Shell Programming and Scripting

I want to replace a string by contents of file.

I am trying the following sed command:

Code:

cat sample | sed "s^<enter description here>^`cat details`^"

But it is not working.

Code:

a=`cat details`

and using $a will not help since it will affect the whitespaces.

What am I missing in the above sed command?

Hello anand_bh,

Following are the points for your posts.
1st: Kindly use code tags as per forum rules while using codes/commands/inputs in your posts. You can go through the link for forum rules as follows.
https://www.unix.com/misc.php?do=cfrules

2nd: There is no need of using cat file | sed .... here. As sed can read file by itself.

3rd: Following is an example for uses for sed command.
Let's say we have an example input file named test2 where we want to substitute a string named Control with chumma, then we can use as follows.

Code:

 sed 's#Control#chumma#g' test2

Output will be as follows.

Code:

chumma|AC-00011-CN-2475208 AC-00011-CN-2475211 AC-00007-CN-2475238 AC-00007-CN-2475241
chumma|AC-00011-CN-2475208 AC-00011-CN-2475211 AC-00007-CN-2475238 AC-00007-CN-2475241

4th: For more information on sed you can read manual page entry for it by man sed or you can go through n number of example by search utility option in this forum itself.

Hope this helps.


Thanks,
R. Singh

Thanks Ravinder for the reply.
Sorry for not following the code rule.

I will read the man page and update the result here if I found any.

Moderator's Comments:

@Ravinder: Yes, it is perfectly OK to remind people to read the man pages. This point can never be stressed enough. On the other hand, "read the man page" or "search the web" without even so much as a pointer what to search for is not all that much helpful. I might be naive, but many years of answering questions here still failed to make me jaded enough to suppose ill intentions every time. If someone writes a question i prima facie suppose s/he has already undergone some effort and came up blank - if only because s/he lacked the correct keywords to search for. Many thanks for your consideration.

You might want to concentrate on the "r" subcommand, which takes a file argument.

It will not be easy to directly replace a part of a line by the content of a file. To it seems like this is one of the very few occasions where you need to pipe the output of one sed into another. Consider the following:

inputfile:

Code:

===== line 1 =====
===== line 2 =====

replacementfile:

Code:

this
will
go
in

Script:

Code:

sed '1 r replacementfile'

Result:

Code:

===== line 1 =====
this
will
go
in
===== line 2 =====

The "r" subcommand takes a file parameter and places the contents of this file into the output stream. Notice, that this is NOT a replacement! The content of the file does NOT land on the pattern space and therefore you cannot further manipulate the result.

This is why i said you might need two seds, piping the output of the first (where the file content insertion takes place) into the other (where further manipulation might take place.

I hope this helps.

bakunin

Actually, when I use the sed given in post#1, it works perfectly for me as is. What exactly goes wrong? Please post sample and details files!

Yes it works.

Code:

 cat details
abc
 cat sample
some text
hello <enter description here> world
other text
 read a < details
 sed "s^<enter description here>^$a^" sample
some text
hello abc world
other text

q.e.d.