File Systems and Permissions

To ensure the security of the files used by the new Web site, files need to access controls that limit which users can view and execute them. To further your understanding of file permissions, describe in detail these 5 file listings, explain all items on each line, explain what they specify or mean, and give the chmod command to set files with these permissions:

1. -rwxr-xr-- 1 instruct staff 270311 Aug 11 2009 install.sh
2. -rw-r--r-- 1 instruct staff 348039 Aug 12 2008 User_Guide.txt
3. -rw-r----- 1 instruct staff 635106 Aug 12 2009 Admin_Guide.txt
4. drwxr-xr-x 4 instruct staff 144 Aug 12 2009 Documents
5. -rwsr-sr-x 1 nobody nobody 169202 Aug 11 2009 httpd

It is also a necessity to know and understand regular expressions, not only at the UNIX command line, but editors and some programs use them quite extensively.

Explain the following Metacharacters/Regular Expressions:

• *
• ?
• ^
• $
• [0–9]
• [a–z]

Give a regular expression to match the following:

• All files that end in txt
• Files that have a second character of a and end in sh
• Any file that starts with a number
• A blank line
• A traditional 10-digit U.S.-based phone number, in the following format:
  • (407) 555-1212

Submit the explanations, commands, definitions, and expressions in a Word document.