I have a config file as hive-site.xml
One configuration element is;
<property>
<name>hadoop.embedded.local.mode</name>
<value>true</value>
</property>
I want to change the "true" to "false" by a shell script. But in the file there are lots of configuration elements such as;
<value>true</value>
tags.
So the "sed" command I used to find and replace strings is difficult to be used here with my knowledge. Appreciate if anyone can help me with this.
This is probably a job for XPath and a reasonable XML library. Doing this from a shell script directly is going to create a complicated and likely fragile solution. I'm going to use python and the popular lxml library as an example:
from lxml import etree
tree = etree.fromstring('''
<property>
<name>hadoop.embedded.local.mode</name>
<value>true</value>
</property>
''')
e = tree.xpath('//property[name="hadoop.embedded.local.mode"]/value')[0]
e.text = 'false'
print etree.tostring(tree)
Basically that selects any property node (anywhere in the doc) if it contains a <name> element with that value, then it selects the value element. You can then modify the element's content to your liking and print as a string again. XPath is standard, so roughly the same code ought to work in other implementations as well.
Obviously quite a few ways to do this, but why not try awk (gawk)?
#!/bin/bash
gawk \
'
BEGIN {
FLAG = 0;
}
/hadoop.embedded.local.mode/ {
FLAG = 1;
}
/>[ ]*true[ ]*</ {
if (FLAG == 1) {
FLAG = 0
gsub("true", "false")
}
}
{
print
}
' "$@"
Invoke the above script as:
<script> hive-site.xml
You can give the whole block and change.
sed -i '/s/<property><name>hadoop.embedded.local.mode<\/name><value>true<\/value<\/property>
/<property><name>hadoop.embedded.local.mode<\/name><value>false<\/value><\/property>/'
hive-site.xml
If the value you want to change is always on the next line you can first get the line number of the desired element with
NUMBER=$(grep -n "<desired element>" filename | awk -F: '{print $1}')
Then increment to the next line
let NUMBER="NUMBER + 1"
Then use sed or ex to modify the value, I prefer ex in these cases, as it eliminates the need for an interim text file.
{
print "${NUMBER}s/true/false/"
print "wq"
} | ex filename
sed javax.jdo.option.ConnectionURL
new_val="Chandu_jdbc" sudo sed -i "/javax.jdo.option.ConnectionURL/!b;n;c${new_val}" /tmp/hive-site.xml sudo sed -i '/javax.jdo.option.ConnectionURL/!b;n;c'${new_val}' /tmp/hive-site.xml sudo sed -i "/javax.jdo.option.ConnectionURL/!b;n;c${new_val}" /tmp/hive-site.xml sudo sed -i '/javax.jdo.option.ConnectionURL/!b;n;c'"${new_val}"'' /tmp/hive-site.xml
