Have you ever wondered if there is a more convenient way to modify xml documents, beside libxml2? Sure, there is the nice dom within Firefox, but outside of that?
Well, there is augeas. AFAIK initially a project to standardize the interface to modify configuration files, in other words a common syntax for different formats.
Files are parsed trough so called lenses. Those lenses transform the actual file (e.g. httpd.conf or passwd) into a tree, which than can be modified by a set of augeas commands.
As lenses are bi-directional the same lense can be used to read a file, and to dump the (internal augeas) tree back into a valid configuration file. A nice concept, ey?
A back to the topic, one of the lenses - Xml.lns - can be used to modify XML files.
The following example creates a dummy xml file and modifies it using augtool.
$ sudo yum install augeas tidyp $ cat > abc.xml <<EOF <world poo="bar"> <child>Hi there.</child> </world> EOF $ augtool -LA -e <<EOF # Load XML lense set /augeas/load/xml/lens "Xml.lns" set /augeas/load/xml/incl "$PWD/abc.xml" load # Dump internal tree print /files # Add a note set /files/$PWD/abc.xml/world/note/#attribute/timestamp "now" set /files/$PWD/abc.xml/world/note/#text "Wtf" # Change the text of a node. set /files/$PWD/abc.xml/world/child/#text "Hello World." # Insert a new child after the present child ins child after /files/$PWD/abc.xml/world/child set /files/$PWD/abc.xml/world/child/#text "Hello Mars." # Insert a new child - anywhere .. set /files/$PWD/abc.xml/world/child/#text "Hello Jupiter Jones." # More children set /files/$PWD/abc.xml/world/child/child/child/#text "Hello Mars." print /files/$PWD/abc.xml save print /augeas//error EOF $ tidyp -xml -i -q < abc.xml $ unlink abc.xml
With the help from the people at #augeas on freenode, I found out that (a) there is a small bug preventing the usage of relative paths and (b) You need a little knowledge about the format you are writin to. In the (xml) example above, you need to specify attributes before specifying a #text node, because they are written first. If they were specified the other way round, augeas would fail while saving.