RHEL7 Sed Command Examples

Sed Command in Unix and Linux Examples

                                   

 

Sed is a Stream Editor used for modifying the files in unix (or linux). Whenever you want to make changes to the file automatically, sed comes in handy to do this. Most people never learn its power; they just simply use sed to replace text. You can do many things apart from replacing text with sed. Here I will describe the features of sed with examples.

 

Linux Sed Commands	Linux Sed Command Description
sed 's/Nick/John/g' report.txt	Replace every occurrence of Nick with John in report.txt
sed 's/Nick|nick/John/g' report.txt	Replace every occurrence of Nick or nick with John
sed 's/Nick/John/2' report.txt	Command Replaces the second occurrence of the word "Nick" with "John" in a line.
sed 's/Nick/John/3g' report.txt	Replacing from nth occurrence to all occurrences in a line,In This example 3rd ,4rth,5th …..
sed '3 s/unix/linux/' file.txt	Replacing string on a specific line number.
sed '/unix/ a "Add a new line"' file.txt	The sed command can add a new line after a pattern match is found. The "a" command to sed tells it to add a new line after a match is found
sed '/unix/ i "Add a new line"' file.txt	The sed command can add a new line before a pattern match is found. The "i" command to sed tells it to add a new line before a match is found.
sed '/unix/ c "Change line"' file.txt	The sed command can be used to replace an entire line with a new line. The "c" command to sed tells it to change the line.
sed 's/^/ /' file.txt >file_new.txt	Add 8 spaces to the left of a text for pretty printing
sed -n '/Of course/,/attention you \ pay/p' myfile.	Display only one paragraph, starting with "Of course" and ending in "attention you pay"
sed -n 12,18p file.txt	Show only lines 12-18 of file.txt
sed 12,18d file.txt	Show all of file.txt except for lines from 12 to 18
sed -n -e '5,7p' -e '10,13p' myfile.txt	Display lines 5-7 and 10-13 from myfile.txt:
sed -f script.sed file.txt	Write all commands in script.sed and execute them
sed '$d' file.txt	Delete the last line
sed '/[0-9]\{3\}/p' file.txt	Print only lines with three consecutive digits
sed '17,/disk/d' file.txt	Delete all lines from line 17 to 'disk'
sed 's/^[ ^t]*//' file.txt	Delete all spaces in front of every line of file.txt
sed 's/[ ^t]*$//' file.txt	Delete all spaces at the end of every line of file.txt
sed 's/^[ ^t]*//;s/[ ^]*$//' file.txt	Delete all spaces in front and at the end of every line of file.txt
ip route show | sed 's/  */ /g'	To replace multiple blank spaces with a single space, we will use the output of ip route show and a pipeline
sed 's/foo/bar/' file.txt	Replace foo with bar only for the first instance in a line
sed 's/foo/bar/4' file.txt	Replace foo with bar only for the 4th instance in a line.
sed 's/foo/bar/g' file.txt	Replace foo with bar for all instances in a line.
sed '30,40 s/version/story/g' myfile.txt	Replacing words only within a line range (30 through 40, for example)
sed '/baz/s/foo/bar/g' file.txt	Only if line contains baz, substitute foo with bar
sed -n '/^Jul  1/ p' /var/log/secure	Viewing the authorization and authentication activities that took place on July 2, as per the /var/log/secure log in a CentOS 7 server
sed '/^#\|^$\| *#/d' httpd.conf	To remove empty lines or those beginning with # from the Apache configuration file,
sed '/./,/^$/!d' file.txt	Delete all consecutive blank lines except for EOF
sed '/^$/N;/\n$/D' file.txt	Delete all consecutive blank lines, but allows only top blank line
sed '/./,$!d' file.txt	Delete all leading blank lines
sed -e :a -e '/^\n*$/{$d;N;};/\n$/ba' \ file.txt	Delete all trailing blank lines
sed '1,20 s/Johnson/White/g' file.txt	Do replacement of Johnson with White only on lines between 1 and 20
