CS201 – Winter 2008 Assignment 4 Due Feb 5, 2008
1. [10 points] B&O, problem 7.9
2. [10 points] Here is a simple program that copies its standard input to standard
output.
#include <unistd.h>
#define BUFFERSIZE 256
int main(int argc, char **argv)
{
int n;
char buf[BUFFERSIZE];
while((n = read(STDIN_FILENO,buf,
BUFFERSIZE)) > 0)
write(STDOUT_FILENO, buf, n);
}
Modify this program so that it takes an optional command line argument
infile. If infile is given, then copy infile to standard output; otherwise
do just what this program already does. The twist is that your program must use
the original while loop (the last two lines of code in main) for both cases. You are
only allowed to insert code, you are not allowed to change any existing code.
You can not write separate while loops for the two cases, and you can not change
the value of any constants such as STDIN_FILENO.
3. [15 points] B&O, 8.17
For # 3, write a small test bed program with a main() function that inputs a
command line from standard input, invokes mysystem(), and prints the exit status
of the child process. Use the test bed to test your function with various command
lines.
4. [15 points] This problem is to help you understand that files do not necessarily
contain ASCII characters. Write a C program called "readdouble" that will do the
following:
a. Initialize an array of 100 double precision floating point values such that
A[n] = n
b. Create a file and write the array to the file, not as character strings but as
an array of 8-byte objects, just as they appear in memory. You don't have
to know what these objects look like, you only have to write them to a file.
You can think of this file as containing a sequence of 100 records, each of
size 8 bytes and each containing a binary floating point value.
c. Seek to the thirty-fourth record in the file; that is, the one whose value is
34.0, and read that record into a double precision variable.
