topic Re: sed-append question in Operating System - Linux

sed-append question

Gemini_2 — Mon, 25 Sep 2006 15:25:52 GMT

I have the following input

load /BC/TOC1
load /BC/TOC2

I want to add one more load after the last one, in this case: "load BC/TOC2"

sed "/^load/a\load /BC/TOC3" $file

it runs the sed twice :-( like the following
load /BC/TOC1
load /BC/TOC3
load /BC/TOC2
load /BC/TOC3

how do I change the sed statement to only append to the last one?

the desired output will be
load /BC/TOC1
load /BC/TOC2
load /BC/TOC3

thank you

Re: sed-append question

Abhijeet_3 — Mon, 25 Sep 2006 15:39:08 GMT

Alternative way is
echo " load/BC/TOC3" >> filename

Abhijeet

Re: sed-append question

Gemini_2 — Mon, 25 Sep 2006 15:42:06 GMT

it will not work because I have other stuff in the file. I just show you guys the portion of the file that I want to modify.

Re: sed-append question

James R. Ferguson — Mon, 25 Sep 2006 16:16:42 GMT

Hi Gemini:

Try:

# cat ./append
#!/usr/bin/sed -f
n
/^load TOC2/p
a\
load \/BC\/TOC3

...run as:

# ./append file

Regards!

...JRF...

Re: sed-append question

James R. Ferguson — Mon, 25 Sep 2006 17:03:24 GMT

Hi (again):

Sorry, that should look like:

# cat ./append
#!/usr/bin/sed -f

#!/usr/bin/sed -f
/^load \/BC\/TOC2/{
a\
load \/BC\/TOC3
}

...run as:

# ./append file

Regards!

...JRF...

Re: sed-append question

Gemini_2 — Mon, 25 Sep 2006 17:53:10 GMT

sorry, I am still not making myself clear.

the last entry may not always be /BC/TOC2, it can be /BC/TOC3, /BC/TOC4, the whole point is how to append the new entry just ONCE?

thank you

Re: sed-append question

James R. Ferguson — Mon, 25 Sep 2006 18:21:56 GMT

Hi Gemini:

# cat ./append
#!/usr/bin/sed -f
${
a\
load \/BC\/TOC_
}

# ./append file

...will append to the file's end.

Regards!

...JRF...

Re: sed-append question

Gemini_2 — Mon, 25 Sep 2006 19:17:43 GMT

are you sure?

is the difference between yours and mine the "_"? I still get the same result :-(

please help out...

Re: sed-append question

James R. Ferguson — Mon, 25 Sep 2006 19:29:53 GMT

Hi:

Well, mine works for me, so try this variation:

# #!/usr/bin/sed -nf
p
${
a\
load \/BC\/TOC_
}

...substitute anything you want for "TOC_".

Regards!

...JRF...

Re: sed-append question

Dennis Handly — Mon, 25 Sep 2006 19:39:30 GMT

I don't think you can use sed at all. Also, do you have more than one sequence of loads that can be present? If so, you can't even use awk unless you make a grep -n prepass:

#!/usr/bin/ksh
FILE=itrc_append

# fine last "load"
line=$(grep -n "^load" $FILE | tail -1 | sed 's/:.*$//')

# add one "load /BC/TOC3" after the last "load".
sed -e "${line}a\\
load /BC/TOC3" $FILE

Re: sed-append question

Gemini_2 — Mon, 25 Sep 2006 20:10:34 GMT

okay....

I should give a complete file to make my point clear

the file is like

----------------------
load /BC/TOC1
load /BC/TOC2

description: testing
vob: bc
---------------------

so, I can not just append at the end of the file..I need to append at the end of the load statement..

the solutions above are all at the end of the file.....

Re: sed-append question

Dennis Handly — Mon, 25 Sep 2006 20:36:05 GMT

>the solutions above are all at the end of the file.....

Mine is not. I find the LAST "load" and add after it.

Re: sed-append question

Sandman! — Mon, 25 Sep 2006 20:57:59 GMT

Try the sed command below. It inserts the line "load /BC/TOC3" right after the last load line in the input file.

sed '
/^load/,/^$/{
/^$/{i\
load /BC/TOC3
}
}' infile

~hope it helps

Re: sed-append question

Dennis Handly — Mon, 25 Sep 2006 21:25:29 GMT

Sandman's seems to work only if there is a blank line after the load. Mine works no matter how many blocks of "load"s or what follows them.

Re: sed-append question

Gemini_2 — Tue, 26 Sep 2006 19:26:54 GMT

Thanks for Dennis Handly's solution. that works very well.

I also like Sandman's solution, but I have question about your synatx

sed '
/^load/,/^$/{
/^$/{i\
load /BC/TOC3
}
}' infile

1.what does the first/second line mean?

I am confused at
/^load/,/^$/{
/^$/{i\

that is a new synatax to me..

please kindly shed some light..

Re: sed-append question

Dennis Handly — Tue, 26 Sep 2006 20:13:12 GMT

>1.what does the first/second line mean?

Basically for all lines from the first "load" to a blank line, do the {} block. Inside the block it tests to make sure it is on the blank line and if so, insert.

Re: sed-append question

Sandman! — Wed, 27 Sep 2006 01:20:35 GMT

My sed solution was based on the input file you had provided i.e

----------------------
load /BC/TOC1
load /BC/TOC2

description: testing
vob: bc
----------------------

>I am confused at
>/^load/,/^$/{
>/^$/{i\

...it's a nested sed construct which applies commands at a particular address which is within the selected block. So the above command grabs all lines that start with the word load (^load) upto the first blank line (^$). Once it reaches the blank line it inserts the desired line above the blank one.

hope it helps!