sed '1,20 !s/Johnson/White/g' file.txt	Do replacement of Johnson with White (match all except lines 1-20)
sed -i'.orig' 's/this/that/gi' myfile.txt	suffix following the -i option (inside single quotes) to be used to rename the original file.   Replace all instances of this or This (ignoring case) with that in myfile.txt, and we will save the original file as myfile.txt.orig.
sed -i 's/that/this/gi;s/line/verse/gi' myfile.txt	Performing two or more substitutions at once
sed 's/unix/linux/p' file.txt	The /p print flag prints the replaced line twice on the terminal. If a line does not have the search pattern and is not replaced, then the /p prints that line only once.
sed -n 's/unix/linux/p' file.txt	Use the -n option along with the /p print flag to display only the replaced lines. Here the -n option suppresses the duplicate rows generated by the /p flag and prints the replaced lines only one time
sed '/./{H;$!d;};x;/regex/!d' file.txt	Print paragraphs only if they contain regex
sed -e '/./{H;$!d;}' -e 'x;/RE1/!d;\ /RE2/!d;/RE3/!d' file.txt	Print paragraphs only if they contain RE1, RE2 and RE3
sed 's/\(.*\)foo/bar/' file.txt	Replace only the last match of foo with bar
sed '/regexp/!d' file.txt	grep equivalent
sed -n '/regexp/{g;1!p;};h' file.txt	Print the line before the one matching regexp, but not the one containing the regexp
sed -n '/regexp/{n;p;}' file.txt	Print the line after the one matching the regexp, but not the one containing the regexp
sed '/pattern/d' file.txt	Delete lines matching pattern
sed '/./!d' file.txt	Delete all blank lines from a file
sed '/^$/N;/\n$/N;//D' file.txt	Delete all consecutive blank lines except for the first two
sed -n '/^$/{p;h;};/./{x;/./p;}'\ file.txt	Delete the last line of each paragraph
sed 's@/usr/bin@&/local@g' path.txt	Replace /usr/bin with /usr/bin/local in path.txt
sed -e '/^#/d' /etc/services | more	View the services file without the commented lines
sed '/regex/{x;p;x;G;}' file.txt	Insert blank line above and below
sed 's/^[ ^t]*//' file.txt	Delete all spaces in front of every line of file.txt
sed 's/[ ^t]*$//' file.txt	Delete all spaces at the end of every line of file.txt
sed 's/^[ ^t]*//;s/[ ^]*$//' file.txt	Delete all spaces in front and at the end of every line of file.txt
sed 's/unix/linux/' file.txt| sed 's/os/system/'	Sed provides -e option to run multiple sed commands in a single sed command. The above output can be achieved in a single sed command as shown below.
sed -e 's/#.*//;/^$/d'  thegeekstuff.txt	Eliminate Comments and Empty Lines Using sed
sed -i '1d' /tmp/passwd	Editing the Source file by using ‘-i’ option. Above command will delete the first line of source file /tmp/passwd
root@nextstep4it:~# sed -i.bak '1d' /tmp/passwd root@nextstep4it:~# ls -l /tmp/passwd* -rw-r--r-- 1 root root 2229 Nov 24 22:36 /tmp/passwd -rw-r--r-- 1 root root 2261 Nov 24 22:35 /tmp/passwd.bak	In the above sed command , 1st line of file /tmp/passwd will be deleted but before that sed command takes the backup of /tmp/passwd as /tmp/passwd.bak
$ sed -n 's/Linux/Linux-Unix/gpw output' thegeekstuff.txt 1. Linux-Unix Sysadmin, Linux-Unix Scripting etc. 4. Storage in Linux-Unix $ cat output 1. Linux-Unix Sysadmin, Linux-Unix Scripting etc. 4. Storage in Linux-Unix	Write Changes to a File and Print the Changes Using sed s//gpw
ip route show |sed -n '/src/p' | sed -e 's/  *//g'| cut -d ' '-f9	Combining sed and other commands   extract our IP address from the output of the ip route command. We will begin by printing only the line where the word src is. Then we will convert multiple spaces into a single one. Finally, we will cut the 9th field (considering a single space as field separator), which is where the IP address is: