Trouble writing to file

[Christianvs]

Hi

I got a problem with saving some data to a file on my system.

As the picture shows i got a vector of float in which i store some data. This vector is then stored in another vector which is declared in my header file:

I do a n++ to keep track of the number of vectors that is stored in the vector rtlData.

When i press a button called saveRTLData i write the vector rtlData to a txt or preferably a csv file. And here is where my program crashes.

To begin with i wrote the whole path "/home/user/.../rtlData.csv" in my code and when i pressed the button i got the message "Stream not open". Then i tried changing the path so it's just rtlData.csv or rtlData.txt as the picture shows, which resultet in the following error:

[rtl_temp_node-3] process has died [pid 15572, exit code -11, cmd /home/christian/catkin_ws/devel/lib/rtl_temp/rtl_temp_node __name:=rtl_temp_node __log:=/home/christian/.ros/log/4c8dc630-2133-11e8-b647-b8ee65ea785f/rtl_temp_node-3.log].
log file: /home/christian/.ros/log/4c8dc630-2133-11e8-b647-b8ee65ea785f/rtl_temp_node-3*.log

Does anyone here know where my mistake is?

[JonB]

@Christianvs
It helps if you paste actual textual code, not screenshots...

for (int i = 0; i <= n; i++)

If n is the number of rows ("vectors"), don't you mean i < n, as is standard in all C-type languages?

[Christianvs]

@JonB
I will remember that!

It seems to have been the problem, what a stupid mistake! :)

But thanks for the answer!

[JonB]

@Christianvs
Yes, get used to the fact that in C-type an array with n elements is always index from 0 to n - 1, inclusive. Trying to access the n-th element will crash (if you're lucky) or exhibit completely unknown behaviour (if you're unlucky).

[VRonin]

since rtlData is a std::vector there's no need to keep track of n. just use rtlData.size()

[mranger90]

Or, since you're using a container, use the appropriate iterators.

[VRonin]

@mranger90 said in Trouble writing to file:

Or, since you're using a container, use the appropriate iterators.

Which would mean:

for(const auto& singleRow : rtlData){
for(const auto& singleVal : singleRow){
rtlDataStream << singleVal; 
}
rtlDataStream << std::endl;
}

[Christianvs]

Thanks for all the replies folks!

I feel quite stupid for not seeing that .size() actually solves the entire problem, but I am still quite green when it comes to programming.

Thanks for the tip with iterators @mranger90 @VRonin ! I'll look into that