Final answer:
To read input from a file, evaluate expressions, and print the output inside the file in C, you can use file handling functions and string manipulation.
Step-by-step explanation:
To read input from a file, evaluate expressions, and print the output inside the file, you can write a program in C using file handling functions and string manipulation. First, you need to open the input file using the fopen() function, then read the expressions line by line using the fgets() function. Next, you can use libraries like math.h to evaluate the expressions. Finally, you can open the output file using fopen(), and write the evaluated output using fprintf().