C++ Tutorial - 24 - Reading From a File

[@cmommsen1]

@rockydasha Re:Basically, bucky is a variable of type ifstream, due to this statement: ifstream bucky; And after this statement: bucky.open(filename); bucky is now "connected" to the user-defined file name contained in filename - in this tutorial, "beefy.txt". Therefore, when you use it with >> (known as the extraction operator), the stream looks in beefy.txt, finds the letters 't', 'h', 'i', and 's', and "streams" them into word. The next letter is a space, so the stream operator terminates.

[@InSpmindss]

you are the best teacher i ever have seen in my life, in real sense ,you teach in the best way , a lot lot more thanks to you for providing such materials

[@CensSka]

I've got an exam tommorow I'm screwed

[@thinumstoneheart6713]

LMAO same af man

[@informativecontent4778]

mine is tommorrow wish me luck

[@jimmychan9282]

mine is tomorrow

[@ZainiverseCreations]

Mine is tomorrow LOL .. Everyone comes to bucky a day before exam ...

[@Mustafalllica]

mine is tomorrow

[@zarigull274]

This link is best to learn programming because before this i had no idea about file handling but know i can describe this frequently thanks

[@colinrickels201]

i have gone to hell and back looking for a tutorial such as this thank you so much

[@Haris0423lhr]

you look like jesus so no problem for you

[@johnnyc130]

Great tutorials. You are very clear in all of them and dont leave me confused like some other tutorials. I made a program that can open files, and create files to write on.

[@Finalfox09]

Thank you this tutorial was a life savior

[@jgray110]

Thanks Bucky, finally got a file to read after dozens of other search code attempts because I was afraid I couldn't do this, but I tried it and walla, don't forget to bucky.close after while { }. system{"pause") is operating system dependent so eventually we need to learn OS independent code. These tutorials get an A++

[@rybread5718]

Thank you my good man. I used #include and it worked the same.

[@christophergaspar6520]

anybody who sees this please help, i wrote a code similar to this in my visual studio I then noticed that, when the program is displaying the text file, the last word is not included. even in bucky's program, notice at 6:05 the last word ('C++') is not included. is there a way to fix this I would greatly appreciate your help, thank you

[@Qazqi]

Not sure why you'd prefer character arrays over std::string. Anyway, just read it with while (std::cin >> word) {std::cout

[@concernedviewer6909]

Just wanna say again, Welcome back Buckey!!!

[@OnlineMediaCollection]

Just needed this line, *while (iMyFile.good())* LOL. Thanks!

[@thetruereality2]

That wouldn't print anything, it would only work in case of an eof function. I think you meant while(MyFile.good)

[@naimcool36]

@@thetruereality2 hes right "good" is a function

[@RazRikimaru122]

Hey is there any possible way to make the number from each line in the text file output into an array grid of variables ?

[@usabnd]

@linglihe ofstream is for output file. it means if you want to change the content of a file.. hope I helped

[@yomguioim]

you can get an open file box with tiny file dialogs on sourceforge is a single C C++ cross-platform file offering many native dialogs.

[@Boeing737Channel]

@Yikak4 cin.getline = just like cin >>, just can manipulate it more. It gets the line you enter. (filename,50) is to store what you inputed in filename, and you need to include 50, the char character size.

[@keykeyine]

Just as a side note, the way you set this up it's never going to print off the last word in the text file you read in. Not a big deal but I thought it might confuse some people. You just need another cout

[@FastCodeDeveloper]

man you must be the most subscribed programmer-youtuber of all time...

[@reggaemediatv]

Thank you

[@octav3k]

@Duodecillian 50 is the maximum number of characters that variable can hold. So if you had a filename or word (the variables he defined inside the program) that's longer then 50 characters, only the first 50 would be read by the program.

[@MozartTime]

I just needed to refresh my mind about fstream. Loved this , so clear as good.

[@Wingedzephir]

Great you just solved all my problems with this simple example...well done thanks!

