Fscanf while loop It checks if all three inputs (ID, salary, and name) are successfully read by confirming that three items ( 3 ) are processed. Isn't that how I would frame a while loop using fscanf to read a file? Yes, apart from the fact that dicitonary is not a suitable buffer. Jun 5, 2022 · I am trying to read a file using fscanf with a while loop: 1) name 2) surname 3) age 4) unit 5) Random_Numer 6)Doctors my problem is how can i save them in structure using fscanf (example: patient(i). in VSCode and Jan 29, 2018 · So should my code look something like this: fscanf, then perform check with the while loop, do the operations, then right before the end of the for loop, fscanf again? – Freedom Commented Jan 29, 2018 at 6:26 Mar 12, 2025 · While it’s commonly used for reading formatted data, it can also be adapted for reading line by line when combined with some additional logic. compared to the file what i fopen, it just read the first 9 lines. The printf statement is then user to print the data read from the file. h&gt; # Jun 3, 2012 · problem with fscanf inside while loop in c-language. The fscanf() function in C reads formatted data from a stream, interpreting input based on a specified format. The problem with using fread is that my file pointer will be moved each time the condition is checked in the while loop. fscanf() Function. May 8, 2018 · The problem i'm having is trying to terminate my while loop when I reach the EOF. h> header file. As no data was read, previous values are printed in each loop iteration. Stuck in a fscanf loop. To read values from a file, you can make use of the fscanf function. i couldn't figure out why this happens. Note that the loop mentioned by user208785 in the comment above should be int c; while ((c = getchar()) != EOF && c != '\n') ; — The type of c should be int and the code needs to test both EOF and newline, though the code will normally get a newline before EOF. The while loop doesn't skip the scanf() function the first time through the loop though. 3 in the file? Mar 12, 2025 · While it’s commonly used for reading formatted data, it can also be adapted for reading line by line when combined with some additional logic. 上記ソースを C:\2014\0628\003. Essentially, I want to code to first check the text file log for any previously encountered prime numbers, but no matter what I put for the while-loop containing fscanf(), it seems like my code never enters it. Input Value read : 25. ---This video is based on the question ht May 11, 2013 · C program, fscanf used to transfer variables from . This tutorial guides you on how to use the fscanf() function in the C program. Commented Jan 30, 2015 at 10:06. Jun 20, 2012 · The fact is that fscanf() itself has a return value; if the file ends it will fail to do the requested scanning, and it will tell you so. so how can i loop the the fscanf?(assuming that i don't know how many lines are in the file? or maybe its safe to say to loop the fscanf until EOF?) thanks a lot! May 4, 2015 · I have been searching around the forum and man fscanf about information on return values of the function and what I found is that fscanf returns the number of successfully matched values. Request to precept it and provide solution Regards and Thanks. That is still not enough information to us to help you. Especially functions as prone to failure as *scanf(). Jan 10, 2025 · Output. If fscanf fails (returns 0), then data[i] will remain unassigned. If the conversion was using a numeric type (e. fscanf not returning EOF or fscanf going to infinite loop in C. It will even return the special constant EOF if the file ends. May 28, 2017 · Using a while loop and the function fputc() to store a string or a character array in a file will make the program more complex and a bit inefficient as well. So just loop on the return value of fscanf(): while( fscanf(fin, "%s", letta) == 1 ) { /* Process, parse, store or do whatever with letta. Jul 21, 2014 · fscanf while-loop never runs. I once traced what a (certain type of) i/o does all the way from the linux read(2) system call through the filesystem, into the block layer, scsi layer, low level scsi driver, to the device, back into the device interrupt handler, and back up all the way to userspace. Put having 2 fscanf's causes a new line everytime and skips half of my data. Please refer to the man pages for more detail. Mar 4, 2022 · problem with fscanf inside while loop in c-language. fscanf inside a loop. i would like to read also the other data from line 2 and line 3 and solve their sum respectively. EDIT when I followed the advice in my own comment below (take the input file and do a hex dump) using the numbers you had above (originally I had just typed Nov 26, 2015 · You should check the functions you call for potential failure. How does the while loop with the fscanf work exactly? Does it read line-wise, character-wise, or something else? fscanf reads data from the stream and stores them according to the parameter format into the locations pointed by the additional arguments. 7 Example Output = Customer 1 has spent 2. dictionary is a small string holding the file name that you're going to read from, you can't re-use it to hold words from the file as well. Oct 11, 2013 · In your case, it may mean that no conversions may have been performed in second call to fscanf, becaude of malformed data in file etc. 22 or -5. 