How to Delete string without opening a file

Shell Programming and Scripting
1

Hi Experts,

I have several big size file arround 900 MB. From the file I need to delete some common strings but without opening the file. here is example- in file

<?xml version='1.0' encoding='ISO-8859-1' standalone='no'?>
<LogItems>
<log logid="8423b5ae190810252359350480/1/1/1">

<category>ProcEngineBL.Normal</category>
<operation>DC::sendGetCommand</operation>
<starttime>20081025235935.515410</starttime>
<stoptime>20081025235935.723993</stoptime>
<status>FAILED</status>
</log>
<log logid="8423b5ae190810252359350480/1/1"><category>ProcEngineBL.Normal</category>
<operation>Get</operation>
<target>DC.Subscription</target>
<fullOperation>DC::getCommand</fullOperation>
<starttime>20081025235935.508385</starttime>
<stoptime>20081025235935.724373</stoptime>
<status>FAILED</status>
</log>
<log logid="8423b5ae136366384884759350480/1/1"><category>ProcEngineBL.Normal</category>
<operation>Get</operation>
<target>DC.Subscription</target>
<fullOperation>DC::getCommand</fullOperation>
<starttime>20081025235935.508385</starttime>
<stoptime>20081025235935.724373</stoptime>
<status>FAILED</status>

I want to delete the above Red Colored Strings from the File but without opeining the file. You know its 900MB file. so, its time consuming to open.

Please help.

2

If you want to modify a file you always have to open something (either using kernel's filesystem implementation or doing it the forensic way by opening a device directly and using the filesystem libs on user-space to control exactly what you're doing).

Anyway, the problem is not opening a file but reading it! And yet, I always have to read the file and then handle strings/patterns to delete something.

Hence,

 sed "/<\/log>/ { N; s/<\/log>\n<log logid=\"8423b5ae136366384884759350480\/1\/1\">//; s/<\/log>\n<log logid=\"8423b5ae190810252359350480\/1\/1\">// }" YOUR-900MB-FILENAME-HERE > new900MBfileWithoutThoseTwoEntries

This might take a while.

3

Cant we do something like this?
sed -n -e '/<log logid="8423b5ae190810252359350480/1/1">/d' file.txt > file.txt

4

no, you can't. You'd overwrite you input source while reading it.

5

Yeah, and furthermore this is a multi-line match.

6

man sed

.....
       -i[SUFFIX], --in-place[=SUFFIX]

              edit files in place (makes backup if extension supplied)
7 
sed '/<\/log>/{
N
s/<\/log>\n.*\/1\/1">//
}' filename