Read A Specific Line From A File | C++ Example

[@natsue-bw1zu]

Ive spent 6+ hours and all it took as a 6 min video to solve this. Thanks for the amazing video

[@PortfolioCourses]

You’re very welcome! :-) I’m glad to hear the video helped you out!

[@Nixhekoo]

same here!

[@Nixhekoo]

I've been searching for fstream tutorial everywhere but its so difficult to understand everywhere. You made it easy to understand! Props to you!

[@PortfolioCourses]

I’m so glad it was helpful for you, and thank you for leaving this positive feedback too! :-)

[@ct6502c]

This worked perfectly! The way you explained everything in a step by step way was a huge help. One other thing I really need help with though is how to search a text file for a string? I have looked everywhere and tried using Getline() and the search function in a loop, similar to what you did here...but I can't get it to work. All I would need it to do is tell which line in a text file the string was found.

[@PortfolioCourses]

I'm glad to hear it was helpful! 🙂 And that is a good question. I don't have a video on that yet, but I'm going to add it to my list of video ideas. You could check whether a string is in a text file at all by reading the entire contents of the file into a string: kzbin.info/www/bejne/p2qadmuohKuKibc. And then something like .find() should be able to help you find the string if it is there: cplusplus.com/reference/string/string/find/. But if you want to find the line number that will be a bit trickier. You could maybe use this approach here: kzbin.info/www/bejne/gWizmmOgfNOsp9k. And as you read each line, you could use .find() to try to find the string, and the counter variable that is being used for the array in that example could help you to know the line number if you find a match (you probably need to add 1 to it).

[@ct6502c]

@@PortfolioCourses I got it! It turns out that it WAS working, there was just an unrelated problem with how I was using a variable. But yes, combining the method you explain here using a loop and keeping track of the line number, and using the find() function will search for a string AND tell you which line number it's on :)

[@kirikor7]

Nice video, would be nicer if you kept the code a bit more zoomed out to get the big picture. Especially towards the end. Cheers

[@PortfolioCourses]

You can see the full code example here: github.com/portfoliocourses/cplusplus-example-code/blob/main/read_specific_line.cpp. Other people tell me I should zoom in more because they like to watch the videos on their phones, so it's always hard to tell what is best for people. 🙂

[@comic-typ5919]

@@PortfolioCourses personally, I like it zoomed in :D

[@moodymonstrosity1423]

The file.eof() function does not work correctly for reading objects from a file as it copies one extra object. Does it not do the same for reading text data?

[@PortfolioCourses]

Great question! :-) The eof function really just tells us if we’ve reached the end of the file or not. Whether the program reads “extra” information or not is determined by how the program is written, not by the eof function. So in this example, we are not reading any “extra” text data.

[@framo_official]

my test.txt just wont open.. i alos tried giving the whole path, did not work :(

[@larenshboro3659]

So the while loop reads the next line automatically if the current line is not same as line number and the end of file is not reached?

[@PortfolioCourses]

Yes that's correct Larensh. :-)

[@varadarajkamath404]

How do I take a string (which is a substring of the file) as my user input which I want to search in the file and print out only the line containing that substring. Example: In my menu.txt file there is a line "Pizza cost: $4" In my program file I take a user input as "Pizza" and I want the entire line "Pizza cost: $4" to be displayed and not the other lines.

[@PortfolioCourses]

This is a great question Varadaraj, but I would almost need to make another video to answer this question. :-) You would need to read each line of the file somehow, maybe somewhat like in this video: kzbin.info/www/bejne/jpLNfHyEiNB_f6s. You don't necessarily need to store each line into a vector like in that video though. What you could do instead is use the find() function to look at each line/string, and try to find the string you are looking for in that line/string: stackoverflow.com/a/2340309. You could also store the lines into a vector or some other data structure, and then loop through the data structure elements afterwards and try to find the line/string containing the string you are looking for using the find() function. Good luck! :-)

[@leythecg]

premium content as always! Many thanks!

[@ManOwaRR1]

Hello Sir, i've been looking everywhere for an algorithm , to find a specific word in a string on lines , example "hello world, welcome to c++, tutorial" , i want to search the file , let's say to find , "c++" , i wrote a search function , to look inside array or vector , result same it's only finding , the first element "hello" and disregarding the other elements, any tutorial about that would be appreciate it , big thank you .

[@PortfolioCourses]

So just so I'm understanding correctly... the program would read each line of the file and store it into a vector of strings. Then it would only keep those lines/strings in the vector which contain a string, like "C++"?

[@ManOwaRR1]

@@PortfolioCourses Thanks for the reply , i worked around it yesterday , using for ranged loop , but to give u an overview of what was actually happening , i have filled with strings read from a file , was trying to iterate through it using std::vector ::iterator it , when i was iterating using it = std::find(vector.begin(),vector.,end(), match), it was only matching the first string element inside the vector , example "hello world", it matches the hello but never matches the "world" , not really sure why it's matching the first element , while it''s not matching the second element, hope that's clear , i can show the code , if needed , still would love a video about searching/replacing/deleting elements inside vectors , thank you

[@PortfolioCourses]

@@ManOwaRR1 I'm glad you figured it out, and thanks for the video ideas. 🙂

[@pawemarkowski5387]

I need support. Location of the text file is: e:\tekst.txt . Program ask for the name of the file I want to read. Name of the file is written into string filename. Unfortunately I receive information " file failed to open ". How to give a path to the location of the file tekst.txt in the program line line -> plik.open(filename); ?

[@PortfolioCourses]

Good question Pawel! :-) Maybe try this? plik.open("e:\\tekst.txt"); I think you might need to give the 'absolute path' of the file that includes e:\. But \ is a special character called the 'escape character' in C++ strings, we use it to output characters like the newline character with . To actually represent a \ character in a string we need to use \\.

[@hariprasad-q6u]

Which editor ur using g

[@PortfolioCourses]

Visual Studio Code :-)

[@zainuldin9095]

you could do while ( getline (file, line, ' ') ) { }

[@PortfolioCourses]

Thank you for sharing this approach! 🙂

[@tioa.p.1058]

what does that syntax mean bro???

[@tioa.p.1058]

i dont understand

[@zainuldin9095]

@@tioa.p.1058 checkout getline docs at cpp reference

[@zainuldin9095]

@@tioa.p.1058 from cpp reference docs Parameters: input - the stream to get data from str - the string to put the data into delim - the delimiter character Return value: input

[@i_m_wali]

You made it So freeking ez!!!

[@elinesiobrito3333]

Good 🤠

[@ShadyOk]

life saver