Sed - Revision history

Ardika Sulistija at 20:30, 3 October 2024

2024-10-03T20:30:46Z

← Older revision		Revision as of 20:30, 3 October 2024
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	* <b>/"ExtensionInstallAllowlist"</b>: \[/,/\],/: Searches between the start of the "ExtensionInstallAllowlist" list and the closing ],.		* <b>/"ExtensionInstallAllowlist"</b>: \[/,/\],/: Searches between the start of the "ExtensionInstallAllowlist" list and the closing ],.
	* <b>s/$\s*\],$/ "new_string",\n\1/</b>: Substitutes the closing ], with the new string followed by a newline and the original ],.		* <b>s/$\s*\],$/ "new_string",\n\1/</b>: Substitutes the closing ], with the new string followed by a newline and the original ],.
			** The <b>\1</b> is a "backreference" that refers to what was captured (or matched). In this case, the <b>\1</b> refers to the <b>(\s*\],\)</b> which is the closing bracket <b>],</b>. So it inserts the string\n before that.
	** <i>Adjust spaces to match the indentation.</i>		** <i>Adjust spaces to match the indentation.</i>
	* <b>your_file.json</b>: The file where the change will be made.		* <b>your_file.json</b>: The file where the change will be made.

Ardika Sulistija at 18:31, 3 October 2024

2024-10-03T18:31:06Z

← Older revision		Revision as of 18:31, 3 October 2024
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	* <b>-i</b>: Edits the file in place.		* <b>-i</b>: Edits the file in place.
	* <b>/"ExtensionInstallAllowlist"</b>: \[/,/\],/: Searches between the start of the "ExtensionInstallAllowlist" list and the closing ],.		* <b>/"ExtensionInstallAllowlist"</b>: \[/,/\],/: Searches between the start of the "ExtensionInstallAllowlist" list and the closing ],.
	* <b>s/$\s*\],$/ "new_string",\n\1/</b>: Substitutes the closing ], with the new string followed by a newline and the original ],. Adjust spaces to match the indentation.		* <b>s/$\s*\],$/ "new_string",\n\1/</b>: Substitutes the closing ], with the new string followed by a newline and the original ],.
			** <i>Adjust spaces to match the indentation.</i>
	* <b>your_file.json</b>: The file where the change will be made.		* <b>your_file.json</b>: The file where the change will be made.
	* Replace "new_string" with the actual string you want to add, and your_file.json with the path to your file.		* Replace "new_string" with the actual string you want to add, and your_file.json with the path to your file.

Ardika Sulistija at 18:29, 3 October 2024

2024-10-03T18:29:05Z

← Older revision		Revision as of 18:29, 3 October 2024
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	https://www.theunixschool.com/2014/08/sed-examples-remove-delete-chars-from-line-file.html		https://www.theunixschool.com/2014/08/sed-examples-remove-delete-chars-from-line-file.html

	=====How to target a specific String and insert a new string between some other character/string====		====How to target a specific String and insert a new string between some other character/string====
	----		----
	In this example, we will use the following list as an example:		In this example, we will use the following list as an example:

Ardika Sulistija at 18:28, 3 October 2024

2024-10-03T18:28:53Z

← Older revision		Revision as of 18:28, 3 October 2024
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	https://www.theunixschool.com/2014/08/sed-examples-remove-delete-chars-from-line-file.html		https://www.theunixschool.com/2014/08/sed-examples-remove-delete-chars-from-line-file.html

			=====How to target a specific String and insert a new string between some other character/string====
			----
			In this example, we will use the following list as an example:
			"Budapest": [
			"abc",
			"def",
			"ghi",

			],
			"ExtensionInstallAllowlist": [
			"abc",
			"def",
			"ghi",

			],

			So how can you insert a new string at the end of the "ExtensionInstallAllowlist" list, but before the "]," if there are multiple strings ( "ExtensionInstallAllowlist" vs "Budapest" ) to differentiate from?

