C implementation of Unix commands and system calls

1. cat - concatenates files and prints on standard output
2. ls - lists the directory contents
3. kill - sends a signal to a process
4. wc - prints newline, word and byte contents for each file
5. ps - lists the current running processes
6. rm - removes files and directories (does not delete if the provided file is a directory.)
7. rm2 ./a.out rm file_1 file_2 .... file_n :deletes n files without confirmation. ./a.out rm -i file_1 file_2 .... file_n : deletes n files after the user confirms the deletion. (doesn't check for directory)
8. rm3 does not delete if the provided file is a directory.
9. rm -r does not delete the directory. But goes into the directories and deletes non-directory files.

POSIX Thread library:

1. pthread.c - simple implementation of pthread library