C file read to end. string contents = reader.

C file read to end rb+: Open for both reading and writing in binary Nov 23, 2014 · I am trying to read a file and return it as a UTF-8 std:string:String it seems like content is a Result<collections::string::String, collections::vec::Vec<u8>>; if i understand an error Imports System. And I want to count how many numbers are there. Please Help me! Here is the code, while ( !feof ( in ) ) Sep 13, 2014 · I need to create the Qt5/C++ equivalent of 'tail -5 myfile' (without using a shell command. When a synchronous read operation gets to the end of a file, ReadFile returns TRUE and sets the variable pointed to by the lpNumberOfBytesRead parameter to zero. After searching here, I figured that fread / fwrite should work unsigned char buff; fopen_s(&input, "input_file_of_any_kind", "r"); fopen_s(&output, "new", "w"); while (!feof(input)) { fread(&buff, 1, 1, input Now, suppose you want to read the file again (from the beginning): in. binary form. fseek takes a third parameter that tells what the position is relative to. eof while loop. I probably need to implement some kind of end of file operation, but I'm not sure how to do this with the istream overload and iterator. Jun 21, 2016 · Yes - you would probably be arrested for your terriable abuse of strcat ! Take a look at getline() it reads the data a line at a time but importantly it can limit the number of characters you read, so you don't overflow the buffer. Since std::stringstream or std::ofstream are derived classes you can pass both of them equally into this function. It cant find the EOF special character at the end of file (arq1) that would tell it to finish processing. . The length of the string is known ( Length property), so it's not necessary When reading a file, you can check : Apr 26, 2015 · C Read until end of file. Then when you need to know if there is more to read in the file, you simple check the current file position and compare it to the one at the end. I think my best bet is to use while type cycle with a condition to end counting then another line starts but I do not know how to stop reading at the end of a line. Oct 19, 2012 · Supposedly he stored that byte position the previous time he read the file, and now he just wants to read the part that's new. C language provides different functions such as fopen(), fwrite(), fread(), fseek(), fprintf(), etc. Yep, the C standard says supporting that is optional. If the file does not exist, fopen() returns NULL. Use fread to do block reading of the file. The third parameter requires a file pointer that is used to read the file (fptr in our example). How to know it's the end of the line in c++ reading file. Nov 27, 2010 · C - reading past end of file with fgetc. the read() system call will return 0. If a file is open, and have read to the end of current file size. dat": one two three The following code will print all text after the first four bytes using an mmap() based approach: Jan 25, 2018 · Try to open the file with "a" mode, example: file=fopen("FileName. May 7, 2013 · To find a position in a file, use fseek(). But one way you can check for end of file is by testing the function return value from fscanf Input/output with files C++ provides the following classes to perform output and input of characters to/from files: ofstream: Stream class to write on files; ifstream: Stream class to read from files; fstream: Stream class to both read and write from/to files. This sort of fread() usage was briefly touched upon in the excellent book C Programming: A Modern Approach by K. I used a fscanf to read each line of the file, and another one to check for end of file. Feb 2, 2024 · Use fopen and getline Functions to Read Text File in C. There is no knowledge in C/C++ file handling to know about where lines start and/or end, other than in the sense that there are "end of line markers", newline ('\n'). Something like this: Jun 16, 2019 · In addition, while(!feof(file)) is (almost) always wrong, because the flag is set after an unsuccessfull read has reached the end of the file. N. Jan 31, 2024 · In C++, EOF stands for End Of File, and reading till EOF (end of file) means reading input until it reaches the end i. Just read character by character and do not worry about the exceptions because the condition in the while loop is handling the exceptions :D May 24, 2013 · Use read system call. This while loop would be nested in an !infile. docx File size is : 12920 bytes (according to SEEK_END) File size is : 12920 bytes (according to freed) PK when I changed the code to this Sep 15, 2017 · Generally C doesn't care what the contents of a file are. / for different line. See full list on geeksforgeeks. Exists(path) Then File. Dec 31, 2018 · I understand from C manpage that using fgets(), reading stops after an EOF or a newline. The results show the time (in ms) that each piece of code took to read the files. so you still can't use it to distinguish error and end of file in that case, feof is needed. a letter or a punctuation character). fread() is often used to read fixed-length data records directly into structs, but you can use it to read any file. txt", ios::binary ); is. Lines without whitespace characters Jan 7, 2021 · In this article. In this article, we will learn various methods through which we can read inputs until EOF in C. Zero termination is only required if you later interpret that data as a C-style string. In this article, we will discuss how to read the input till the EOF in C++. In C: Reading integers from a file. Oct 11, 2024 · The fread() function can be used to read data from a binary file in C. 2. This is the output I got . Of course, you need to be sure that the file doesn't get overwritten in the meantime (a log being cycled for example). feof() works by returning whether the last read operation on a file read the EOF mark or actual data (well, you are using fgetc() but the behaviour is the same anyway) Jun 17, 2024 · In C, reading a file line by line is a process that involves opening the file, reading its contents line by line until the end of the file is reached, processing each line as needed, and then closing the file. If the conversion was using a numeric type (e. seekg (0, ios::beg); Feb 28, 2017 · the "w+" mode, clear the previous content of the file and the file will be empty when you just going to read the file without writing anything to it. Jan 13, 2017 · I can only use malloc, and read to handle this, open is only for testing, and I don't understand why it does this, usually read returns the number of bytes read in that file, and 0 if it reaches the end of file, so it's a bit weird to see this. Nov 16, 2021 · I'm trying to use the code below on the ifstream twice - before I read anything from the file, and after I read to the end of it (using readline()). Thanks for your help in advance ;) Aug 9, 2012 · While I can certainly imagine cases where a file terminated with an 'end line' should return the empty string, I think ignoring the last 'end line' character would be more appropriate when dealing with regular text files; if the file is terminated by an 'end line' character we properly ignore it, and if the file is not terminated by an 'end Mar 5, 2021 · For starters I want to be able to read and write the same file, but I'm having trouble doing that for any file other than text files. Let's consider some common mistakes done by beginner C++ programmers, and a proper way to read the file. If getc returned a char, there would be no way to indicate the end of file without using one of the values that could possibly be in the file. 3. Right now the txt file has 10 "orders", but it only reads the first one into the orders vector. If the file does not exist, it will be created. IO; class Program { static void Main() { using (StreamReader reader = new StreamReader(@"C:\programs\file. If you use fgetc(), it will return EOF, a negative int value that's distinct from any unsigned char value. txt has abcdefg\0, once it reaches \0, close Oct 30, 2013 · The final newline at the very end of the file does not start a newline, it merely marks the end of the current line. If execution is allowed to continue, the function returns -1. But my original statement holds. EOF indicates "end of file". King. Mar 29, 2017 · What i read from a file: a P1/ s/ e/ t etc. I ran the test: checking the file size, malloc a buffer, read the entire file into the buffer, close the file, free the buffer. If you capture the return value from fgets you'll know when you're at the end of the file, and using the above code you'll know if that last line ended with '\n' or not. Meaning it has not read anything at all. A newline (which is what happens when you press enter) isn't the end of a file, it's the end of a line, so a newline doesn't terminate this loop. Alternatively, we can skip retrieving the file size with the stat function and instead iterate over each line of the file until the end is reached using the getline function. If you want it closed immediately, call close; otherwise, just let the stream go out of scope and the destructor will take care of it for you. Testing it before a read is therefore nuts. 1. Aug 18, 2015 · If your task is not to invent the line-by-line reading function, but just to read the file line-by-line, you may use a typical code snippet involving the getline() function (see the manual page here): May 13, 2013 · When