Task: System Call Wrappers

Enter the chapters/software-stack/system-calls/syscall-wrapper/drills/tasks/support/ folder and go through the practice items below.

1. Update the files in the support/ folder to make read system call available as a wrapper. Make a call to the read system call to read data from standard input in a buffer. Then call write() to print data from that buffer.

   Note that the read system call returns the number of bytes read. Use that as the argument to the subsequent write call that prints read data.

   We can see that it’s easier to have wrapper calls and write most of the code in C than in assembly language.

   Quiz

2. Update the files in the support/ folder to make the getpid system call available as a wrapper. Create a function with the signature unsigned int itoa(int n, char *a) that converts an integer to a string. It returns the number of digits in the string. For example, it will convert the number 1234 to the string "1234" string (NULL-terminated, 5 bytes long); the return value is 4 (the number of digits of the "1234" string).

   Then make the call to getpid; it gets no arguments and returns an integer (the PID - *process ID- of the current process).

If you’re having difficulties solving this exercise, go through this reading material.