Working with Unix

Self-Help

Exercise 5

1. Use man to look up the flag for human-readable output from ls.

2. Get help with man by typing man man into the console.

3. Wouldn’t it be nice if there was a calendar command? Use apropos to look for such a command, then use man to read about how that command works.

Solution to Exercise 5

1. -h. Human readable output output outputs the file size using MB, GB instead of bytes

2. useful: cal -3

Get Wild

Exercise 6

1. Before I organized the photos by year, what command would have listed all of the photos of type .png?

2. Before I organized the photos by year, what command would have deleted all of my hiking photos?

3. What series of commands would you use in order to put my figures for a data science course and the pictures I took in the lab into their own folders?

Solution to Exercise 6

1. ls *.png

2. rm *-hiking*.jpg

3. mkdir data-science-course
   mkdir lab-pictures
   mv figure-*.svg data-science-course
   mv lab*.jpg lab-pictures
   

Search

Exercise 7

1. Search states.txt and canada.txt for lines that contain the word “New”.

2. Make five text files containing the names of states that don’t contain one of each of the five vowels.

3. Download the GitHub repository for this book and find out how many .html files it contains.

Solution to Exercise 7

Download required files:

curl https://seankross.com/notes/states.txt -O
curl https://seankross.com/notes/canada.txt -O

1. grep New states.txt canada.txt
   

2. grep -iv 'a' states.txt > states-without-a.txt
   grep -iv 'e' states.txt > states-without-e.txt
   grep -iv 'i' states.txt > states-without-i.txt
   grep -iv 'o' states.txt > states-without-o.txt
   grep -iv 'u' states.txt > states-without-u.txt
   

   compacter:

   for vowel in a e i o u; do grep -iv $vowel states.txt > states-without-$vowel.txt; done
   

3. git clone https://github.com/seankross/the-unix-workbench
   find the-unix-workbench -iname '*.html' | wc -l
   

Pipes

Exercise 8

1. Use pipes to figure out how many US states contain the word “New.”

2. Examine your ~/.bash_history to try to figure out how many unique commands you’ve ever used. (You may need to look up how to use the uniq and sort commands).

Solution to Exercise 8

1. grep New states.txt canada.txt | wc -l
   

2. Note that uniq only removes subsequent repeated lines. If the line is separated with a different line, then uniq does not remove the duplicate.

   The same behavior can also be achieved using sort -u without using uniq

   sort ~/.histfile | uniq