opening the file you can seek to the end of the file, get the file position, and then seek back to the beginning of the file again. If the End-of-File is encountered and no characters have been read, fgets returns NULL. The ReadFile function checks for the end-of-file condition (EOF) differently for synchronous and asynchronous read operations. When I print the the results from the file i get this: johnny smith (Home)3 (Cell)4 x☺&gt; x☺&gt; (H file looks like this: abcd efgh ijkl I want to read the file using C so that it read the last line first: ijkl efgh abcd I cannot seem to find a solution that does not use an Don't use while(!file. Feb 12, 2010 · ifstream has peek() function, which reads the next character from the input stream without extracting it, simply returns the next character in the input string. Therefore, you could append the read characters directly to the char The first parameter specifies where to store the file content, which will be in the myString array we just created. (A text file that doesn't end with a newline character might not even be valid, depending on the system. txt in c. in. you can not use strcpy(&tempToken[i], &tempChar); to copy char. 10. When implementing the io::Read trait, it is recommended to allocate memory using Vec::try_reserve. However, this behavior is not guaranteed by all implementations, and read_to_end may not handle out-of-memory situations gracefully. read(buf, 100); // Try to read again. That's necessary because C has no way to tell the length of an array. I looked at a c++ function like fgets but file is being read in reverse. My problem is, the code does all the job it is supposed to do but it doesnt end. ¯_(ツ)_/¯ any ideas why? #include <iostream> #include <;fstream&gt; using namespace std Feb 1, 2015 · I also have successfully converted the files to be entirely lowercase and without punctuation. Aug 22, 2012 · That depends on your needs. Oct 8, 2013 · char[]-strings in C are usually null-terminated. txt to the end of a second file myfile2. May 4, 2014 · “while( !feof( file ) )” is always wrong. The data is read from the file in the same form as it is stored i. WriteLine("is some text") sw. It’s like the signal that tells your program, “Hey, nothing more If you're typing at the terminal and you want to provoke an end-of-file, use CTRL-D (unix-style systems) or CTRL-Z (Windows). Commented May 12, 2011 at 21:59. (About fsize, see update below. size: the size of each element to read(in Oct 27, 2011 · The key point is that, at the best of my knowledge, you cannot know that a file is come to end without trying to read it. There are other methods of reading text based files, but here I am concerned with fread() only. Reading a Line From File using fgets. To have a flexible code and avoid unwanted effects just apply any solution given by other users. ungetc() returns c on success, or EOF on error. Reading integers from a file. Reading a text file line-by-line. You should instead read values from the stream, with fscanf() for a quick and dirty throw away toy program, or with fgets() for a more robust parser: Jun 5, 2023 · The problem lays on the behaviour of feof() and the way you are using it. Sep 9, 2021 · I am writing a code which reads a binary file, read each struct fields seperatly, prints out the results, then stop when the file reading reaches the end. In fact, you can use this to calculate your count variable. And that is not all. Read the entire file into that buffer -- you can probably use fread() to read the file all in one shot (assuming the file is small enough). Let's say, 1024 bytes per chunk. We can Mar 21, 2012 · I guess the man page does not spell it out, but to me it would make no sense to read a bunch of bytes but return a different length, so presumably the 2nd to last call to read would read data up to the end of the file, returning the number of bytes read as usual, and then the next (and final) call to read would return 0 as there is nothing left May 8, 2013 · The only explication I can possibly think of for your results is that your file has some character with bit 7 set at the end of the file, that the implementation is returning a negative number for this (but not end of file, because it is a character), which results in an out of bounds index in values[val], and that this out of bounds index TL;DR - using file descriptors, fstat and read was the fastest and using file streams and seek was the slowest. Here I am reading data in a 2d char pointer but the method is the same for the 1d also. In C, EOF is represented by the EOF macro, which has a value of -1 (or FFFFFFFF in hexadecimal). end of file. – Mats Petersson. eof()) as eof() will only be set after reading the