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RegExp: From first occurrance to last (at line start)

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# 1  
Old 01-07-2008
RegExp: From first occurrance to last (at line start)
So I have a log that contains something like this:
Quote:
preparing localhost0...
[some number of lines of junk]
localhost0: ls /
bin boot dev etc home lib lib64 lost+found misc mnt net opt proc root sbin selinux srv sys tmp tools usr var
localhost0: exit
[some number of lines of junk]
What I want is to get the first occurrence of "^localhost0" (at line start) and then everything else up to the last occurrence of "^localhost0" (at line start)

Ideally I don't even care about the 2 "localhost0" lines either. All I really care about is the information stored between the command and the exit call.

I cannot seem to think of a way to do this with grep... aka

Quote:
Grab the first line starting with "localhost0", plus all lines that follow, stopping at the last occurrence of "localhost0" (that is at the start of a line) prior to file end.
Any help?
# 2  
Old 01-07-2008
I can think of two approaches:
Store the data to display in memory while you figure out what is 'in' and what's 'out'.
Run through the file a couple of times.

As I don't know how big the file is, we'll go with the multiple passes solution - it's ugly but it has a predictable memory footprint Smilie

Code:
#!/bin/sh
first=`egrep -n "^$1" $2 | cut -d ':' -f 1 | head -1`
last=`egrep -n "^$1" $2 | cut -d ':' -f 1 | tail -1`
head -$last $2 | tail +$first | egrep -v "^$1"

usage: scriptname.sh localhost0 filename.log
If you want to keep displaying the 'localhost0' lines too, just leave off the last egrep -v
# 3  
Old 01-07-2008
Code:
awk '/^localhost0/,/^localhost0: exit/' file

# 4  
Old 01-07-2008
Quote:
Originally Posted by shamrock
Code:
awk '/^localhost0/,/^localhost0: exit/' file

My awk's not the best but wouldn't that only print the lines between the first and second ^localhost0? Rather than the first and last?
# 5  
Old 01-07-2008
With localhost0 lines:
Code:
awk '/^localhost0/ { min = min ? min : NR ; max = NR }  min { line[NR] = $0 } END { for ( i = min ; i <= max ; i++ ) { print line[i]}}' file

without:
Code:
awk '/^localhost0/ { min = min ? min : NR ; max = NR }  min { line[NR] = $0 } END { for ( i = min + 1 ; i < max ; i++ ) { print line[i]}}' file

# 6  
Old 01-08-2008
Quote:
Originally Posted by Smiling Dragon
My awk's not the best but wouldn't that only print the lines between the first and second ^localhost0? Rather than the first and last?
It will print all lines between and including the lines that start with ^localhost0. Isn't that the desired output.? Smilie
# 7  
Old 01-08-2008
Quote:
Originally Posted by shamrock
It will print all lines between and including the lines that start with ^localhost0. Isn't that the desired output.? Smilie
Quote:
Originally Posted by jjinno
What I want is to get the first occurrence of "^localhost0" (at line start) and then everything else up to the last occurrence of "^localhost0"
Gotta be precise here Smilie
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