2019-2020-1 20175320 "Information Security System Design Basics" eighth week of learning summary

2019-2020-1 20175320 "Information Security System Design Basics" eighth week of learning summary

First, the learning content summary

For this week for the system-level I / O way, mainly for a variety of applications called I / O functions were understood, the following is a summary of the contents of this week:

System unified I / O

• Open the file function int open(char *filename, int flags, mode_t mode), which is the process of operational behaviors to flag the file, mode for the access permission bits. The function returns a file descriptor
• Function closes the fileint close(int fd);
• Function to read the filessize_t Read(int fd, void *buf, size_t count);
• Function to write filesssize_t Write(int fd, const void *buf, size_t count);
• Unbuffered readssize_t rio_readn(int fd, void *usrbuf, size_t n); ssize_t rio_writen(int fd, void *usrbuf, size_t n);
• Write buffered ssize_t rio_readnb(rio_t *rp, void *usrbuf, size_t n); ssize_t rio_readlineb(rio_t *rp, void *usrbuf, size_t maxlen);, wherein the buffered row is read from rio_readlineb and rio_readnb additive used, but with the buffer and the buffer can not function without the use of intersecting with the buffer must be based on a function of rio_readthe function
• Function to read file informationint stat(const char *filename, struct stat *buf); int fstat(int fd, struct stat *buf);
• Read the contents of a directory function DIR *opendir(const char*name);and struct dirent *readdir(DIR *dirp);in which actual use requires repeated calls readdir function

Use of man and grep tool

Here I use the read function as an example.
1, using the man -k read | grep 2command to view the read system call.

2, using the man -k read | grep 2 | grep filecommand to further refine the range based on 1.

3, using the grep -nr xxx /usr/includecommand to view the macro definitions, wherein n represents the line number, r represents recursion. Below to view the macro definition of MAXLINE keyword.

Second, the problem of teaching and learning in the process of resolving

This week content for coding practices, textbooks no problems were encountered.

Third, the problem of debugging the code and resolution

Problem 1: Problem teaching operation code appears as shown in Figure 1 when.

Problem 1 Solution: finding is not correct to add header files, operating normally after adding headers.
Question 2: Exercise 10.1 output is -1, and unrealistic.
Question 2 Solution: There is no need to create a file code, create operating normally after file.

Question 3: The following compilation error occurs after exercise 10.3:

Question 3 Solution: The man 2 waitrequired header file, add operating normally find.

Attach practice run 5 results:

Fourth, code hosting

V. Other (perception, thinking, etc., optional)

This week the contents of system-level I / O, by this chapter I make my system based / O functions with understanding, which helps independent system functions, and so that I had at the time could not use the standard library functions accordingly solution.

Six, learning progress bar

	Blog amount (add / accumulate)	Learning time (add / accumulate)	Important growth
aims	30	400 hours
The third week	1/1	13/13
the fourth week	1/2	22/35
fifth week	1/3	30/65
Sixth Week	1/4	25/90
Week Seven	1/5	22/112
Eighth Week	1/6	25/137

Try recording "planned learning time" and "actual learning time" to the end see if you can improve their ability to plan. This study is very important work, is also useful. Consuming an estimated equation: Y = X + X / N, Y = XX / N, training more often, X, Y will close.

Reference: Why is estimated that software engineering software so hard , software engineering estimation method

• Plan study time: XX hours
• The actual study time: XX hours
• Improvements:
  (Available see more modern software engineering courseware software engineers the ability to self-evaluation form )

Reference material

• "In-depth understanding of computer systems V3" Study Guide