[@Jonko192]

good for beginners. only a few tips to improve this program: change system("pause"); to cin.get(); and why using cstdlib? the stuff is already in the iostream library. the best thing to do is put the load stuff into a function and inside the function you put a return statement if the file is not open. dont use exit(exit_failure);

[@PaxiKaksi]

But getline eats the last word in your text so........ That is a bit inefficient ?

[@h8errage]

@shebotnov ofstream enters stuff into a file, and ifstream gets stuff from a file(read a file) i think u can use an fstream object that does both so u never have to ask yourself that question.

[@bwneyeschik]

Do you do this often? If you do I may continue with programming. Otherwise, I think I may change my Major!! (this online class thing sucks!)

[@sum21chan]

I like ur video!! just wanna remind you, you could press the tab button for go in 5 space (I think) instead of pressing the space 5 times!

[@arraybabe8514]

yes, use getline and dont forget to include the string header

[@helpfullprogrammer]

how do you output the whole con-tense of the file? I can only get one word. thanks in advanced! from helpfullprogrammer.

[@Digiscat]

If you ARE confused, just think a bit and mess around with the code. It'll help you both understand and remember. If you're like me, cin.getline and the array threw you off. cin.getline is like a more flexible cin >>---- So, in other words, its like he put "cin >> filename[50]"....get it? And if you make the number for the array smaller, that just limit how many characters it can hold. So, -- char file[50] -- can hold up to 51...but if you put file[1], itll only USE 2. (+1 since 0 counts.)

[@r3sp3c791]

Couldn't get a think from this one, it was so fast!!!

[@muhammadbinsaleem8565]

Bro ! May you live happy life...

[@razeal113]

its saying that the char string can be up to 50 characters long. ie, he doesn't know the length of the filename ahead of time so he allows for up size 50. if he was worried about extensions (blah/blah2/.../file) might have made it larger, but 50 should do for any file

[@Mrlpjo]

@TheResponsae. Is that really needed??? I think the file automatically closes once the execution is over?!

[@GNSstudios]

you showed how to write a file but what if i wanted to write the file to a specific directory.

[@josephrowell9052]

When I do this, whatever actual file there is, it prints loads of zeros?

[@Mowteng]

i dont understand how you can go through each loop, where in the code you told C++ that you want the file content separated by space? why is the first cout in the while not the complete content of the file (with a max of 10 chars ofc) ?!?

[@yasirwisal8081]

Hi Bucky, How do you end line if there is a large text file with the string data type and do some calculation from data which is in text file?

[@reggaemediatv]

what part of it dont work?

[@octav3k]

@Silvertide82 You can create a file with Notepad (he did so before running the tutorial) inside the directory where he saved his cpp file. For example, if he had "tutorial.cpp" inside "C:\Users\Greg\C Toturials\", the text file would have to be in the same directory: "C:\Users\Greg\C Tutorials\beefy.txt". I hope that clears it up for you.

[@mynewlife210]

Where should the file be located??

[@HarisMalik]

instead of adding cstdlib we can use same code but exit(0) and the program must exit

[@insomeperson]

Why does it always ignore the last word?

[@octav3k]

Tou can't see the last word because the condition on the while function is put before the body of the function (he used while, not do-while) and each time the program reads a word with "bucky >> word", it moves to the end of that word. After it reads the last word, the function "bucky.good()" becomes false and it doesn't enter the loop again in order to post the variable (word) to the screen. He could have avoided this either by using do-while or through the method described by andreipopescu87.

[@TheHeadmanmr]

What is this used for?? Would be much easier for my brain if I knew how this would be used in a real situation... !

[@euktalinoo]

i want to read an array and i want to covent a string in to an integer.can you help me please?

[@genjimidou]

After seeing 5 times I finally understand ...xD

[@Lightscribe225]

Say I wanted to take a list of random numbers from a file, and find their sum and average. How do I go about doing that? Do you have a tutorial going over that somewhere?

