Sed inside a while read loop - sed

Question

I have been reading a lot of questions and answers about using sed within a while loop. I think I have the command down correctly, but I seem to get no output once I put all of the pieces together. Can someone tell me what I am missing?
I have an input file with 700 variables, one on each line. I need to use each of these 700 variables within a sed command. I run the following command to verify variables are outputting correctly:
cat Input_File.txt | while read var; do echo $var; done
I then try to add in the sed command as follows:
cat Input_File.txt | while read var; do sed -n "/$var/,+10p" Multi-BLAST_5814.txt >> Multi_BLAST_Subset; done
This command leaves me without an error, but a blinking cursor as if this is an infinite loop. It should use each of the 700 variables, find the corresponding line in Multi_BLAST_5814.txt and output the search variable line and the 10 lines after the search term into a new file, appending each as it goes. I can execute the sed command alone with a manually set single value variable successfully and I can execute the while loop successfully using the input file. Anyone have a thought as to why this is not working?
User, that is exactly what I have done to this point.
I have a large text file (128 MB) with BLAST output. I need to search through this for a subset of results for 769 samples (Out of the 5814 samples that are in the file).
I have created a .txt file with those 769 sample names.
To test grep and sed, I manually assigned a variable with one of the 769 samples names I need to search and can get the results I need as follows:
$ Otu="S41_Folmer_Otu96;size=12;"
$ grep $Otu -A 10 Multi_BLAST_5814.txt
OR
$ sed -n "/$Otu/,+10p" Multi_BLAST_5814.txt
The OUTPUT is exactly what I want as follows:
Query= S41_Folmer_Otu96;size=12;
Length=101
Sequences producing significant alignments: Score(Bits) E Value
gi|58397553|gb|AY830431.1| Scopelocheirus schellenbergi clone... 180 1E-41
gi|306447543|gb|HQ018876.1| Liposcelis paeta isolate CZ cytoc... 174 6E-40
gi|306447533|gb|HQ018871.1| Liposcelis decolor isolate CQ cyt... 104 9E-19
gi|1043259532|gb|KX130860.1| Batocera rufomaculata isolate Br... 99 4E-17
gi|987210821|gb|KR141076.1| Psocoptera sp. BOLD:ACO1391 vouch... 81 1E-11
To Test to make sure the input file contains the correct variables I run the following:
$ Cat Input_File.txt
$ while read Otu; do echo $Otu; done <Input_File.txt
S41_Folmer_Otu96;size=12;
S78_Folmer_Otu15;size=538;
S73_Leray_Otu52;size=6;
S66_Leray_Otu93;size=6;
S10_Folmer_Otu10;size=1612;
... All 769 variables
Again, this is exactly what I expect and is correct.
But, When I do either of the following commands, nothing is printed to the screen (if I leave off the write file/append action) or to the file I need to create.
$ cat Input_File.txt | while read Otu; do grep "$Otu" -A 10 Multi_BLAST_5814.txt >> Multi_BLAST_Subset.txt; done
$ cat Input_File.txt | while read Otu; do sed -n "/$Otu/,+10p" Multi_BLAST_5814.txt >> Multi_BLAST_Subset.txt; done
Sed hangs and never closes, leaving me at a blinking cursor. Grep finishes but also gives no output. I am at a loss as to why this is not working. Everything works inidividually, so I may be left with manually searching all 769 samples copy/paste.

Answer 1

If you have access to GNU grep no need for a sed command, grep "$var" -A 10 will do the same thing and won't break if $var contains the delimiter used in your sed command.
From man grep :
-A NUM, --after-context=NUM
Print NUM lines of trailing context after matching lines.
Places a line containing a group separator (--) between
contiguous groups of matches. With the -o or --only-matching
option, this has no effect and a warning is given.

Answer 2

Not sure whether you have already attempted it but try breaking the problem into smaller chunks. Simple example below :
$ cat Input_File.txt
one
two
three
$
$ cat file.txt
This is line one
This is line two
This is line three
This is another four
This is another five
This is another six
This is another seven
$
$ cat Input_File.txt | while read var ; do echo $var ; sed -n "/$var/,+1p" file.txt ; done
one
This is line one
This is line two
two
This is line two
This is line three
three
This is line three
This is another four
$