			You can target the "ExtensionInstallAllowlist" list specifically and insert a new string before the ], using the following sed command:
			sed -i '/"ExtensionInstallAllowlist": \[/,/\],/s/$\s*\],$/ "new_string",\n\1/' your_file.json

			Explanation:
			* <b>-i</b>: Edits the file in place.
			* <b>/"ExtensionInstallAllowlist"</b>: \[/,/\],/: Searches between the start of the "ExtensionInstallAllowlist" list and the closing ],.
			* <b>s/$\s*\],$/ "new_string",\n\1/</b>: Substitutes the closing ], with the new string followed by a newline and the original ],. Adjust spaces to match the indentation.
			* <b>your_file.json</b>: The file where the change will be made.
			* Replace "new_string" with the actual string you want to add, and your_file.json with the path to your file.

Ardika Sulistija: Created page with "ADD NOTES: https://stackoverflow.com/questions/29399790/comment-out-lines-in-fstab-with-bash-script
https://www.bitdoze.com/sed-insert-append-text/#appending-text-with-sed You can use sed to print out specific lines of a file. I'm sure there's more you can do with sed but this is what I have for now. How to remove a line that contains a string like "aws-replication" from a file: # grep -i aws-replication test disk:x:6:aws-replication aws-replication:x:1001:..."

2024-09-11T14:27:13Z

Created page with "ADD NOTES: https://stackoverflow.com/questions/29399790/comment-out-lines-in-fstab-with-bash-script https://www.bitdoze.com/sed-insert-append-text/#appending-text-with-sed You can use sed to print out specific lines of a file. I'm sure there's more you can do with sed but this is what I have for now. How to remove a line that contains a string like "aws-replication" from a file: # grep -i aws-replication test disk:x:6:aws-replication aws-replication:x:1001:..."

New page

ADD NOTES: https://stackoverflow.com/questions/29399790/comment-out-lines-in-fstab-with-bash-script

https://www.bitdoze.com/sed-insert-append-text/#appending-text-with-sed

You can use sed to print out specific lines of a file. I'm sure there's more you can do with sed but this is what I have for now.

How to remove a line that contains a string like "aws-replication" from a file:
# grep -i aws-replication test
disk:x:6:aws-replication
aws-replication:x:1001:

# sed -i '/aws-replication/d' ./test
# grep -i aws-replication test
(no output as lines were deleted)

Usage
$ cat file
Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
Line 9
Line 10

To print one line (5)
$ sed -n 5p file
Line 5

To print multiple lines (5 & 8)
$ sed -n -e 5p -e 8p file
Line 5
Line 8

To print specific range (5 - 8)
$ sed -n 5,8p file
Line 5
Line 6
Line 7
Line 8

To print range with other specific line (5 - 8 & 10)
$ sed -n -e 5,8p -e 10p file
Line 5
Line 6
Line 7
Line 8
Line 10

To remove the last character in a file, and pipe the new output back to the file using tee:
$ sudo sed '$ s/.$//' /etc/cloud/cloud.cfg.d/99-datasource.cfg | tee /etc/cloud/cloud.cfg.d/99-datasource.cfg
'datasource_list': [
'Ec2',
'None'
]

To comment out a particular line or add something in front of a line:
$ cat testfile
1
2
3
4

$ sed -i '2 s/^/#/' testfile

$ cat testfile
1
#2
3
4

To comment out multiple lines (i.e. lines 2 through 4):
$ cat testfile
1
2
3
4

$ sed -i '2,4 s/^/#/' testfile

$ cat testfile
1
#2
#3
#4

$ sed '/AllowUsers/s/$/ centos2/' testfile
1
#2
#3
#4
AllowUsers ec2-user centos2

====How to replace words/characters in a file====
----
* "-i means to do an in-place edit. Without -i, then it doesn't make an actual edit but it will print the result. Use without -i for testing purposes is very helpful.
sed -i s/A/B/g means replace A with B:

# cat test.file
linux

# sed -i s,linux,linux_replaced,g test.file

# cat test.file
linux_replaced

------- Alternative:

# sed -i s/linux_replaced/linux/g test.file

# cat test.file
linux

=====How to replace strings with special characters=====
----
This replaces the string UUID=asfdsffd-a264-4fe2-84dc-33de230c4200 with /dev/mapper/vgroot-lvroot.
sed -i "s/UUID=asfdsffd-a264-4fe2-84dc-33de230c4200/\/dev\/mapper\/vgroot-lvroot/g" <file>

