IPC and scheduling

The dup2(oldfd, newfd) function

• redirect IO on oldfd so that they are performed on newfd

• redirect IO on newfd so that they are performed on oldfd

• copies the file descriptor oldfd into the file descriptor newfd

• copies the file descriptor newfd into the file descriptor oldfd

If I call dup2(fd,0) with fd being an opened file

• everything read from STDIN is written to the file

• everything read from STDIN is read from the file

• the file shoud be opened in read mode

• the file should be opened in write mode

When you create a pipe p

• communication goes from p[1] to p[0]

• communication goes from p[0] to p[1]

• you can read from p[0]

• you can read from p[1]

After a dup2(p[0], 0);

• you must close(p[0]);

• you must close(0); (-10)

• you don't have to close anything (-10)

The shmat() function

• allow to create a shared memory segment

• allow to attach a shared memory segment in an address space

• allow to find the location of a shared memory segment

with a pipe p, if p is empty

• write(p[0] ...) will block

• write(p[1] ...) will block

• read(p[0] ...) will block

• read(p[1] ...) will block

with a pipe p, if p is full

• write(p[0] ...) will block

• write(p[1] ...) will block

• read(p[0] ...) will block

• read(p[1] ...) will block

threading allow

• to execute several threads in one process

• to execute one thread in several processes

• to share the process address space between several threads

• to execute each thread within a private address space