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How to use sed to change file contents

Posted on 2009-05-18
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Last Modified: 2013-12-16
New to sed... I have the following statement that when entered on the command line works properly to make the desired replacement.  This version sends the result to stdout.  I can also redirect to a new file by appending ">newfile".  But I want to change the original file and when I redirect to the same file name I get an empty file.  What am I missing?  How do I change the original file?

sed '/^<script language=javascript><\!-- /,/^ -->/c<body>' sedtesttarget.html

Thanks.
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Question by:ttheimer
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3 Comments
 
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Accepted Solution

by:
ewest02 earned 250 total points
ID: 24415321
GNU sed has a --in-place (or -i) option to read/write the named file

Alternatively, you can use ed
The general approach is to use cat with a HERE directive to pass directives to ed

cat <<EOF | ed myfile
1,$s/some text/SOME TEXT/
.
w
q
EOF

In this example, open "myfile" and replace "some text" with "SOME TEXT".
The directives for ed overlap with those for sed -- they are related.

  --Eric
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Author Comment

by:ttheimer
ID: 24415484
The --in-place (or -i) option was not noted in my [paper] reference text - found it in the man file.  Works perfectly.  Thanks.

New command:

sed --in-place '/^<script language=javascript><\!-- /,/^ -->/c<body>' sedtesttarget.html
0
 

Author Comment

by:ttheimer
ID: 24415485
The --in-place (or -i) option was not noted in my [paper] reference text - found it in the man file.  Works perfectly.  Thanks.

New command:

sed --in-place '/^<script language=javascript><\!-- /,/^ -->/c<body>' sedtesttarget.html
0

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