurs
final long startTime = System.currentTimeMillis();
while(numberOfTimeStepsPassed < numTimeStep) {
/*
* Code in here
*/
}
final long endTime = System.currentTimeMillis();
return mysqlConnection.insertDataInformation(matrixOfRawData, name,Long.toString(startTime),
Long.toString(endTime), Integer.toString(numTimeStep),
Integer.toString(matrixOfRawData[0].length), owner,
type);
And here is the code used for inserting the time stamps and other data into the MySQL database
public String insertDataInformation(final double [][] matrix,
final String ... params) {
getConnection(lookUpName);
String id = "";
PreparedStatement dataInformationInsert = null;
try {
dataInformationInsert =
databaseConnection.prepareStatement(DATA_INFORMATION_PREPARED_STATEMENT);
id = DatabaseUtils.createUniqueId();
int stepsMonitored = Integer.parseInt(params[STEPS_MONITORED]);
int numberOfMarkets = Integer.parseInt(params[NUMBER_OF_MARKETS]);
dataInformationInsert.setNString(ID_INDEX, id);
dataInformationInsert.setNString(NAME_INDEX, params[0]);
dataInformationInsert.setTimestamp(START_INDEX, new Timestamp(Long.parseLong(params[START_INDEX])));
dataInformationInsert.setTimestamp(END_INDEX, new Timestamp(Long.parseLong(params[END_INDEX])));
dataInformationInsert.setInt(STEPS_INDEX, stepsMonitored);
dataInformationInsert.setInt(MARKETS_INDEX, numberOfMarkets);
dataInformationInsert.setNString(OWNER_INDEX, params[OWNER]);
dataInformationInsert.setNString(TYPE_INDEX, params[TYPE]);
dataInformationInsert.executeUpdate();
insertRawMatrix(matrix, id, Integer.toString(stepsMonitored), Integer.toString(numberOfMarkets));
} catch (SQLException sqple) {
// TODO Auto-generated catch block
sqple.printStackTrace();
System.out.println(sqple.getSQLState());
} finally {
close(dataInformationInsert);
dataInformationInsert = null;
close(databaseConnection);
}
return id;
}
The important lines of code are :
dataInformationInsert.setTimestamp(START_INDEX, new Timestamp(Long.parseLong(params[START_INDEX])));
dataInformationInsert.setTimestamp(END_INDEX, new Timestamp(Long.parseLong(params[END_INDEX])));
The JavaDocs on the TimeStamp ( http://docs.oracle.com/javase/1.5.0/docs/api/java/sql/Timestamp.html ) says that it takes in time in milliseconds since 1st January 1970 and a simple print test confirms this.
What I am looking for is:
A reason for this behavior when trying to store timestamps in a MySQL database through java.sql.Timestamp?
Any solutions to this behavior?
Any possible alternatives?
Any possible improvements?
EDIT:
Been asked to include what START_INDEX and END_INDEX are:
private static final int END_INDEX = 4;
private static final int START_INDEX = 3;
Apologises for not putting them in the original post.
Okay, look at your call:
insertDataInformation(matrixOfRawData, name, Long.toString(startTime),
Long.toString(endTime), Integer.toString(numTimeStep),
Integer.toString(matrixOfRawData[0].length), owner,
type);
So params will have values:
0: name
1: start time
2: end time
3: numTimeStep
4: matrixOfRowData[0].length
5: owner
6: type
Then you're doing:
dataInformationInsert.setTimestamp(START_INDEX,
new Timestamp(Long.parseLong(params[START_INDEX])));
... where START_INDEX is 3.
So you're using the value corresponding to numTimeStep as the value for the timestamp... I suspect you don't want to do that.
I would strongly advise you to create a simple object type (possibly a nested type in the same class) to let you pass these parameters in a strongly typed, simple to get right fashion. The string conversion and the access by index are both unwarranted, and can easily give rise to errors.
I am using the MySQL C API to query the database and I have the results stored in MYSQL_ROW types. I am able to print the results to the console with
printf("%s", row[0]);
however, according to the MySQL C API documentation, I cannot use them as null-terminated strings.
At the bottom of the function overview, they say I can "extract" the information with mysql_store_result() or mysql_use_result(). However, I am still confused as to how this is done.
Ideally, I want to use the results as a string so I can do stuff like strcmp, but otherwise I definitely need to use the information somehow with those two functions.
Can somebody show me an example of how to do this?
Basically, you call mysql_store_result() or mysql_use_result() to access the result set, the former loads all the rows into memory on the client side, the latter accesses rows one at a time from the server. If you use mysql_use_result(), you need to call mysql_fetch_row() to access each row until the function returns NULL. Each successful call to mysql_fetch_row() will return a MYSQL_ROW which you can use to access the individual field values.
Since the fields are not nul-terminated, you need to use mysql_fetch_lengths() to get the lengths of each of the fields so that you can copy them somewhere else via memcpy, etc.
Since the field values are not nul-terminated you will need to add your own NUL character when you make the copy if you want to use it as a string. Be aware that the field values may contain binary data, so if you do treat it as a string, functions that expect a C string will stop processing data if it encounters a nul-character in the data.
Here is an example from the documentation that should help you put all this together:
MYSQL_ROW row;
unsigned int num_fields;
unsigned int i;
num_fields = mysql_num_fields(result);
while ((row = mysql_fetch_row(result)))
{
unsigned long *lengths;
lengths = mysql_fetch_lengths(result);
for(i = 0; i < num_fields; i++)
{
printf("[%.*s] ", (int) lengths[i],
row[i] ? row[i] : "NULL");
}
printf("\n");
}