CSCI-E28                    Lecture 3                     Outline
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          Topics:   Directories, File Attributes, Bits, File Operations

          Approach: Write our own versions of Unix programs

          Featured Commands:
                    ls, ls -l

          Main Ideas:
                    A directory is a list of file names
                    File attributes can be numerical values
                    File attributes can be yes/no settings
                    Bitwise operations ( |, & )

          Agenda
                    stdio          fopen/getc/putc/fclose vs open/read/write/close
                    ls1            opendir(), readdir(), closedir()
                                   not sorted, and does not support -l
                    file attributesowner, dates, size, type, permissions
                                   look at chmod(), chown(), chgrp(), touch
                    stat1          stat() system call
                    stat2          coding yes-no attributes as bits
                                   binary, octal, bit operations
                    ls2            combine ls1 and stat2
                                   still not sorted, and what about ls -l filename

          Sections
                    0. First, one more item about buffering:
                        * people asked after class about using open,read,write,close
                          vs fopen, getc, putc, fclose -- what's the difference?
                        * Answer - the standard library adds buffering
                          a FILE points to a struct containing a (a) ptr to a buffer,
                          (b) some pointers to keep track of where we are, (c) file
                          descriptor, (d) type of open(read/write/both)
                          Thus, getc or fgets do what our utmplib do.
                          The include file <libio.h> line 271 has the def

                     1. files have content AND properties
                     2. Using ls
                     3. A brief review of the Unix directory tree
                     4. Is this just like who? open, read, show, close
                     5. What is a directory?
                     6. Reading a directory
                     7. How close are we to a complete version of ls?
                     8. How do we add the -l option?
                     9. How does stat() work?
                    10. What info do we need from what stat tells us?
                    11. How do we decode the type and file permissions?
                    12. How do we convert uid to logname?
                    13. How do we convert gid to group?
                    14. Building stat2.c : format info just like ls -l
                    15. Can we combine stat2.c with ls1.c ?