end of the file. Some other functions return the number of items read; for example, the read() function returns 0 to indicate end-of Nov 19, 2014 · I tried this after reading the file programe get closed. r+: Open for both reading and writing. gcount() // Charecters readed from input. ) The simplest solution is to change this: while(!feof(fp)) to this: while(1) and this: Oct 14, 2024 · In C++, EOF stands for End Of File, and reading till EOF (end of file) means reading input until it reaches the end i. Jan 27, 2018 · string[] lines = System. dll"); if you want to be able to seek first (e. ab: Open for append in binary mode. (That is: it doesn't tell you when you've read the last character; it tells you when you've read past the last character. seekg (0, ios::end); To get the length of the file (when at the end), use tellg which returns the absolute position of the get pointer. Here's my code: FILE *pFile; FILE *p Mar 27, 2012 · To go to the end of the file: ifstream is; is. The idea of getting the size of the file and doing one alloc is still the same). OK. May 24, 2017 · fgetc(), getc() and getchar() return the character read as an unsigned char cast to an int or EOF on end of file or error. Jun 24, 2024 · In C, reading a file line by line is a process that involves opening the file, reading its contents line by line until the end of the file is reached, processing each line as needed, and then closing the file. May 20, 2014 · I have csv file input where I read in multiple lines which contain multiple fields related to that line. – lurker. I know that initially the document has 16 rows, and that's why I designated int noRows = 16; in my main funtion. Dec 12, 2016 · I have small problem with my C code. In C, the end of string is represented by this caracter. In C++, files are mainly dealt by using three classes fstream, ifstream, ofstream available in fstream headerfile. IO Imports System. Jan 3, 2015 · In the case where you don't know how much data is in the file, it is worth to use a WHILE loop with the condition that you perform the while loop until it reaches the end of the file. Then after all the input has been read, getchar() will return EOF, and hence getchar() != EOF will be false, and the loop will terminate. Oct 24, 2011 · I have a text file like this : Sting Another string 0 12 0 5 3 8 Sting Another string 8 13 2 0 6 11. org Feb 2, 2024 · The fgets() function reads characters from the specified file stream until one of the following conditions is met: a newline character (\n) is encountered, n - 1 characters have been read (maximum number of characters specified by the second argument), or the end of file is reached. Jul 26, 2010 · Unfortunately the read function isn't really suitable for this sort of input. Delete(path) End If Dim sw As StreamWriter = New StreamWriter(path) sw. Apr 23, 2022 · Consider this code to read a text based file. open( "file. should read ghi, def, abc in lines. I have a binary file in little-endian that I need to convert to big-endian, and I don't know how to read the file. Whether it's text or binary data, it's read the same way. it is not showing the last line of file, which should be in the new1 string pointer after complete reading. How it's indicated depends on how you read from the pipe. ofstream: Stream class to write on files ifstream: Stream class to read from files fstream: Stream class to both read and write from/to files. As for appending the new data (the new string) once the file has been reduced in size, just seeking to the end (fseek(file, 0, SEEK_END)) and fwrite()'ing there should do it. When you read binary data from a file, no terminating null-character is read into the string. Oct 17, 2013 · I'm trying to append the contents of a file myfile. Jan 3, 2014 · So, here's my problem: I want to make a program that reads chunks of data from a file. tellg(); To go back to the beginning use seekg again, this sets the position of the put pointer. This loop terminates with string inputs because all characters (even null bytes) are accepted. I want to read in text from the file backwards, buffering it into lines - that is. You can read the whole file (but if you don't read passed the end EOF is not set). g. Jan 23, 2015 · The extra items written after the end-of-file is the left items in buffer written in the last time. fgets to read line by line in files. Jul 3, 2024 · In C, reading input until the End of the File (EOF) involves reading input until it reaches the end i. Following is an examples of the code. Mar 29, 2013 · So I'm not entirely sure how to use fread. Shocker, I know. The second parameter specifies the maximum size of data to read, which should match the size of myString (100). The