Changes between Version 10 and Version 11 of Csle2022/Agenda/linuxpackagemanagement

Timestamp:

Oct 19, 2022, 7:15:16 PM (2 years ago)

Author:

deepthi

Comment:

--

Csle2022/Agenda/linuxpackagemanagement

@@ -281 +281 @@
 ==== sed ====
 
+SED is a text stream editor used on Unix systems to edit files quickly and efficiently. The tool searches through, replaces, adds, and deletes lines in a text file without opening the file in a text editor. 
+
+- SED is a powerful text stream editor. Can do insertion, deletion, search and replace(substitution).
+- SED command in unix supports regular expression which allows it perform complex pattern matching.
+
+1.Replacing or substituting string : Sed command is mostly used to replace the text in a file. The below simple sed command replaces the word “unix” with “linux” in the file.
+
+`$sed 's/unix/linux/' geekfile.txt`
+
+2. Replacing the nth occurrence of a pattern in a line : Use the /1, /2 etc flags to replace the first, second occurrence of a pattern in a line. The below command replaces the second occurrence of the word “unix” with “linux” in a line.
+
+`$sed 's/unix/linux/2' geekfile.txt`
+
+3.Replacing all the occurrence of the pattern in a line : The substitute flag /g (global replacement) specifies the sed command to replace all the occurrences of the string in the line.
+
+`$sed 's/unix/linux/g' geekfile.txt`
+
+4.Replacing from nth occurrence to all occurrences in a line : Use the combination of /1, /2 etc and /g to replace all the patterns from the nth occurrence of a pattern in a line. The following sed command replaces the third, fourth, fifth… “unix” word with “linux” word in a line.
+
+`$sed 's/unix/linux/3g' geekfile.txt`
+
+5.Parenthesize first character of each word : This sed example prints the first character of every word in parenthesis.
+
+`$ echo "Welcome To The Geek Stuff" | sed 's/\(\b[A-Z]\)/\(\1\)/g'`
+
+6.Replacing string on a specific line number : You can restrict the sed command to replace the string on a specific line number. An example is
+
+`$sed '3 s/unix/linux/' geekfile.txt`
+
+7.Duplicating the replaced line with /p flag : The /p print flag prints the replaced line twice on the terminal. If a line does not have the search pattern and is not replaced, then the /p prints that line only once.
+
+`$sed 's/unix/linux/p' geekfile.txt`
+
+8.Printing only the replaced lines : Use the -n option along with the /p print flag to display only the replaced lines. Here the -n option suppresses the duplicate rows generated by the /p flag and prints the replaced lines only one time.
+
+`$sed -n 's/unix/linux/p' geekfile.txt`
+
+9.Replacing string on a range of lines : You can specify a range of line numbers to the sed command for replacing a string.
+
+`$sed '1,3 s/unix/linux/' geekfile.txt`
+
+10.Deleting lines from a particular file : SED command can also be used for deleting lines from a particular file. SED command is used for performing deletion operation without even opening the file
+Examples:
+ 1.To Delete a particular line say n in this example
+Syntax:
+`$ sed 'nd' filename.txt`
+
+Example:
+`$ sed '5d' filename.txt`
+
+2. To Delete a last line
+
+Syntax:
+
+`$ sed '$d' filename.txt`
+
+3. To Delete line from range x to y
+
+Syntax:
+
+`$ sed 'x,yd' filename.txt`
+
+Example:
+
+`$ sed '3,6d' filename.txt`
+
+4. To Delete from nth to last line
+
+Syntax:
+
+`$ sed 'nth,$d' filename.txt`
+
+Example:
+
+`$ sed '12,$d' filename.txt`
+
+5. To Delete pattern matching line
+
+Syntax:
+`$ sed '/pattern/d' filename.txt`
+
+Example:
+
+`$ sed '/abc/d' filename.txt`
+
+
+
 ==== awk ====