Sed substitution preserving leading white spaces

Question

I've been trying to write a sed command to substitute a single word on single line, preserving all the leading white spaces and words.

e.g. From:

<Attr name="x" value="yes"/>

To:

<Attr name="x" value="no"/>

I know that I could just rewrite the entire line but I'd prefer a more elegant way to do it. Thanks!

`sed` doesn't touch whitespace unless you tell it to. How did you try `sed` that didn't give you the correct result? — Shahbaz, Jan 15 '14 at 16:04

Lajos Veres · Answer 1 · 2014-01-15T16:12:50.897

4

I think without adding more specific requirement this simple solution should be fine:

sed 's/"yes"/"no"/'

edited Jan 15 '14 at 16:12

answered Jan 15 '14 at 15:27

Lajos Veres

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You might want to change it to `s/"yes"/"no"` or `s/\/no` so you wouldn't change anything else accidentally. – Shahbaz Jan 15 '14 at 16:04
Thank you very much for your answer! But I think this wouldn't be an effective solution, as (my fault I didn't explain it) the file contains multiple entries and your solution would change the entire file. – mr.G Jan 16 '14 at 10:05
You can add the target line number before the s. – Lajos Veres Jan 16 '14 at 10:15

score 1 · Accepted Answer · edited May 23 '17 at 12:21

1

You can't parse XML with regexes. Use an XML processing tool. To replace the value for Attr nodes where name is "x" and value is "yes" you can use a tool like xmlstarlet:

echo '<doc>
  <Attr name="x" value="yes"/>
  <Attr name="y" value="yes"/>
  <Attr name="x" value="maybe"/>
</doc>' |
xmlstarlet ed -u '//Attr[@name="x"][@value="yes"]/@value' -v "no"

<?xml version="1.0"?>
<doc>
  <Attr name="x" value="no"/>
  <Attr name="y" value="yes"/>
  <Attr name="x" value="maybe"/>
</doc>

edited May 23 '17 at 12:21

Community

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1

answered Jan 15 '14 at 16:22

glenn jackman

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I've not tried it yet, but it seems the best solution and the most flexible! Thank you very much!!! – mr.G Jan 16 '14 at 10:06

score 0 · Answer 3 · answered Jan 15 '14 at 15:49

0

Lajos' solution will rewrite many occurences of word in file - that's probably not what you want.

Following sed invocation will replace first occurence of "yes" to "no" inside file.xml only in line 3:

sed -i 3s/yes/no/ file.xml

answered Jan 15 '14 at 15:49

Patryk Obara

1,847
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Sed substitution preserving leading white spaces

3 Answers3