ANSI-C equivalent of seekg is. Sep 30, 2009 · @sftrabbit: Opps. The getline() function can be used to read a line in C++. So it works correctly for your circumstance. What's the best way to read a file backwards in C? I know at first you may be thinking that this is no use whatsoever, but most logs etc. is. Read File Till EOF in C++The getline() function can be used to read a line in C++. What matters much more is how well the system utilizes real world I/O devices, like hard drives. string contents = reader. Dec 27, 2021 · In C, reading a file line by line is a process that involves opening the file, reading its contents line by line until the end of the file is reached, processing each line as needed, and then closing the file. Reading a File Line b No it doesn't. Let's start with the one concerning your question: First, fileBuffer contains the contents of the file. That's why I got different values when I used strlen(). Presumably you're looping through a file using fgets to get each line. Close() Dim sr As You need to check the return value of fgets. Feb 6, 2024 · What is EOF in C? Alright, so EOF stands for ‘end of file. Text Public Class Test Public Shared Sub Main() Dim path As String = "c:\temp\MyTest. IO. However you do that, they initially reside in memory and / or in CPU registers. WriteLine("Reading") sw. Oct 4, 2015 · @NooB 1) Depends on when you want the file closed. For example my function is reading in a line from a file and prints it out using getchar() while((c=getchar( Apr 25, 2017 · C is designed to be implementable even on file systems that do rather strange and bizarre things. May 5, 2017 · I am reading some data from a file using read. open(filenam I need to read all integers, sort them and write them as a strings to another file. Not all files end with a line feed, yet each iteration of the loop appends "std::endl" to the stream. I can copy the contents, but I can't find a way to append. To make them go from there to a file, you need to send them there. The EOF flag is not set until you read past the end of file. This has significant performance advantages. WriteLine("to test") sw. May 18, 2014 · There is no "end of file character" in a string (or even in a file). Read a file line by line for integers. That's ok, except that printf()'s %s expects a C-string, not the file's content. For example test. seekg(0); // Sets input position indicator. Jun 8, 2010 · @mcabral: That will just stress the CPU, not the I/O system. dat","a"); and then fill it normally by reading the inputs from the user and then write them in your file: example: Jan 12, 2018 · So I have this code that reads a bunch of lines from a csv document. ReadAllLines("file. the strcpy copy string to a sting buffer. This is much faster than single charecter reading of the file. For example, you might set up a thread whose purpose is to read whatever bytes are available from May 6, 2017 · My program is reading the last line of data from an infile twice. Feb 10, 2013 · @Mats Petersson I've been trying to figure out the best way to get the file size, if ifstream already knows the size of the file from the file system, it seems extraordinary to me that we'd have to do something like going to the end of file, getting the size, then returning to the beginning. When I execute the program, the last line of data is being printed twice. if you want only the last 1024 bytes of the file) you can use the stream's Read method. Mar 24, 2022 · You should test the return value from read instead. What is the Jan 9, 2012 · If the width() is 0 when using the formatted input operator with a char array, an arbitrary number of non-whitespace characters is read. Using the file position would be preferable in that case. However, the newline read is preserved. Here is what I has so far but doesn't work exactly. Reading line by line in C. Aug 21, 2012 · When the end of the file is reached, fscanf will return EOF, which the while loop will catch, and no more stuff will be read. Apr 21, 2022 · Open the file in binary mode, seek backwards a few bytes from the end, and then read to the end, remembering whether the last thing you read was a valid line break sequence. Assuming this is some sort of artificial requirement from interview/homework/exercise, you can attempt to simulate line-based input by reading the file in chunks and splitting it on the newline character yourself, maintaining state in some way between calls. Dec 23, 2012 · Either way, using eof to determine end of file is bad, using "try to read and see if it failed" works much better. For the test I ran this on a small Linux box I have running a headless ArchLinux server. int d; while (scanf("%d", &d) != EOF) { … }), then