File Input and Output - Introduction to C Programming for Engineers | CSE A205, Study notes of Engineering

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CSE294A

Introduction to C Programming for Engineers

Lecture

Jeffrey Miller, Ph.D.

File Input/Output

Files are used for data persistence

Files are stored on secondary storage devices, suchas hard disks, CDs, flash drives, etc.

When a file is “opened” in a program, an object iscreated and a stream is associated with the object

For file processing in C, the functions are locatedin the stdio.h header file, so no additional headerfiles are needed

File Open Modes

r

read from a file

w

write to a file

a

append to a file

rb

read from a binary file

wb

write to a binary file

ab

append to a binary file

Sequential File Reading

Here is the code to read from a file sequentially

#include <stdio.h> void main()

FILE

*f_ptr; f_ptr = fopen(“input.txt”, “r”); if (f_ptr

NULL)

printf (“File could not be opened.”); return; } int num; fscanf(f_ptr, “%d”, &num); printf (“number from file

%d\n”, num); fclose(f_ptr); }

Program

Write a file copy program. The program will ask the userto enter the input file and the output file, then will copy thecontents of the input file to the output file.

Homework

Homework #8 is posted!