[@chuserio2]

hey can u explain, why the 50 on the char file name? what it represents

[@stereojos86]

you save the txt doc in the same folder that the program? My program dont read the txt, go directly to exit(EXIT_FAILURE); I copy and paste your program.

[@dumacele6724]

so relatable "come on baby",,,exctly how we al talk to our computers when we're in the zone

[@LPSlasher]

3:30, People: keep in mind that using SPACEBAR in an empty line may wreck the code sometimes, don't try it. (in empty lines you should use either TAB or ENTER... Of course you CAN use SPACEBAR after a codeline)

[@adeepnair]

how do i do this with a text file with numbers in it?

[@TheSheniceJ]

+Adeep Nair ik its like a year u posted this but same thing i wanna know :(

[@TheHeba66]

how can I create a file in the same directory? where exactly should I save it?

[@Humbertorgr]

Ok it worked for me... But I made a txt file with two lines and is only showing up one :s... is there a way to use it with string instead of char?

[@m4unot]

Can you open a "makefile" and use command: "make flash" to run it?

[@baarbie0786]

So what is the ideal way of reading from a file?

[@WikiPeoples]

how come it didnt read the entire line? It left out "C++!" .... mines doing the same thing

[@SimpleCookiee]

I wonder one thing tho... Let's say I recieve a input as value into a char[50].. Assume it got the value "people".. Now here's my question.. How do I add text to that variable? I want to add ".txt" at the end so I becomes "people.txt", how to do that?

[@chernobila]

hello sir are you going to post more C++ tutorials? Please do Thank you

[@anikatahir6146]

Im having this problem that i have to construct a program to read my file where i have to provide choice for the user to select. Like i saved names and roll numbers in my file and now i have to provide option to user to select which roll number's name should be displayed/read....

[@shekhardk]

Well this code doesn't read and print the last word in the file. If the file has just one word then it won't print anything.

[@ivaka92]

20 y.o. here :) it was an honest reaction really - stuff until here was easy to comprehend and suddenly lots of commands and info! When i watched it 2-3 more times i got the hang of it... almost :)

[@shidono6786]

are you working now?

[@IvanRubinson]

how do i made it so i decide wich file to open (as a programmer)... I mean pre-define that filename = [something]

[@tarBall313]

Why don't you use Visual Studio?:)

[@meyerflyer34]

It could be used for storing options in video games and then outputing them with a custom GUI.

[@sarahbiebah]

Why doesn't line 6 CREATE the file like we have done before? How come this time it needs the file already created? What's different?

[@MrBrightSide622]

ugh. Do you need to be admin like the last one?

[@DRDSkidroW]

@SuperiorOnRoblox make sure you placed the exclamation mark in: " if (!test.is_open()){ " that was my problem

[@Yizak]

What is cin.getline(filename, 50) ?

[@muhammadmohaiminulislam7189]

Can i write or read a character in a file at a selected position?Like adding 'a' at 2nd line , third position at file? Or read from a selected position?

[@blacksven1]

What is the [50] for???

[@doerparol]

How can I make the program to store single characters instead of words? Afterwards I would like to process that stored information and count each letter so number of a= 50 b = 46 and so on

[@davidalyakobi6857]

Hey Bucky why did you use exit(EXIT_FAILURE) instead of exit(1) ?

[@m4unot]

why do you say: char filename[50]; why 50 ? do you limit char with?? so if i say 5 .. i can only type 5 char??

[@SuperFireEagle]

how would you code it to where it can automatically detect the input file name without hardcoding the name of the file into the program?

[@yoloop93]

mine doesn't open as text file but opens with cmd.help!

[@muhammadfariezdaniel4769]

wah thankyouuu>< I am watching this in 2021

[@chaouchsamir3635]

what do you mean by using [ 50 ] ?

[@dkblade27]

I thought when we open a file that we don't have, C++ will create it for us. So how come tunafeesh.txt didn't open??

[@TheMohawkNinja]

@linglihe I think that of is Output File, and if is Input File

[@zeen5163]

does "bucky >> word" get the word from the user and stores it in the file? or what does that actually do?

