Homework #1 - File Dump program in C

Write a C program that gets the name of a file from the command line (as a command line argument to the program), reads in the file and outputs the contents of the file in hex and ASCII, with 8 bytes of the file printed on each line. The output format must match the description given below exactly!

Program Output Format:

Hi Dave.
This is a sample input file.

> mdump sample
0000: 48 69 20 44 61 76 65 2E Hi Dave.
0008: 0A 54 68 69 73 20 69 73 .This is
0010: 20 61 20 73 61 6D 70 6C  a sampl
0018: 65 20 69 6E 70 75 74 20 e input
0020: 66 69 6C 65 2E 0A 00 00 file....
>

• printf(): check the lecture notes or the man page for printf. Note that the "%X" format prints an integer value in hex!

• File I/O: specifically the functions fopen(), fclose(), fread() and feof(). You best source of information is any introductory C text (or web tutorial), but here is some basic information:

  fopen() opens a file and creates a "file handle". The full prototype is:

  FILE *fopen(const char *path, const char *mode)

  The value returned is a pointer to a FILE data structure (defined in stdio.h). You don't need to know much about a FILE data structure - you juse use it later when calling other functions like fread(), fclose(). fopen() returns NULL if things don't work (perhaps the path is invalid).

  path is a string that indicates the pathname of the file to be opened. If the path does not contains any slashes, then it references a file in the Current Working Directory.

  mode is a string that specifies how the file should be opened. To open a file for reading use the mode "r".

  ---

  fread() reads from a file that has already been opened. The full prototype is:

  size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream)

  Note: size_t is special integral type supported by POSIX - you can use an int for this type.

  ptr is a pointer to some place in memory where the data read from the file will be placed. This memory must already be allocated!

  size is the size (in bytes) of each element that will be read. For this assignment you probably just want to read individual bytes (each element is a byte), so size would be 1.

  nmemb is the number of elements that should be read in and stored in memory. For this assignment you probably want to read in 8 bytes at a time (so nmemb would be 8).

  stream is the pointer to a FILE data structure that was returned by fopen().

  The return value is the number of elements read from the file and placed in memory. If this number is less than the requested number, this indicates EOF. A return value of 0 may indicate an error, or may indicate there is nothing left to read, the only way to know is to check using feof().

  ---

  feof() tells whether and End-of-File (EOF) condition exists. The full prototype is:

  int feof(FILE *stream)

  stream is a pointer to a FILE data structure returned by fopen().

  The return value is 1 if an End-of-File condition exists (there is no more to read from the file), or a 0 if there is more data available to be read.

  ---

  fclose() closes a file. The full prototype is:

  int fclose(FILE *stream)

  stream is a pointer to a FILE data structure returned by fopen().

  The return value is 0 on success, any other value indicates some kind of error.

What you need to submit

You should submit your program (the source code for your program), along with a file named README that contains a description of the system you used for development (what kind of machine, what kind of operating system and compiler).

We will compile and run your programs using gcc on a Unix computer, so you should include only code that will work in this environment. Specifically, if you develop the code on a PC using Visual C++ or some fancy environment, you need to make sure that it can compile under Unix (or at least using gcc under Windows).

Part of your grade will also be based on the sample output you provide in your submission. Make sure you run your program on the two sample files, save the output of each to a file and submit these files!

Your grade will be determined according to the following formula:

You should note that you do get some credit for simply including correct output for the two sample files. This means two things:

• If you can't get your program working - you can attempt to build these by hand, although the sample files include non-ASCII data, so you will need to be able to figure out what is in those files.

• If we can't get your program to work on a Unix machine, you can still get credit for the sample output.

• You can do this assignment under Windows using gcc (how we we ever know?), although since you will need to do later programs on a Unix machine you might as well start now...

• The Unix "od" command ("Octal Dump") does something very similar to what your program should do (it does a lot more as well). It may be useful to use "od" to make sure your program is working correctly.

• Make sure your program works with files that are not just plain text! Binary files (perhaps executable programs) should also work. Try running your program on itself! You should be able to see the string literals (constants) contained in your program. For example, if your program includes the statement:

  printf("%4X: ",offset);

  you should see the string "%4x: " show up in the output when you run the program on itself.

• Check the course homepage for a HW1 FAQ - the will evolve as we get questions.