Files

Notes

• This is 13.5 of the book (sort of)
• int open(const char * path, int flags, int mode)
  • This is a system call
  • The path is the unix path, including the filename
  • flags are a combination of things,
    • But they must include one of :
      • O_RDONLY
      • O_WRONLY
      • O_RDWR
      • See /usr/include/bits/fcntl-linux.h
    • For O_WRONLY: we might specify O_CREAT, O_TRUNC
    • There are other things as well.
  • mode is the permissions for the file
    • But only needed if we are going to create a new file.
  • SYS_OPEN = 2
  • O_RDONLY = 0
• For now I only want to read, so most of these can be ignored.
• This returns a file descriptor (small positive number) or a negative on error
• This file descriptor is what we use when we call read
• int close(int fd)
  • This closes the file.
  • Return 0 on success, -1 on error.
  • SYS_CLOSE = 3
• We have seen the system calls read/write before.