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-   -   shell mini cd manager question (http://p2p.wrox.com/book-beginning-linux-programming-4th-edition-isbn-978-0-470-14762-7/94240-shell-mini-cd-manager-question.html)

mashour06 March 8th, 2015 12:03 PM

shell mini cd manager question
 
Hello,
chapter 2 mini CD manager. Can any one please explain the next code:
in the function remove_records():
[code]

grep -v "^${cdcatnum}," $title_file > $temp_file
mv $temp_file $title_file
grep -v "^${cdcatnum}," $tracks_file > $temp_file
mv $temp_file $tracks_file

[code]
any help will be greatly appreciated.
thank you.

geodoomgr June 16th, 2018 04:11 PM

what does the grep do
 
the code finds lines in the file named title_file
Actually the code finds the lines that do NOT begin with the specified pattern
and saves all these lines in a temporary file. Then the next line renames the temporary file
and gives it the name of the existing file, so it actually substitutes the existing file with a file that does not have the specific lines , so in other words the specific lines were removed.


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