UNIX for Beginners Questions & Answers

Dear all,
I have a file a.txt like below:

Code:

 1_234560_A_G_b37  1 2 1 2 2 2 ...
 1_35465767_C_T_b37  2 1 1 2 2 2 ...
 2_490638010_A_T_b37  1 2 1 2 2 2 ...
 10_4567899_T_G_b37  2 2 1 2 2 2 ...

...
what I want to do is extracting rows starting with "10_" like : 10_4567899_T_G_b37 2 2 1 2 2 2 ...
but if I use code below, I will also extract rows with '10_' in the middle of the row like: 2_490638010_A_T_b37 1 2 1 2 2 2 ...
I am wondering how I can modify my code to only extract rows starting with '10_'.
my current code:

Code:

grep '10_' a.txt>b.txt

thank you!
Lin

Use code tags for code please.

You can use ^ to specify 'beginning of line' in regular expressions.

Ir your data really all begins with a single space as shown:

Code:

grep "^ 10_" a.txt > b.txt

If it does not have that space in front:

Code:

grep "^10_" a.txt > b.txt