Using Multiple Utilities in Scripts and Accessing and Changing Previous Commands | CS 333, Study notes of Computer Science

Download Using Multiple Utilities in Scripts and Accessing and Changing Previous Commands | CS 333 and more Study notes Computer Science in PDF only on Docsity! 1 CS-344 - Unix Operating System Fundamentals Lecture 5 Using Multiple Utilities in Scripts and Accessing and Changing Previous Commands Based on slides created by Dr. Bangalore for the Spring 2005 offering of the course 9/15/2005 3 D e p a rt m e n t o f C o m p u te r a n d I n fo rm a ti o n S c ie n c e s U A B Shell Scripts (I)
Enables execution of complex tasks by using multiple commands in a single file
.bashrc or .bash_profile are such examples
Create simple script using any editor echo "Welcome" $USER echo "Today's date is: " date | cut -d' ' -f2-3 echo "You are logged in to: " hostname echo "There are" who | wc –l echo "user(s) currently logged in" echo "Your PATH is set to the following directories:" echo $PATH | tr ‘:’ ‘\n’ 2 9/15/2005 4 D e p a rt m e n t o f C o m p u te r a n d I n fo rm a ti o n S c ie n c e s U A B Shell Scripts (II)
To execute a script:  The script must have execute permission  File permissions can be set using “chmod”
or  Use source script_name 9/15/2005 5 D e p a rt m e n t o f C o m p u te r a n d I n fo rm a ti o n S c ie n c e s U A B Creating a complex script
Read a file – myfile.in
Output to the screen the total number of unique words
Output the list of unique words to the file words.out along with the number of times each word appears ordered with the most-used words listed first
Solution: tr -d '?."!:,;' < myfile.in | tr 'A-Z' 'a-z' | tr ' \t' '\n\n' \ | sed '/^$/d' \ | sort | uniq -c | sort -rn \ | tee words.out | wc -l 9/15/2005 6 D e p a rt m e n t o f C o m p u te r a n d I n fo rm a ti o n S c ie n c e s U A B Algorithm
Delete punctuation characters
Convert all characters to lowercase
Move each word to a separate line
Remove blank lines (if any)
Sort the lines
Remove duplicates
Compute word frequency and output to file
Compute the total number of unique words