=====How to replace long strings with spaces=====
----
# cat test.file
linux /vmlinuz-3.10.0-1160.21.1.el7.x86_64 root=/dev/mapper/vglocal00-root00 ro crashkernel=auto biosdevname=1 modprobe.blacklist=mpt3sas net.ifnames=0 nomodeset rdblacklist=bfa,lpfc consoleblank=0 LANG=en_US.UTF-8 console=ttyS0 rd_NO_LVMCONF rd.lvm.conf=0

# sed "s:crashkernel=auto biosdevname=1 modprobe.blacklist=mpt3sas net.ifnames=0 nomodeset rdblacklist=bfa,lpfc consoleblank=0 LANG=en_US.UTF-8 ::g" test.file
linux /vmlinuz-3.10.0-1160.21.1.el7.x86_64 root=/dev/mapper/vglocal00-root00 ro console=ttyS0 rd_NO_LVMCONF rd.lvm.conf=0

----- or with -i ------

# sed -i "s:crashkernel=auto biosdevname=1 modprobe.blacklist=mpt3sas net.ifnames=0 nomodeset rdblacklist=bfa,lpfc consoleblank=0 LANG=en_US.UTF-8 ::g" test.file

# cat test.file
linux /vmlinuz-3.10.0-1160.21.1.el7.x86_64 root=/dev/mapper/vglocal00-root00 ro console=ttyS0 rd_NO_LVMCONF rd.lvm.conf=0

References: https://unix.stackexchange.com/questions/288521/with-the-linux-cat-command-how-do-i-show-only-certain-lines-by-number

=====How to add a character at the beginning of a line that contains a specific string=====
----
This will add a '#' at the beginning of the lines that contain the string 'asfdsffd-a264-4fe2-84dc-33de230c4200'.
sed -i '/asfdsffd-a264-4fe2-84dc-33de230c4200/ s/^/#/' ./etc/fstab

=====How to "append"/replace a string after finding a match=====
----

Template:
sed -i '/<find_line_that_matches_this_string/ s/<string_to_replace>/<replacement_string>/g' <file>
sed -i '/X/ s/Y/Z/g' <file>
* Find line that has X. Then replace Y with Z in that line.

This will find the line with "zzzsdfsf-a264-4fe2-84dc-123213124131", and replace "defaults" with "defaults,x-systemd.device-timeout=300":
$ cat fstab
UUID=77777f7f-b4f4-4ee4-b03f-c07c3f6f9act / xfs defaults 0 0
UUID=fdsa1389-b288-4175-ba95-fdsa43fdsf23 /boot xfs defaults 0 0
UUID=abcdefgf-5022-1212-8cae-32424324fds3 /var xfs defaults 0 0
UUID=zzzzzzzz-27ff-4732-8a24-8a2432434324 swap swap defaults 0 0
UUID=zzzsdfsf-a264-4fe2-84dc-123213124131 /test xfs defaults 0 0

$ sed '/zzzsdfsf-a264-4fe2-84dc-123213124131/ s/defaults/defaults,x-systemd.device-timeout=300/g' fstab
UUID=77777f7f-b4f4-4ee4-b03f-c07c3f6f9act / xfs defaults 0 0
UUID=fdsa1389-b288-4175-ba95-fdsa43fdsf23 /boot xfs defaults 0 0
UUID=abcdefgf-5022-1212-8cae-32424324fds3 /var xfs defaults 0 0
UUID=zzzzzzzz-27ff-4732-8a24-8a2432434324 swap swap defaults 0 0
UUID=zzzsdfsf-a264-4fe2-84dc-123213124131 /test xfs defaults,x-systemd.device-timeout=300 0 0

https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html

https://www.theunixschool.com/2014/08/sed-examples-remove-delete-chars-from-line-file.html

====sed: -e expression #1, char 193: unknown option to `s'====
----

If you get the error sed: -e expression #1, char 193: unknown option to `s', likely there is some syntax issue like a /. You would have to use \ delimiter like:
sed '/vmlinuz-/ s/something\/to\/replace/rd.lvm.vg=VG01/g' grub.cfg
* This replaces "something/to/replace" with rd.lvm.vg=VG01

* Another example. Trying to replace a string that has 'goodboy':
sed s,\'\goodboy\'\,,g <file>

* Another example if you are trying to replace a string with another string that has a ',' (use: \\,\\)
sed s,<string_to_replace>,\'hd0\\,\\gpt2\',g <file>