you would get an infinite loop if there was a non-numeric, non-white-space character in the input (e. I'm trying to read till the end of a file for a phonebook app that im converting from C to C++. Ask Question Asked 3 years ago. Sep 17, 2024 · File handling in C is the process in which we create, open, read, write, and close operations on a file. Dec 19, 2021 · Random characters at the end of C read file. If read set 4 characters, printf will read these 4 characters, and will test the 5th: if it's not '\0', it will continue to print until next '\0'. It's my personal choice for reading most disk files. I see the same behavior now. abc def ghi. Dec 6, 2010 · The code below uses a random-access FileStream to seed a StreamReader at an offset near the end of the file, discarding the first read line since it is most likely only partial. Here is what I have so far: FILE *in_ Mar 30, 2012 · That's simply how feof works; it doesn't tell you if you're about to hit end-of-file, it tells you if you have hit end-of-file. It doesn't tell you if you are just at the end of file. Apr 10, 2013 · The following is my solution to the question. string in your example). to perform input, output, and many different C file operations in our program. SEEK_SET - the absolute position from the start of the file SEEK_CUR - the position relative to where you currently are in the file SEEK_END - the position relative to the end of the file May 9, 2014 · I have a text file. We can Apr 30, 2017 · i m trying to read from a file and stop when i hit end of line. Jan 6, 2011 · EOF in C denotes the end of a file, with the getc () function reading a character from a file stream and returning EOF on error or end of file, while the feof () function checks if the end of the file has been reached. I wrote a code, but I read char by char, put the word in an char sub_arr [Max_Int] and when I met ' ', I put these chars, now one string, after atoi-ing it into another Main int array,until reaching the end of the file, string by string, and then I sorted and Mar 4, 2019 · Any idea how do I go about on closing and opening a file only if it has read until the end of the file. When I print the contents of the file, I'm getting random junk on the end. Dec 22, 2014 · Opening the file with the mode a+ (append, allowing reading) sets the file position at the beginning of the file, so the first call to fgets reads the first line. Hence, it is printing "Read could not happen" because you are trying to read an empty file. I am not sure whether there is a more efficient way to solve this question. Use another char pointer to transverse the file from end to beginning of the buffer. This does not work: because if you call: int count = in. But in append mode, all writes are performed at the end of the file. These classes are derived directly or indirectly from the classes istream and ostream. May 22, 2012 · In fact, memory permitting, you can read the entire file into an array and do all of your processing in memory. feof() will return the state of the end-of-file status only after a failed attempt at reading data from the file. We can use this function to read the entire file Mar 30, 2015 · To read the entire contents of a file into a byte array, you only need an array the size of the file. I want to read file until I hit certain character or EOF (from parameter as seen now). Please, make an experiment and delete the new line (thelast character in file) - you will not get the duplication. The code isn't wrong[*], it just doesn't do what you seem to expect. I found a couple of stackoverflow references to seeking X bytes before end of file and then reading forw May 12, 2011 · It tests if the read failed because of an end-of-file condition. May 10, 2020 · There are several problems here. This is unrelated to reading the file contents. Data is added to the end of the file. And if some writer wrote N bytes to this file later, and then the read() will just return min(N, buffersize). At the end of the loop, the variable i contains the number of read data Dec 21, 2022 · Note, that the 'end of stream' state will only be set after a failed read. File. In this article, we will learn how to read a file line by line in C. Commented Jan 23, 2020 at 14:25. If I write an array to the output file and I close the file, then open the file again and read everything until end-of-file is reached, although the file contains only 4 number, the program will read and print 5 numbers, why? Program output: a[0] = 4 a[1] = 7 a[2] = 12 a[3] = 34 a[4] = 34 May 8, 2018 · I'm trying to read patient information from a file, insert the data from the file into fields of a structure, and insert the node into a linked list until I reach