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You must use your class account to do this homework. The attached sheet
contains the information needed for logging in. You will get the
sample files from the class account handout directory and you will
submit the homework electronically. You will type in answers to
questions in the text below, in a file.
Obtain this file by typing: getcopy sedHWanswers Whenever you see Question x. below, where x is an integer, put the answer in sedHWanswers. Start by putting your name and account id at the top of the file. |
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Type getcopy sample1.input This is a file with various statements about trees. Type more sample1.input to read it. Now type sed 's/tree/shoe horn/g' sample1.input As you can see, every occurrence of the word "tree" is replaced by the phrase "shoe horn." The contents of file sample1.input has not changed. In order to save the results, you could direct them to another file by typing, e.g. sed 's/tree/shoe horn/g' sample1.input > sample1.output |
Homework with sedQuestion 1. Now type sed 's/[s-t][a-h]./Judy/g' sample1.input Explain what happened and why. Why is only the first line affected? Don't forget to use your "Crib sheet" handed out in class. Put the answers in the homework file. Question 2. Now write a sed command that will substitute the word "button" for "tree", only if tree occurs at the end of a line (again use file sample1.input). Make sure to try it out! Put the sed command in the homework file. Question 3. Write a sed command that will substitute the word foible for the word tree but not the word trees. Can your sed command substitute foible for the occurrence of tree at the end of the first line? Why or why not? Again make sure to try it out! Answer the questions and put the sed command in the homework file. Question 4. Write a sed command that will replace two or more of the character e in a row with the string alala. Hint: use square brackets. The result should be: I think that I shall never salala a poem lovely as a tralala Binary tralalas have dual branches My family tralala is acyclic A tralala is not fralala |
Homework with grepGet a copy of sample2.input by typing:getcopy sample2.input This is a sample log file of the type generated by an http server whenever a client requests information or runs a cgi program. Type more sample2.input to take a look. Use grep or egrep in the following questions, again typing the answers into the file SedHWanswers. Make sure both sample1.input and sample2.input are in the same directory and that you are running your grep commands in that directory. Question 5. Type grep 'ee' *.input How many lines match and are printed? Which of the two files have lines that match? Question 6. Use grep to print the lines in the file sample2.input that contain "03." as part of the client hostname. There should only be 2 such lines. Since the character . is special and means any character, use \. when you want to match the actual period character specifically. Put the grep command in the homework file. Question 7. The log file (sample2.input) also contains the time at which the URL was sent to the server. Use grep to find lines for activity that occurred between 1 and 3 in the morning. Time is denoted as :hour:minute:second and each value between colons is two digits. Note: you can use square brackets in grep as well. There are again 2 such lines. Put the grep command in the homework file. Question 8. Use one grep command to find URLs from sample2.input that contain either .asp or .gif (there are 5) and put the grep command in the homework file. |
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For more information, check out the links on http://www.cs.smith.edu/~jfrankli/250f00/sed.html |
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Summary: due Thursday December 14 by midnight. Submit by typing submit sedHW sedHWanswers |