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how to export a pipe variable directly to shell command

Posted on 2014-09-05
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Last Modified: 2014-09-06
Hi
I am working on a project to grep/awk/sed a file and directly process a command between two expressions.

for instance if the file reads

XXXXXXXX YYYYY ZZZZZ
firstmatch
du -h /home  
secondmatch
AAAAA BBBBBBB CCCC

I can extract the information I need (du -h /home) but can not make it run directly in a shell

sed '1,/firstmatch/d;/secondmatch/,$d |

I just end up with
>
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Question by:KCITS
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9 Comments
 
LVL 85

Expert Comment

by:ozo
ID: 40307067
`sed '1,/firstmatch/d;/secondmatch/,$d'  file`
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LVL 1

Author Comment

by:KCITS
ID: 40307157
Hi ozo
Not sure what your suggestion is.
isn't the command 'file' just for determining a file type?

I can export the sed result to a file with
sed '1,/firstmatch/d;/secondmatch/,$d'  > /home/testfile.sh
and then run it, but I was hoping to just output and run a single command directly
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LVL 85

Expert Comment

by:ozo
ID: 40307165
file was meant to be the name of your file containing
XXXXXXXX YYYYY ZZZZZ
firstmatch
du -h /home  
secondmatch
AAAAA BBBBBBB CCCC


you can output to a file with > /home/testfile.sh
but where are you telling sed where to get the input from?
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LVL 48

Expert Comment

by:Tintin
ID: 40307167
sed '1,/firstmatch/d;/secondmatch/,$d' /path/to/your/file | xargs
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LVL 85

Assisted Solution

by:ozo
ozo earned 668 total points
ID: 40307172
doesn't xargs with no utility specified default to  | xargs echo

`sed '1,/firstmatch/d;/secondmatch/,$d'  /path/to/your/file`
or
$(sed '1,/firstmatch/d;/secondmatch/,$d'  /path/to/your/file)
should execute the command directly
0
 
LVL 48

Accepted Solution

by:
Tintin earned 668 total points
ID: 40307178
Ah yes, correct ozo.

Meant to write

sed '1,/firstmatch/d;/secondmatch/,$d'  /path/to/your/file | bash
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LVL 85

Expert Comment

by:ozo
ID: 40307193
That could be better than `` or $() if there are multiple commands between your expressions
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LVL 38

Assisted Solution

by:Gerwin Jansen, EE MVE
Gerwin Jansen, EE MVE earned 664 total points
ID: 40307759
You can also call it eplicitly like this, supposing your shell is bash:

bash -c "$(sed '1,/firstmatch/d;/secondmatch/,$d' /path/to/your/file)"
0
 
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Author Closing Comment

by:KCITS
ID: 40308283
Thanks Guys

sorry my typo in the above expressions I accidentally omitted my source file, it should have read  
sed '1,/firstmatch/d;/secondmatch/,$d'  /home/testfile.txt|

all accepted solutions worked well, I also experimented and tried the below as an alternative, it worked also.

sed '1,/firstmatch/d;/secondmatch/,$d'  /path/to/your/file | sh  

cheers
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