an EOF. It does not indicate, that the next read will be the end of the file. Reading a File Line by Line in C Jul 26, 2011 · I would like to read a file line by line from the end. They are one byte longer than necessary, and the last byte is set to 0x00. This can easily overflow the array and become a security problem! Essentially, this is the C++ way of spelling C's gets() (which is now removed from both the C and the C++ standard libraries). ’ It’s like the period at the end of a sentence in a text file, indicating that there’s no more content to read. the thing is, it doesnt seem to work. e. you will notice that count == 0. ) I can get the behavior you describe if I add a second newline character to the end of in. @lh3: CPU overhead does not matter for the IO system. Trying this would jump to the end of the file: fseek(p, 0, SEEK_END); Feb 13, 2017 · The second argument evaluates to an iterator value that represents the end of the file. A proper way to read a text file line-by-line till the end is usually not clear from ifstream documentation. I would suggest you to use "r+" mode, if you are Jan 23, 2020 · It's true after an attempt to read past the end of file. WriteLine("This") sw. length = is. Syntax of fread() size_t fread (void * ptr, size_t size, size_t nmemb, FILE * file_pointer); Parameters: ptr: pointer to the block of memory to read. FYI - The binary file contains multiple re May 26, 2020 · So the conclusion is, all functions read till EOF, but the data type we used to store them can't hold all values. Again, crazy. If a file system doesn't keep track of file sizes accurate to the byte, requiring that implementations do so would likely make them incapable of exchanging data with other programs. EDIT: remember to call fflush() before truncating the file! as I see in your code the type of tempchar is char: char tempchar. ReadAllBytes("file. Feb 6, 2024 · In C++, EOF stands for End Of File, and reading till EOF (end of file) means reading input until it reaches the end i. For example, given the following data file "foo. Nov 10, 2012 · If you consider that your file is a textual file, your must add a '\0' after calling read, for indicate the end of string. Apr 5, 2019 · Bytes written to the write end of a pipe are obtained from the read end of the pipe by reading it. – prelic Apr 26, 2014 · Thinking about it a bit more, you don't need the C program to do any piping, you just need to invoke it once and after that you can open /dev/tty01 from Java. txt")) {// Read entire text file with ReadToEnd. It reads to the end of the input, but you seem to want to read only to the end of a line. How do I write a loop which reads a line of text from the csv file, then keeps looping until it reaches the end of that line. Modified 3 years ago. append the most recent data at the end of the file. After printing the contents of file, it's printing some junk until end of buffer Jan 15, 2010 · In spite of its name, getc returns an int, not a char, so that it can represent all of the possible char values and, in addition, EOF (end of file). Here's a small C program that will do this: Jul 16, 2017 · You cannot use feof() to detect end of file before attempting to read from the file. Commented Dec 23, 2012 at 12:06. The performance difference between the two C++ approaches is minimal and shouldn't make any difference in practice. Return Value: the number of bytes read If the function tries to read at end of file, it returns 0. Current Situation: I have a text file that looks like this: beginning of file more lines with some bizzare spacing some lines next to each other while others are farther apart eof void read_words (FILE *f) { char x[1024]; /* assumes no word exceeds length of 1023 */ while (fscanf(f, " %1023s", x) == 1) { puts(x); } } If you don't know the maximum length of each word, you can use something similar to this answer to get the complete line, then use sscanf instead, using a buffer as large as the one created to read in the Mar 5, 2014 · It would be more accurate to call it an end-of-file condition. Imports System. Should restructure the while loop to account for this. In your example you should probably check the return value of scanf and if this indicates that no fields were read, then check for end-of-file. i have a program that reads from file(with multiple lines) and reading stop Nov 26, 2024 · (See also the std::fs::read convenience function for reading from a file. – Aug 1, 2010 · Use fsize to get the size of the file you are reading. Feb 6, 2017 · I am trying to read a text-file based using the &gt;&gt; stream operator, but this seems to read the file word by word: void printFile(char filename[]) { ifstream input; input. byte[] data = System. Reading an indefinite Aug 31, 2009 · The txt file is structured in groups of 5 lines of data that are supposed to be read into vector orders. Meaning if you want to read a string and get something nicely null-terminated, you need to handle that yourself. 