Sed - Revision history

Jimbo: Reverted edits by Judy123 (Talk) to last revision by Jimbo

2010-06-28T13:14:50Z

Reverted edits by Judy123 (Talk) to last revision by Jimbo

Judy123 at 08:19, 28 June 2010

2010-06-28T08:19:54Z

Jimbo at 19:46, 28 May 2007

2007-05-28T19:46:24Z

Jimbo at 19:10, 28 May 2007

2007-05-28T19:10:56Z

65.9.151.238 at 22:22, 1 May 2006

2006-05-01T22:22:56Z

Jimbo: add mention of the -i argument

2006-02-24T20:44:28Z

add mention of the -i argument

Dave: more links and delimiter info

2005-10-03T14:21:23Z

Dave: example on global sed replacement

2004-12-23T22:34:11Z

example on global sed replacement

Dave at 16:44, 27 November 2004

2004-11-27T16:44:22Z

Dave at 16:42, 27 November 2004

2004-11-27T16:42:24Z

@@ Line 30: / Line 30: @@
 As you can see, no changes were made to the file itself - '''sed''' merely wrote the edited stream to standard output.  You can easily put the changed data in a new file with the help of [[redirection]]:
   dave@samizdata:~% '''sed s/dave/david/ sed_testfile > sed_testfile_new'''
   dave@samizdata:~% '''more sed_testfile_new'''

@@ Line 30: / Line 30: @@
 As you can see, no changes were made to the file itself - '''sed''' merely wrote the edited stream to standard output.  You can easily put the changed data in a new file with the help of [[redirection]]:
   dave@samizdata:~% '''sed s/dave/david/ sed_testfile > sed_testfile_new'''
   dave@samizdata:~% '''more sed_testfile_new'''

@@ Line 61: / Line 61: @@
 or as simple as
   > sed s%/dev/am0%/dev/gm0%g example.fstab > example.fstab.new
 For more info, check out these pages:

@@ Line 1: / Line 1: @@
-Short for "Streamline Editor", sed allows you to run a file through it and either match or change data without actually editing the file itself. This can be particularly handy if you need to make a lot of similar changes to a file -- e.g., you find out you consistently put in a wrong hostname in a configuration file, and you need to change your conf file to point to the right server....except the same change needs to be made 100 times. [[sed]] to the rescue.
+Short for "Stream Editor", '''sed''' allows you to run a stream (for example, the contents of a file, or the output of a program) through it and either match or change data. This can be particularly handy if you need to make a lot of similar changes to a file -- e.g., you find out you consistently put in a wrong hostname in a configuration file, and you need to change your conf file to point to the right server....except the same change needs to be made 100 times. [[sed]] to the rescue.
 Note that the change will only happen on the first instance of the phrase in each line.
@@ Line 28: / Line 28: @@
   dave@samizdata:~%
-As you can see, the changes were not actually made to the file. I didn't tell it to put the  changes anywhere! Easily fixed with the help of [[redirection]]:
+As you can see, no changes were made to the file itself - '''sed''' merely wrote the edited stream to standard output.  You can easily put the changed data in a new file with the help of [[redirection]]:
   dave@samizdata:~% '''sed s/dave/david/ sed_testfile > sed_testfile_new'''
@@ Line 50: / Line 50: @@
 Will give you a new_dhcpd.conf file with the changes made. You'll want to check the file by hand to make sure that the changes are correct, but you just saved yourself a lot of typing :)
-Another option for using sed is to have it make changes in place, but save the original version of the file(s) with a suffix (like .bak) added, using the -i argument.  For example:
+'''sed''' can also be used to make changes to a file or files directly, while backing up the original version of the file(s).  This is done using the -i argument, along with the desired suffix for backed up files.  For example:
   samizdata# '''sed -i .bak s/10.1.0./10.2.0./ dhcpd.conf'''
@@ Line 57: / Line 57: @@
   dhcpd.conf.bak
-Note that the standard delimiter is "/" but it can be just about anything; %, _, even commas. So changing a file with lots of forward-slashes (/) can be as ugly as
+Note that the standard delimiter is "/" but it can be just about anything; %, _, or even commas. So changing a file with lots of forward-slashes (/) can be as ugly as
   > sed s/\/dev\/am0/\/dev\/gm0/g example.fstab > example.fstab.new
 or as simple as

