Im trying to debug a null dereference in my program. The program receives data from a web form submitted by the user. It seems that the problem is related with empty fields. When user submit the form the table data is finally retrieved in a char *tabledata variable.
tabledata handle the data of the table using this format:
"row1column1value/row1column2value/row1column3value|row2column1value/row2column2value/row2column3value|\0"
For debugging purpose im printing tabledata content using:
printf("\n tabledata is = %s \n\n", tabledata);
But when i submit the table if i leave the first column of the second row empty im getting this output:
tabledata is = 11/22/33/44/55/22/33|(null)/1/44/55/88/33/44|
How is it possible that printf does not stop printing when it reaches a null character? How can i check that this (null) value is really a \0 null character?
%s along with printf will not do it.
You have to use puts(tabledata);
Hope this answers your question.
Related
I'm new to elixir/ecto and I don't understand why my error_data field (defined as :binary in schema) gets inserted slash-escaped in my postgresql column:
params = %{error_data: "eyJtZXNzYWdlIjoiSW52YWxpZCB0b2tlbiIsImNhdXNlIjpbXSwiZXJyb3IiOiJub3RfZm91bmQiLCJzdGF0dXMiOjQwMX0="}
cast(%{}, params, [:error_data])
|> change(%{error_data: Base.decode64!(params.error_data)})
|> Ecto.Repo.insert()
Following #smathy insight, I've put an IO.puts(get_change(changeset, :error_data) between change and insert calls. It shows the data has beed decoded and is not slash escaped before insertion. But the next line showing Ecto query is escaped... Check my app's output:
[info] Creating error for 1 on channel 1
{"message":"Invalid token","cause":[],"error":"not_found","status":401}
[debug] QUERY OK db=0.5ms
INSERT INTO "errors" ("code","error","error_message","http_status","id","channel_id","inserted_at","updated_at") VALUES ($1,$2,$3,$4,$5,$6,$7,$8) RETURNING "id" ["error-03", "{\"message\":\"Invalid token\",\"cause\":[],\"error\":\"not_found\",\"status\":401}", "Invalid token", 401, 1, 1, ~N[2021-02-16 12:24:58], ~N[2021-02-16 12:24:58]]
Then check these DB queries out: the first is for the code inserted error. The last is from a manually inserted not-escaped error:
dev=# SELECT error FROM errors ORDER BY updated_at DESC limit 1;
error
---------------------------------------------------------------------------------------
"{\"message\":\"Invalid token\",\"cause\":[],\"error\":\"not_found\",\"status\":401}"
(1 row)
dev=# SELECT error FROM errors ORDER BY updated_at ASC limit 1;
error
---------------------
{"eita": "deu pau"}
(1 row)
How can I avoid that escape and insert the plain decoded ({"message":"Invalid token","cause":[],"error":"not_found","status":401}) content?
If I could use ecto fragments in insertion, I'd have told the DB to decode the base64 string... I didn't find how to do that either... any help?
I wonder it there is any environment configuration that affects ECTO in order to log it's queries and ends up string casting/escaping the error_data binary...
They're not really there, they're just being displayed by whatever tool you're using to print out that value because that tool uses "s as the string delimiter, and therefore escapes them to avoid ambiguity.
Same thing happens in an iex session, if you actually print out the value then it comes out as you're expecting because when you output a string it won't include the delimiters:
iex(6)> Base.decode64! "eyJtZXNzYWdlIjoiSW52YWxpZCB0b2tlbiIsImNhdXNlIjpbXSwiZXJyb3IiOiJub3RfZm91bmQiLCJzdGF0dXMiOjQwMX0="
"{\"message\":\"Invalid token\",\"cause\":[],\"error\":\"not_found\",\"status\":401}"
iex(7)> IO.puts v
{"message":"Invalid token","cause":[],"error":"not_found","status":401}
:ok
Update
This is me running a psql query after running precisely the code you've shown above on a string (varchar) field:
testdb=# select error_data from tt;
error_data
-------------------------------------------------------------------------
{"message":"Invalid token","cause":[],"error":"not_found","status":401}
(1 row)
Why moment().startOf('day') shows as Moment<2020-05-01T00:00:00+02:00>, in Nodejs ??
I want to show the date only, how to get the date only without Moment word and < > symbols.. !
So startOf() returns a moment object, what you're wanting to do is some kind of format of the output object.
console.log(moment()
.endOf('day')
.toISOString()) // 2020-05-18T21:59:59.999Z
Hi have a Spark dataset with one of its column having a Ctrl+M char present in the column's data, as a result that record is getting split into two records, and data corruption.
Even though I have added the code for handling regex newline \r\n, but I am not sure if this same code will be able to handle Ctrl+M, i.e. ^M:
filtered = filtered.selectExpr(convertListToSeq(colsList))
.withColumn(newCol, functions.when(filtered.col(column).notEqual("null"), functions.regexp_replace(filtered.col(column), "[\r\n]", " ")));
Will the code functions.regexp_replace(filtered.col(column), "<ascii for Ctrl+M>", " "); work ? ..I don't know the ascii value of Ctrl+M.
I have a text field in my SQLite database that stores a Time value, but for unrelated reasons I can't change the data type to TIME.
The values are stored in HH:MM format, and I'm having trouble trying to sort results by time because the values below '10:00' are missing a leading zero. I would prefer not to store the data with leading zero for the same unrelated reasons.
I'd like to add something to the Query that would pad the missing character if necessary, causing the results to read '08:30' when collected. I've been searching through the command and function lexicon though and I'm not finding what I need.
Is there a simple way to do this inside a query?
Thanks
I think this would work:
select your_col, case when length(your_col) < 5
then '0' || your_col else your_col end from your_table
Demo using Python
>>> conn.execute('''select c, case when length(c) < 5
then '0' || c else c end from t''').fetchall()
[(u'10:00', u'10:00'), (u'8:00', u'08:00')]
SELECT REPLACE(PRINTF('%5s', your_col), ' ', '0') FROM your_table
The PRINTF call pads the value with spaces until it's 5 characters, and the
REPLACE call replaces those spaces with zeros.
I am doing 2player game and when I get informations from server, it's in format "topic;arg1;arg2" so if I am sending positions it's "PlayerPos;x;y".
I then use split method with character ";".
But then... I even tried to write it on screen "PlayerPos" was written right, but it cannot be gained through if.
This is how I send info on server:
server.write("PlayerPos;"+player1.x+";"+player1.y);
And how I accept it on client:
String Get=client.readString();
String [] Getted = split(Get, ';');
fill(0);
text(Get,20,20);
text(Getted[0],20,40);
if(Getted[0]=="PlayerPos"){
text("HERE",20,100);
player1.x=parseInt(Getted[1]);
player1.x=parseInt(Getted[2]);
}
It writes me "PlayerPos;200;200" on screen, even "PlayerPos" under it. But it never writes "HERE" and it never makes it into the if.
Where is my mistake?
Don't use == when comparing String values. Use the equals() function instead:
if(Getted[0].equals("PlayerPos")){
From the Processing reference:
To compare the contents of two Strings, use the equals() method, as in if (a.equals(b)), instead of if (a == b). A String is an Object, so comparing them with the == operator only compares whether both Strings are stored in the same memory location. Using the equals() method will ensure that the actual contents are compared. (The troubleshooting reference has a longer explanation.)