0. This might be a problem if our fseek doesn't support the SEEK_END origin when the file is opened in binary mode. You only get an EOF on the read end of a pipe when all descriptors on the write end are closed. Dec 20, 2022 · @cnicutar and @Pete Becker have already pointed out the possibility of using noskipws/unsetting skipws to read a character at a time without skipping over white space characters in the input. It reads upto newline or end of file. while ((ch = fgetc(fp)) != EOF) { printf("%d) %x \n",y, ch); payload[y++] = ch; printf(" %x \n", arr[(y- 1)]); } Mar 18, 2014 · What happens in the while loop when the end of file is reached and the read on line 43 becomes invalid? The way your program is structured you do not see the problem, but it is there. It's also a source May 17, 2017 · In C++ (and you added the C++ tag) you can write a function accepting an arbitrary input/output stream. Jul 9, 2015 · Instead of fgetc() you can use fgets. – user2100815. So I read the first 1024 bytes, perform various operations and then open the Oct 12, 2016 · You'll need to call fileno() on the FILE * structure to get the file descriptor for ftruncate(), though. When open the file, I use ios::ate to set the file position to the end of the file and use seekg method to read back. Feb 27, 2014 · Sure: The fseek()-ftell()-rewind() block is a rather standard way of obtaining the size of the file you are about to read; this way, you can dynamically allocate the size of your memory buffer to be exactly the same as the file size, no more and no less. So the first call to fputs sets the file position to the end of the file, then writes df. So far I have tried: C# program that uses StreamReader ReadToEnd using System; using System. txt"); If it's a binary file, you can use ReadAllBytes. I've been Jan 27, 2015 · I've wrote this short code to read a text file and copy its information to a new txt file, but doing some character substitution in the process. At the end of the last line, you have a new line character, which is not read by >> operator and it is not an end of file. #include &lt;iostream&gt; #inc Sep 3, 2015 · How would I be able to reset a pointer to the start of a commandline input or file. If a read has been successful, fgets returns the pointer to the buffer that you passed to it (i. Read File Till EOF in C++. txt" Try If File. The problem i'm having is trying to terminate my while loop when I reach the EOF. Reading a File Line b Oct 11, 2024 · We can also use file buffer member function to determine the length of the file. char *readUntil(FILE *stream, char character, size_t *length) I used thi Apr 10, 2013 · Allocate a buffer pointer to the file size obtained in #1, above. The performance of the C code is what makes the benchmark impressive and can be a game changer in terms of speed. Something to be careful of here is when you're reading from files that have been piped in via stdin, is that this and most of the answers given will append an extra line feed on the end of your input. txt: Jun 26, 2009 · Besides the usual seek-and-read techniques mentioned above, you can also map the file into your process space using something like mmap() and access the data directly. I am writing a program to read from the file using fgetc and put in a two dimensional buffer. Thus, when the pointer is at the last character, it will return EOF. As I explained, this std::string constructor takes two iterators as parameters: the iterator to the beginning of a character sequence, an an iterator to the end of the character sequence. The difference here is the formatted input operator>> is actually reading passed the end of file to find the end of Feb 25, 2017 · I open the file, malloc enough memory to store the contents of the file and then read the contents of the file into that memory. That is the reason why I check feof() and ferror() after having read data. Close() Dim sr As May 31, 2010 · You can use fseek to move to a random position within a file. ) §Implementing read_to_end. Enter file : 1. Use this size to do one alloc of memory only. Viewed 1k times 0 . int fseek ( FILE * stream, long int offset, int origin ); Where origin can be SEEK_SET, SEEK_CUR, SEEK_END. This may not be an issue in most cases, but Mar 6, 2014 · In C++ I usually jump to the end of the file using ifstream::seekg and giving it the ios::end argument for position. tunzkx abgxzth oalzzm iurgxrcx emxru uly efvtyz tbs zgolfp xwchc