@@ Line 63: / Line 63: @@
 For more info, check out these pages:
 http://www.student.northpark.edu/pemente/sed/
 http://www.faqs.org/faqs/editor-faq/sed/
 http://www.grymoire.com/Unix/Sed.html
 [[Category:System Commands]]

@@ Line 5: / Line 5: @@
 The most common usage is to change all instances of a phrase to another; to wit:
-  dave@samizdata:~% cat sed_testfile
+  dave@samizdata:~% '''cat sed_testfile'''
    dave
    dave
@@ Line 12: / Line 12: @@
    dave
    freebsd
-  dave@samizdata:~% sed s/dave/david/ sed_testfile
+  dave@samizdata:~% '''sed s/dave/david/ sed_testfile'''
    david
    david
@@ Line 19: / Line 19: @@
    david
    freebsd
-  dave@samizdata:~% more sed_testfile
+  dave@samizdata:~% '''more sed_testfile'''
    dave
    dave
@@ Line 30: / Line 30: @@
 As you can see, the changes were not actually made to the file. I didn't tell it to put the  changes anywhere! Easily fixed with the help of [[redirection]]:
-  dave@samizdata:~% sed s/dave/david/ sed_testfile > sed_testfile_new
+  dave@samizdata:~% '''sed s/dave/david/ sed_testfile > sed_testfile_new'''
-  dave@samizdata:~% more sed_testfile_new
+  dave@samizdata:~% '''more sed_testfile_new'''
    david
    david
@@ Line 46: / Line 46: @@
 To give you another example of how useful [[sed]] can be, let's say that you have a DHCP server and want to change a whole segment's range:
-  samizdata# sed s/10.1.0./10.2.0./ dhcpd.conf > new_dhcpd.conf
+  samizdata# '''sed s/10.1.0./10.2.0./ dhcpd.conf > new_dhcpd.conf'''
 Will give you a new_dhcpd.conf file with the changes made. You'll want to check the file by hand to make sure that the changes are correct, but you just saved yourself a lot of typing :)
 Note that the standard delimiter is "/" but it can be just about anything; %, _, even commas. So changing a file with lots of forward-slashes (/) can be as ugly as

@@ Line 40: / Line 40: @@
   dave@samizdata:~%
-You'll also note that it only changed the first instance of the word per line; to change all instances on each line, you'll want to use the "g" modifier (to make '''global''' switches). See the man page for more details.
+You'll also note that it only changed the first instance of the word per line; to change all instances on each line, you'll want to use the "g" modifier (to make '''global''' switches) like this:
 To give you another example of how useful [[sed]] can be, let's say that you have a DHCP server and want to change a whole segment's range:

← Older revision		Revision as of 16:44, 27 November 2004
Line 40:		Line 40:
	dave@samizdata:~%		dave@samizdata:~%

		+	You'll also note that it only changed the first instance of the word per line; to change all instances on each line, you'll want to use the "g" modifier (to make '''global''' switches). See the man page for more details.

	To give you another example of how useful [[sed]] can be, let's say that you have a DHCP server and want to change a whole segment's range:		To give you another example of how useful [[sed]] can be, let's say that you have a DHCP server and want to change a whole segment's range:

← Older revision		Revision as of 16:42, 27 November 2004
Line 46:		Line 46:

	Will give you a new_dhcpd.conf file with the changes made. You'll want to check the file by hand to make sure that the changes are correct, but you just saved yourself a lot of typing :)		Will give you a new_dhcpd.conf file with the changes made. You'll want to check the file by hand to make sure that the changes are correct, but you just saved yourself a lot of typing :)
		+
		+	For more info, check out this page: http://www.student.northpark.edu/pemente/sed/

	[[Category:System Commands]]		[[Category:System Commands]]