I/O Basics

• You should read chapters 4 and 5.
  • These are very technical with lots of detail.
  • You should do a first pass read to the the "feel" for the subject.
  • As we cover the material you should go back and read again for content.
  • I understand that there is way too much detail to get everything, but you need a foundation.
• This is system level I/O
  • C++ style iostreams are built on top of this.
  • C style scanf, printf, ... are built on type of this
• There are four basic system calls, plus a number of others.
  • int open(const char *pathname, int flags, mode_t mode); and variants.
  • int close(int fd);
  • ssize_t read(int fd, void *buf, size_t count);
  • ssize_t write(int fd, const void *buf, size_t count);
• All in part 2 of the manual
  • man 2 open
• Open is the most complex, with many many options and many ways to fail.
• Close is the easiest, one argument, only three errors.
• We will study these in more detail in the next set of notes.
• A modified example of code using these commands.