Read integers from a file

Read integers and appends sum to the end Write a C program read integers and appends sum to the end in File Handling. Notify of. Oldest Newest Most Voted. Inline Feedbacks. AMP TV free online. In particular the sequence of characters that fscanf reads from the file must match what it is expecting from it's format string.

The function can fail if it encounters unexpected characters like say an alphabet. You can and should check the return value of fscanf after every call to it, before proceeding.

If you use atoi be aware that it produces undefined behaviour with certain values and does not indicate failure. The functions strtol and strtoul are really much more robust. Also you could read the file character by character with a function like getc and do the conversion to a int value yourself, but it's usually better to use standardised functions unless you're learning or have special requirements.

Please provide us with the code for your attempted solution and an exact description of the format of your text file to help you further. Show your code. If the integers are stored as text in the given file, you can read them in a buffer and parse the individual items using sscanf. If you want to directly go for fread, then it more or less requires that the data be written in the same format by fwrite or something owing to the endian-ness and the variable size of data types.

No one likes to write code to explain something to someone. It would be far easier for everyone if you post your own code snippets. I think pete might disagree with you there. If you have any questions about the code, I'll answer them as best as I can. File values: , , , 72, 14 File is closed. Array values: 3, 1, 3, 1, 3 File is open for reading.

Reading file into a linked list File is closed. File is open for writing. Overwriting file with product of list and array values List is freed. File is open for reading. File values: , , , 72, 42 Line reading buffer is freed. File is removed. Could be as follows: but fscanf can catch the overflow or a wrong input? Keith Thompson. C99 7. So I'm trying to read in an integer from a file and then do some operations in it, for the sake of the problem I'm just trying to output it here:.

EDIT: I forgot to mention, it works as a string, it reads the correct number, but I can't do any operations on it, also if I set the number type to double it works but outputs some random number in the millions Also you either need to initialise number or do a return if you are unable to open the file.

Linux Programmer's Manual. C library function - fscanf. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Reading integers from a file in C [duplicate] Ask Question. Asked 9 years, 3 months ago. Active 2 years, 8 months ago.