unix awk column equal to a variable

Question

I want to print the lines that with two columns equal to a variable, for example, input:

2607s1  NC_000067.6 95.92   49  1   1   3   50  1e-14   84.2
2607s1  NC_000067.6 97.73   44  1   0   7   50  4e-14   84.2
2607s1  NC_000067.6 97.67   43  1   0   8   50  1e-13   75.0

and variables for first and last column:

a="2607s1"; b="84.2"

and using awk command, output:

2607s1  NC_000067.6 95.92   49  1   1   3   50  1e-14   84.2
2607s1  NC_000067.6 97.73   44  1   0   7   50  4e-14   84.2

I have tried the following but not work:

awk -v '$1==$a' && '$10==$b' test_file
cat test_file|awk '$1=="($a)" && $10=="($b)"'
cat test_file|awk '$1==($a) && $10==($b)'
cat test_file|awk '$1=="$a" && $10=="$b"'

Moreover, I am running it in a while loop, so the $a and $b keep changing Please help..

Answer 1

You are passing the shell variables to the awk command using a wrong method. It should be like

awk -v a="$a" -v b="$b" '$1==a && $10 == b' 

What it does

• -v a="$a" creates an awk variable a and assigns the value of shell variable $a to it.

• -v b="$b" Creates awk variable b.

OR

awk '$1==a && $10 == b' a="$a" b="$b" file

---

When you write a statement like this

awk -v '$1==$a' && '$10==$b' test_file

awk doesn't know what $a $b is because both are shell variables.

And the correct method of using -v for passing shell variables is as in demonstrated in the examples.

From awk manuals

-v var=val

   --assign var=val

    Assign  the  value  val to the variable var, before execution of
    the program begins.  Such variable values are available  to  the
    BEGIN block of an AWK program.

---

Test

$ cat file 
2607s1  NC_000067.6 95.92   49  1   1   3   50  1e-14   84.2
2607s1  NC_000067.6 97.73   44  1   0   7   50  4e-14   84.2
2607s1  NC_000067.6 97.67   43  1   0   8   50  1e-13   75.0

$ a="2607s1"; b="84.2"

$ awk -v a="$a" -v b="$b" '$1==a && $10 == b' file 
2607s1  NC_000067.6 95.92   49  1   1   3   50  1e-14   84.2
2607s1  NC_000067.6 97.73   44  1   0   7   50  4e-14   84.2