0. Jun 15, 2012 · In reply to Neddy:. Here’s how you can do it: Method 1: Reading Lines with fscanf. This function is implemented in file-related programs for reading formatted data from any file that is specified in the program. Dec 2, 2013 · This is probably why your code was actually going into an infinite loop - and why the second method (which exits the loop when fscanf did not successfully read exactly one value) will work. C fscanf() function reads formatted input from a file. 1. 1 C - fscanf in while loop skips user input. Please put in the effort as descriptive as possible. I hope you know what you're doing. 05, 1. ' char str[100]; //string variable while( (fscanf(stdin,"%s", Iteration Statements/Loops: for, while, do-while; Jump Statements; Linked lists; This is just a test file to be used by fscanf() This is the main function: How is the while loop used in the fscanf function? In lines 22-26, the while loop is used along with fscanf function to read the formatted data in the file and stores them in the variable name, roll_no and marks. g. Therefore, to avoid these we have another function fputs() which directly copies the whole string to the file without the use of any loop. However while the loop is being executed, the value of cmp is equal to 1, rather than 5. Mar 6, 2015 · problem with fscanf inside while loop in c-language. I have to call an fscanf function inside of the while loop, so I cannot have the file pointer changed in the while condition. This function is declared in the header file <stdio. c としてコンパイルして実行する。 Sep 27, 2024 · Here, the while loop uses fscanf() to read each entry until it reaches the end of the file. Related questions. the input not matching your format string, which makes *scanf() return early without advancing the position in the file. Jan 30, 2015 · Your while loop condition is incorrect. Similarly, if you write %*d it will ignore integers until the next space or ne It's complicated. That said, I really don't see much point of the whole loop, as you'll be creating a new local variable aPlayer every time you enter the loop. – Mar 29, 2017 · Please note that fscanf returns an integer which can indicate EOF when the End of File is reached. I am currently trying to solve why the while loop never detects the EOF. The code works, but I don't understand the process behind it. The three changes from your original: The three changes from your original: length-limit what gets read in - I've used 27 here as an example, and unfortunately the scanf() family require the field width literally in the format string and can't use the Nov 25, 2012 · Secondly, fscanf returns EOF at the end-of-file. In C++, you can include <cstdio>. You're probably looking at a match failure, i. Apr 12, 2019 · problem with fscanf inside while loop in c-language. Archived post. txt file 10 ; read old basic files into vb6 2 ; fscanf newline vs space 4 ; Netbeans: How to Create JFrame Object in FrameView subclass 2 ; fscanf vs fgetc 7 ; c# change the color of the particular part of an image 6 ; C++ nest loop program - Help 18 ; Pure C# InputBox 0 ; c++ loop fail 5 ; class 2 Apr 9, 2020 · fprintf function is running fine but a consequent fscanf is not. "while true" is an infinite loop. e. Jun 28, 2014 · fscanfとwhileを使ったテキストファイルの入力 ただし、1文のサイズが20以下とする. As you can see from the 2nd part below, the . 9 3 2. Nov 12, 2018 · Im am trying to use fscanf to read through a file of hex numbers that either have a char followed by numbers or just numbers and no char. #include &lt;stdio. Jul 27, 2020 · In lines 19 and 20, we have two printf() statements which prints "Testing fscanf() function: \n\n" and "Name:\t\tRoll\t\tMarks\n" to the console. #define STOP '. 3 2 5. Your code will have to modified like below: Nov 20, 2018 · EDIT: With the help of members here I have updated my code. If the content of the file does not match the format then the function stops reading at the point where the first mismatch occurs. It stores the extracted values into already allocated memory locations using additional arguments. Mar 25, 2014 · This is part of a much bigger program to make a filmgenie and for some reason the program crashes as it reaches this while loop and i don't understand what my problem is. We would like to show you a description here but the site won’t allow us. As no data was read, file handle has not advanced, so end-of-file hasn't been reached, which in turn explains why loop does not terminate. What is a better way to check for an EOF in a while loop? Can someone walk me through on how does the fscanf work on this particular example (also what EOF represents). The fscanf appears to work for the first line of the file but Check When the End of a File is Reached in C. Infinite loop when using fscanf. 2. h&gt; # But then I remembered that there's a fscanf function: That is why you should use the while loop I mentioned first. Oct 19, 2020 · hey guys i hope you are all well. May 2, 2016 · I'm working on a project, and I can't seem to figure out why a piece of my function for finding prime numbers won't run. Here is the syntax of the fputs() function: I would just do this for your loop condition: while (fscanf(fpointer,"%f, %f, %f, %f", &grade1, &grade2, &grade3, &check) == 4) fscanf will return the number of arguments it successfully read. txt file to fscanf from has only 6 strings,so the fscanf should only loop 6 times and then it reaches EOF. fscanf() stucks in an infinite loop. I don't need an increment counter for [i] in my function returnStats(). the gdb output: I am facing problems looping a fscanf. The fscanf() function is defined in the <stdio. 