[@durraiz_ahmad18]

Can you tell how can I skip/ignore line or row while reading a csv file and storing it in a 2d array?

[@oumie93]

Please help: do you know how can I input a ply file via C++ language ....?????

[@TheAl2kas]

Hey, thanks for a useful tutorial, but I have a little problem. Program won't print last word. How do I fix it? :l

[@Pcatalin66]

+Aldis Petrauskas That is because the text is in that "char word[50]" and word[50] have only 50 slots. If you enter an text longer that 50 caracters (space included) than your program will cut the rest and stop at the 50 caracter. :D make sure that you give more than [50] ... maybe word[100] will help you .

[@RexGalilae]

+Aldis Petrauskas The reason is because he types *bucky>>word* before *cout

[@RexGalilae]

Lily Rathbun You first open the file and give it an alias (i.e. a placeholder) name, in this case, bucky. If you opened the file as , say "Lily", then you simply swap out all the "bucky"s from the code with "Lily"s. Pls. tell me if I misunderstood your question. I think I have misunderstood it.

[@RexGalilae]

Lily Rathbun If you're talking about the location of the file in the directory, then it's automatically created in the same folder as your program.

[@15sunny1]

+Mohammed Zaid Thank you!

[@AndToeKnee1]

what if you want to copy codes from a website and paste it back like the ones to prove your not a computer ? lol

[@pranoydutta5435]

instead of including the cstdlib to use exit, can we just return 124721; as this is in main

[@Milo_1105]

Is "People" a class?

[@leoking938]

Why is filename a char insted of a string?

[@moazelsawaf2000]

F

[@nilufargh]

why did you use "of stream" in the other video for writing a file ?

[@randohinn6691]

o -output i -input

[@nilufargh]

***** Thanks, if you don't mind, I just have a question about reading a data from a file and store it in a matrix. We have some data in a file that shows the amount of precipitation in specific time (like month and day). So our Prof built a matrix by getting the # rows and columns from the file. Then He set all the elements in that matrix= 0???!!!! ( In vectors and matrices isn't it like not having a value means zero so why do we have to set zero again?!) . Anyways and then in order to put those numbers into the matrix he said m.at(rows-1).at(columns-1)= num, we read the num from the file with rows and columns but why rows-1 and columns-1????

[@randohinn6691]

matrixes and vectors are 0 indexed so, the first element actually is at position 0 in the vector and so forth

[@nilufargh]

***** True, but when you resize a matrix. let's say typedef vector< vector< int> > matrix; matrix m; m.resize(rows); for ( int i= 0; i< m.size(); i++) { m.at(i).resize(column); }// So now we built out matrix which is empty that means now all the elements are zero, right? we don't have to set all the values=0 again, it's not like arrays that elements are Not Defined unless we put a value in it. Right?

[@leezhijiang]

What if that is an integer value ?

[@hexmedi]

@HamishWare when you don't specify the directory, it searches for the given file inside of your project folder. at least this is how it works for me

[@Mrlpjo]

i understood after watching the third time... not so confusing as i thought at first..

[@abdulz1]

hm... my file do not open ???

[@fernandinhoflor]

Add in the end of while the following expression: if(!bucky.good()) { bucky >> word; cout

[@Johnlolmann]

why do it open the file in cmd and not in notepad

[@JosePimenta_JP]

hi, how do i read a code from a file? like instead of just opening a file and read the text. i want to open the file and read code that is inside that file. how it is done? thanks in advance

[@josephchotard]

I know it's been a year but it would actually be impossible unless you implemented a compiler into your script to compile the code as C++ must be precompiled. If you really want to do this you should use Python

[@kurekvision]

why do you make some programs in console by using c++ (very hard way) if you can do the same stuff with just few lines in notepad (batch file) and its very easy. I dont get you guys.

[@Niffisa]

There is a problem with this program. It wont output the last word in your .txt file ;-)