COP 3344-01 Introduction to Unix: Lecture 4

Learning objectives

After this class, you should be able to:

1. Use the following Unix commands: cmp, cut, diff , gunzip, gzip, head, sort, tail, tar, and wc.
2. Compare two (possibly binary) files to determine if they are different using cmp.
3. Find out how two files differ using diff.
4. Extract some text from each line of a file using cut.
5. Read the first few lines or last few lines of a file using head or tail respectively.
6. Sort a file using sort.
7. Count the number of words and lines in a file using wc.
8. Archive files using tar, and extract files from the archive.
9. Compress and uncompress files using gz.
10. Redirect standard input, standard output (including appending to a file), and standard error.
11. Combine commands using pipes.
12. Group commands using '(', ')', and ';'.

Reading assignment

1. JEA: Chapters 10-11, 23.9-23.14, Single Unix Specification for definitions of the commands.
2. Lecture slides: Lecture4.

Exercises and review questions

• Questions on current lecture's material
  1. Create a file called PracticeFile which contains three columns of text, separated by tabs.
  2. Output the first few lines and the last few lines of the file into another file, called file1, using features we have learned, such as I/O redirection. Next, output the contents of file1.
  3. Output only the second and third columns of the file PracticeFile using features we have learned.
  4. Output lines 4 to 8 of the file PracticeFile using pipes and commands we have learned (you may want to check documentation of some options to head and tail).
  5. Sort the contents of PracticeFile and output into a file called SortedPracticeFile.
  6. Check if the number of lines in PracticeFile and SortedPracticeFile are identical, using a command that we have learned.
  7. Check if the files PracticeFile and SortedPracticeFile are identical, using cmp.
  8. Modify the file PracticeFile by adding a few lines, changing a few lines, and deleting a few lines, and store it in a file called ModifiedPracticeFile. Use diff to find all the differences between the two files.
  9. Create a compressed archive of all the files you have created in this exercise, using tar and gzip. Move the compressed archive to a different directory, and extract the files. Check if you got the same files back. Check some of the files, against the originals, to ensure that the contents of the files have not changed.

• Questions on next lecture's material
  1. Write a simple shell script called info, which gives the date using the date command, and prints the current working directory.