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Output of sed command to another sed command

 
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# 8  
Old 12-05-2013
Thank you bakunin for your comprehensive post. I will explore this option and hopefully create a cleaner solution

---------- Post updated at 12:37 PM ---------- Previous update was at 12:30 PM ----------

Quote:
Originally Posted by hergp
Hmm, it works here (without the -i option) on CentOS 6.4:
Code:
$ cat file1
head1
head2
head3
head4
$ cat file2
line1
line2
line3
$ sed '1i\'<(sed -n 1,2p file1) file2
head1
head2
line1
line2
line3

When I do the same I get the following

Code:
 
$ cat file1
head1
head2
head3
head4
$ cat file2
tail1
tail2
tail3
tail4
$ sed '1i\'<(sed -n 1,2p file1) file2
/dev/fd/63
tail1
tail2
tail3
tail4

Smilie
# 9  
Old 12-05-2013
Have you tried with the space, as RudiC suggested?

Code:
$ sed '1i\'<(sed -n 1,2p file1) file2
/dev/fd/63
tail1
tail2
tail3
tail4
$ sed '1i\' <(sed -n 1,2p file1) file2
head1
head2
tail1
tail2
tail3
tail4

(bash 4.2.24 on Debian)
# 10  
Old 12-05-2013
Quote:
Originally Posted by CarloM
Have you tried with the space, as RudiC suggested?

Code:
$ sed '1i\'<(sed -n 1,2p file1) file2
/dev/fd/63
tail1
tail2
tail3
tail4
$ sed '1i\' <(sed -n 1,2p file1) file2
head1
head2
tail1
tail2
tail3
tail4

(bash 4.2.24 on Debian)
Did try this also:

Code:
 
$ cat file1
head1
head2
head3
head4
$ cat file2
tail1
tail2
tail3
tail4
$ sed '1i\' <(sed -n 1,2p file1) file2
sed: couldn't write -1 items to stdout: Success
$ cat file2
tail1
tail2
tail3
tail4

# 11  
Old 12-05-2013
I dug into this a little bit more, and it seems, it depends on your shell, if you need a blank as RudiC suggested or not.

First with bash:
Code:
$ bash -c "sed '1i\' <(sed -n 1,2p file1) file2"
head1
head2
line1
line2
line3
$ bash -c "sed '1i\'<(sed -n 1,2p file1) file2"
/dev/fd/63
line1
line2
line3

Without the blank you get the line with /dev/fd/nnn as BigCroyd pointed out.

Whereas ksh does not seem to care
Code:
$ ksh -c "sed '1i\' <(sed -n 1,2p file1) file2"
head1
head2
line1
line2
line3
$ ksh -c "sed '1i\'<(sed -n 1,2p file1) file2"
head1
head2
line1
line2
line3

---------- Post updated at 14:22 ---------- Previous update was at 14:18 ----------

Quote:
Originally Posted by BigCroyd
Code:
$ sed '1i\' <(sed -n 1,2p file1) file2
sed: couldn't write -1 items to stdout: Success

... and another version... Smilie

This syntax does not seem to be very advisable with all these different outcomes. I withdraw my original example.
 
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