99 (repeated for all customers) I simply need a way where my loop will repeat my fscanf and print statements all the way to the end of the file. コンパイルと実行結果. My text file is (there are [spaces] in front of every letter): L 10,4 S 18,4 L 20,4 S 28,4 S 50,4 What I Apr 3, 2013 · So I run the program, it does the prints, reads the char I type from the keyboard, switches to the appropriate case, but instead of returning to the top of the loop and stopping at the fscanf in order to receive further input, it acts like it already received a new line or something and switches to the default case, returning to the top of the May 27, 2013 · Secondly, some people would read the second version in terms of while([function]), instead of while([return value]), and be momentarily confused by testing a function, when what is clearly meant is testing the return value. The simplest way to determine when the end of a file (EOF) is reached in C is by using functions like feof(), checking the return value of input functions such as fscanf(), or reading character-by-character with fgetc() until they indicate EOF. I found this interesting and I can't seem to figure out why. Explanation: The %*s in scanf is used to ignore some input as required. C - fscanf in while loop skips user input. i couldn't handle for about 2 hours. h>. if i remove the while loop, the fscanf reads only the first line. What happens if there are floating point values, such as 0. Jun 30, 2016 · I am in a bit trouble, I am asking input from keyboard using fscanf() library function using stdin stream. 5. Learn how to read pairs of numbers from a text file using fscanf() effectively within a while loop in C programming. That is a habit you should get into. 2 Oct 19, 2023 · The while loop I am using now does not work, any fixes or ideas to how I could repeat the fprintf until the end of the file? Example Input = 1 2. 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. This can be completely a matter of personal preference, and as far as I'm concerned, both are valid. i have gdb the excutable obj. In this case, it ignores the input until the next space or newline. Thirdly, scanf reads from standard input, which never ends when it is reading from keyboard. The loop will be exited by the "break" statement in the "if" inside the loop. I used a fscanf to read each line of the file, and another one to check for end of file. It runs into infinite loop at while statement with fscanf not equal to EOF and with NULL only one record when more than one record have been entered through fprintf. Apr 30, 2017 · If you try while( fscanf( f, "%27[^\n\r]", cLine ) == 1 ) you might have a little more luck. You can use Mar 9, 2014 · 1. . ----- 1)John 2)Noah 3)40 4 c - fscanf while-loop 从不运行-我正在做一个项目，但我似乎无法弄清楚为什么我的一段查找素数的函数无法运行。本质上，我想编写代码以首先检查文本文件日志中是否有任何以前遇到的素数，但无论我为包含 fscanf() 的 while 循环放-6ren Sep 20, 2013 · problem with fscanf inside while loop in c-language. In lines 22-26, the while loop is used along with fscanf() function to read the formatted data in the file and stores them in the variable name, roll_no and marks. i found that when execute the while loop to read the line 10, fscanf would return 1, but 3 what is expected. How to correctly use fscanf in a while loop? 0. 2 scanf in while loop. 3*2. doctor) so it stops reading when it starts to read the new patient and stores it for example (day 1=doctor1 doctor2). The fscanf keeps reading until EOF is encountered. After the first call, the fp points to the first newline in your file, so you have to "swallow" that, else fscanf doesn't read anything: fscanf(fp,"%[^\n]\n",s); Note that this also shallows space and tab characters. Follow This loop terminates with string inputs because all characters (even null bytes) are accepted. i'm trying to count how many times the fscanf function reads from a file. Probably what is happening is that after the final line is read, the file position is at the last newline or something rather than EOF. – user694733. fgetl() returns a string ("string" is defined as an array of type char) *except* when fgetl() encounters end of file. To read a file line by line using fscanf, you’ll typically use a loop that continues until the end of the file is reached. The format parameter is a string that describes the format of the data that is expected from the file. Improve this answer. As in the code below (focus on the part where the while loop starts), I am looping the fscanf until it reached EOF. Not -1 , but EOF . a letter or a punctuation character). Hot Network Questions May 13, 2021 · problem with fscanf inside while loop in c-language. I have attached fscanf() file Jan 10, 2025 · Output. 3 in the file? Oct 5, 2013 · I'm having some trouble getting fscanf to work properly when reading a text file. 4. Share. Specifically in the while loop which scans until the End of file. Similarly, if you write %*d it will ignore integers until the next space or ne Nov 9, 2010 · while (!feof(fp)) feof returns a non-zero value at EOF, not necessarily EOF. scanf(3) Library Functions Manual scanf(3) NAME top scanf, fscanf, vscanf, vfscanf - input FILE format conversion LIBRARY top How to read values from a file using fscanf. New comments cannot be posted and votes cannot be cast. Then, your call to fscanf reads up to a newline. You say the while loop does not stop. Reading a FILE and using fscanf goes into an infinite loop. ewud mccz ahux wxiidm batri rkuefi axyf zjcdwl skxfe ibxv