sed h and g options - Shell Programming and Scripting

sivasenthil_k · #1 01-04-2006

Hi ..

Happy New Year..

If i do a

sed -e '
/BEGIN/,/END/{
h
/xxx/{
g
p
}
}
' temp1

I have two queries in this script

1.Will the block between BEGIN and END be stored in the hold buffer before executing the /xxx/ ..

2.When will /xxx/ be executed ..( Is it after one full block between BEGIN and END is completed ?)

temp1 looks like

BEGIN
sdfdsf
sdfsdf
xxx
END
BEGIN
sdfdsf
sdfsdf
END

Thanks..Siva

zazzybob · #2 01-04-2006

Have you tested it yourself?

Cheers
ZB

sivasenthil_k · #3 01-04-2006

Yes I tested it myself ..

My objective is to take the block which has only xxx in it

But it gives output like

BEGIN
sdfdsf
sdfsdf
xxx
xxx
END
BEGIN
sdfdsf
sdfsdf
END

.. I am pretty new to sed .. may be my script has some basic error .. please help

vino · #4 01-04-2006

This looks fine.. It makes use sed's advanced flow control commands

Code:

[/tmp]$ cat 1
BEGIN
sdfdsf
sdfsdf
xxx
END
BEGIN
sdfdsf
sdfsdf
END
[/tmp]$ sed -n -e '/BEGIN/{
:top
N
/END/b end
b top
:end
s_.*xxx.*_&_p
}' 1
BEGIN
sdfdsf
sdfsdf
xxx
END
[/tmp]$

Yet another similiar sed solution

Code:

sed -n -e '/BEGIN/{
:top
/END/!{
N;        
b top
}    
s_.*xxx.*_&_p
}' 1

Cheers'
Vino

sivasenthil_k · #5 01-04-2006

Thanks Vino

It works ..

But what if I need the block with two patterns in it ..( the order of occurence of the pattern is not known ..

Could you help me do this using hold and get options in sed ..
I am a beginner in sed and I would love to learn using h and g options ..
( as I had asked in my original question .. /BEGIN,/END/h .. will the block be stored in hold space ??)

Thanks
Siva

vino · #6 01-04-2006

Quote:

Originally Posted by sivasenthil_k

But what if I need the block with two patterns in it ..( the order of occurence of the pattern is not known ..

Give me an example.

Quote:

Originally Posted by sivasenthil_k

( as I had asked in my original question .. /BEGIN,/END/h .. will the block be stored in hold space ??)

Sed works as follows: Pick up a line. Do the specified operations on that. Read the next line. Do the specified operations... etc.. So, in your case, the first line with /BEGIN/ will be in the hold space.

sivasenthil_k · #7 01-04-2006

Hi Vino

Thanks for the reply

Example is ..

Say I need the blocks with xxx and yyy in the file below ( I need the first and last blocks to be in the output .. which has xxx and yyy )

BEGIN
aaa
yyy
bbb
ccc
xxx
END
BEGIN
aaa
yyy
bbb
ccc
END
BEGIN
aaa
xxx
bbb
ccc
END
BEGIN
aaa
xxx
bbb
ccc
yyy
END

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