Computer Systems: A Programmer's Perspective (3rd Edition)
Computer Systems: A Programmer's Perspective (3rd Edition)
3rd Edition
ISBN: 9780134092669
Author: Bryant, Randal E. Bryant, David R. O'Hallaron, David R., Randal E.; O'Hallaron, Bryant/O'hallaron
Publisher: PEARSON
Question
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Chapter 11, Problem 11.10HW

A.

Program Plan Intro

IP addresses:

  • The IP address denotes an unsigned integer that is 32-bit.
  • The IP addresses is been stored by network programs in IP address structure.
  • The addresses present in IP address structure are stored in network byte order.
  •  An unsigned 32-bit integer is transformed from host byte order to network byte order by “htonl” function.
  • An unsigned 32-bit integer is transformed from network byte order host byte order by “ntohl” function.
  • The IP address is presented to humans in a form known as “dotted-decimal” notation.
    • Each byte is been represented by its corresponding decimal value and is separated by a period from other bytes.

Passing program arguments to server:

  • The arguments for “GET” requests are passed in the URI.
  • The character “?” separates filename from the arguments.
  • The character “&” separates each argument.
  • The arguments do not allow spaces in it.

Server passes arguments to child:

  • The server calls “fork” to create a child process and calls “execve” to run program in child’s context once it receives a request.
  • The child process sets CGI environment variable values.
  • The “adder” program can reference it at run time using “getenv” function of Linux.

Output is sent by child:

  • The dynamic content of a CGI program is to be sent to standard output.
  • A CGI program sends dynamic content to standard output.
  • It uses “dup2” function for redirecting standard output to connected descriptor associated with client.
  • The result written to standard output by CGI program, it goes directly to client.

B.

Program Plan Intro

IP addresses:

  • The IP address denotes an unsigned integer that is 32-bit.
  • The IP addresses is been stored by network programs in IP address structure.
  • The addresses present in IP address structure are stored in network byte order.
  •  An unsigned 32-bit integer is converted from host byte order to network byte order by “htonl” function.
  • An unsigned 32-bit integer is converted from network byte order host byte order by “ntohl” function.
  • The IP address is presented to humans in a form known as “dotted-decimal” notation.
    • Each byte is been represented by its corresponding decimal value and is separated by a period from other bytes.

Passing program arguments to server:

  • The arguments for “GET” requests are passed in the URI.
  • The character “?” separates filename from the arguments.
  • The character “&” separates each argument.
  • The arguments do not allow spaces in it.

Server passes arguments to child:

  • The server calls “fork” to create a child process and calls “execve” to run program in child’s context once it receives a request.
  • The child process sets CGI environment variable values.
  • The “adder” program can reference it at run time using “getenv” function of Linux.

Output is sent by child:

  • The dynamic content of a CGI program is to be sent to standard output.
  • A CGI program sends dynamic content to standard output.
  • It uses “dup2” function for redirecting standard output to connected descriptor associated with client.
  • The result written to standard output by CGI program, it goes directly to client.

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