Exercises. Part 3

• The following command will invoke a program called Git to download some Python files. $ git clone https://github.com/uiuc-cse/rankine.git
  Execute this line and then go into the directory rankine and list its contents. These scripts are designed to input and output their data through streams. For instance, execute python grab_stations.py.

  • What is the output?
  • How can we capture this output as a file?
  • The programs are designed to work in series:
    grab_stations.py feeds data into grab_forecast.py
grab_forecast.py feeds data into plot_forecast.py.
    Write a single line command to effect this entire process.

Navigate to the data/pipes directory for the following exercises.

• If we run sort on the file numbers.txt, what is the output? If we run sort -n on the same input, what do we get instead? why -n has this effect.

• What is the difference between $ wc -l < mydata.dat and $ wc -l mydata.dat

• The command uniq removes adjacent duplicated lines from its input. For example, run the following commands:

$ cat salmon.txt
$ uniq salmon.txt

• Why do you think uniq only removes adjacent duplicated lines^*?
    _{*Hint: think about very large data sets.}
  
  

• Which other command could you combine with it in a pipe to remove all duplicated lines?

• Examine the file called animals.txt using less. What text passes through each of the pipes and the final redirect in the pipeline below?

$ cat animals.txt | head -5 | tail -3 | sort -r > final.txt

• The command:

$ cut -d, -f 2 animals.txt

produces the following output:

deer
rabbit
raccoon
rabbit
deer
fox
rabbit
bear

• What other command(s) could be added to this in a pipeline to find out what animals the file contains (without any duplicates in their names)?