My tar

A Naive implementation of the legendary Tape Archiver.

Build

While in the project root directory, run make to build the binary:

$ make

Run clean to remove /bin/my_tar and .o artifacts.

$ make clean

Usage

$ .bin/my_tar [-cutx] [-f file.tar] file_to_archive ...

Options

• -cf file.tar file_to_archive ... : Archive a file(s) or directory. Multiple files is also possible.
• -uf file.tar file_to_archive ... : Updates archive with new file(s).
• -tf file.tar : Lists files in the tape archive.
• -xf file.tar : Extracts all files in a archive. Existing files in the disk will be overwritten.

When -cf directories, My tar will archive all files within the directory. Sub directories will be tar'ed as directories but their contents will not be included.

Dev options

Option -d <filename> for debug. While in debug mode, the program will skip archiving and print out a ASCII representation of the header produced from <filename>. Example:

./bin/my_tar -d <filename>

example output:

 Field: chksum -- length: 8  -- offset: 148
 |  0  |  1  |  3  |  2  |  0  |  0  |     |  _  |
    
 --
    
 Field: magic -- length: 6  -- offset: 257
 |  u  |  s  |  t  |  a  |  r  |  _  |
    
  (...)

where

• | | represents a memory block of 1 byte. And empty block is an <space> char.
• | _ | is an empty block
• --- is a divider between fields.
• field is the name of the field
• length is the length of a field
• offset is the memory offset of a field in within the header 512 bytes block and

Testing

There is a very basic script to help test some of this programs functionalities. First, make sure you set the permissions accordingly:

$ chmod u+x bin/test.sh

Run test:

$ ./bin/test.sh 

This command will run the program in all its available options consecutively. Appending with -u is not tested in this mode but using the --append option. The script will test My Tar against all file types in the test_files folder. This repo includes fifo, symlink, hardlink, regular and directory file types in test_files.

The script will clean up after itself removing all files.

The script will compile with make and make clean before/after attempting to run the program.

Other available options:

$ ./bin/test.sh --cat file_to_archive ...

--cat will archive a file in both my_tar and the original tar and cat their contents for comparisson. OSX users must install gtar to run the script. Darwin uses bdstar as its defaulttarand gtar ensures we get a consitent tar format.

$ ./bin/test.sh -d file_to_header

Runs in debug mode as described above.

$ ./bin/test.sh --append tar_file_to_apend.tar file_to_append

Use --append for testing th =uf option. Remember that you must pass in an existing file in the archive in other to append using -u.

If you have valgrind and want memory check:

$ ./bin/test.sh --append tar_file_to_apend.tar file_to_append