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Sed
Sed is a very useful program that often is used as a filter in shell scripts.
From the sed man page:
Sed is a stream editor. A stream editor is used to perform basic text transformations on an input stream (a file or input from a pipeline).
Simple find-and-replace in text file
To replace all occurrences of the string findme and replace it with the string replcaceme in a file named test.file using sed just use the follwing command.
sed -e 's/findme/replaceme/g' test.fil > newtest.fil
Removing a complete XML element with body
Consider the following XML formated addressbook.
<?xml version="1.0" encoding="utf-8"?>
<addressbook>
<contact name="Bob">
<phone type="mobile" number="555 555 555" />
<address street="Lodge Hotell" city="Twin Peaks" />
</contact>
<contact name="Alice">
<phone type="work" number="555 555 555" />
<address street="Queen Street 3" city="Wonder Land" />
</contact>
</addressbook>
<addressbook>
<contact name="Bob">
<phone type="mobile" number="555 555 555" />
<address street="Lodge Hotell" city="Twin Peaks" />
</contact>
<contact name="Alice">
<phone type="work" number="555 555 555" />
<address street="Queen Street 3" city="Wonder Land" />
</contact>
</addressbook>
Lets say we want to remove Bob from this addressbook.
sed -e '/<contact name="Bob"/,/<\/contact>/ d' addressbook.xml