Lecture 4 CSCE 510 - LS Implementation

• AR - archive and library maintainer
  • Why is it needed?
  • Syntax: ar -option [ posname ] archive file1 ...fileN
• man 5 ar

       A file produced by ar has a magic string at the start, followed by the
       constituent files, each preceded by a file header.  The magic number and
       header layout as described in the include file are:
  
       struct ar_hdr {
               char   ar_name[16];
               char   ar_date[12];
               char   ar_uid[6];
               char   ar_gid[6];
               char   ar_mode[8];
               char   ar_size[10];
               char   ar_fmag[2];
       };
  

• AR options
• suboptions
• File Times
  • st_atime "last access time" (ls -ul)
  • st_mtime "last modification time"
  • st_ctime "last inode change time" chmod, chown, (ls -cl)
  • int utime(const *path, struct utimbuf *times)
  • AR program due Sept 16 midnight
  • Function documentation
    • function header
    • Author, Data, Modifications
    • preconditions
    • postconditions
  • File Times
  • int utime(const *path, struct utimbuf *times)
  • Umask
  • User IDs: real and effective
  • SET UID bit
  • Notes on Permissions : new file owner/group
  • File systems
    • 1.boot block
    • 2.super block
    • 3.inode table
    • 4.data blocks
  • Disk partitions/filesystems diagrams
  • inode data block pointers
  • File Systems: adding a directory
  • Creating Directories

      #include 
    
      #include 
    
      int mkdir ( const char *path, mode_t mode );
    
    

  • chown
  • links
  • rm command / unlink system call
  • hard links vs symbolic links
  • Manipulating Directories
  • /usr/include/dirent.h

            struct dirent {
            ino_t d_ino;
            char d_name[NAME_MAX + 1];
            }
    

  • directory functions
    • DIR *opendir(const char * path)
    • struct dirent *readdir(DIR *dp)
    • void rewinddir(DIR *dp)
    • int closedir(DIR *dp)
    • int rmdir(const char *path)
    • mkdir
  • Example: list_dir.C
  • LS - man ls
    • /usr/bin/ls [-aAbcCdfFghilLmnopqrRstux1@] [file...]
  • ls1.c
  • Sorting
  • tsearch trees
    • node declaration
    • compare function
    • traversal orders:
  • tsearch.ex.c (even better man tsearch)
  • tsearch trees

  [Readings:]

  [Assignment:]

  Program 1 due Sept 14 - LS
  

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  URL = http://www.cs.sc.edu/~matthews/Courses/510/Lectures/lec4.html