CODEWITHSUNDEEP
bashvariablesunixawkwhile-loop
once
once

Reputation: 1399

unix awk column equal to a variable

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..

Upvotes: 6

Views: 18350

Answers (3)

nu11p01n73R
nu11p01n73R

Reputation: 26667

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

Upvotes: 15

RémiH
RémiH

Reputation: 41

You can also do this (this avoids using -v parameters)

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

The quote ' just before $a will turn off string interpretation.

The quote ' just after $a will turn on string interpretation.

$a is in this way interpreted and replaced by its value.

Upvotes: 4

Avinash Raj
Avinash Raj

Reputation: 174696

You may try the below awk command.

awk -v var1="$a" -v var2="$b" '$1==var1&&$NF==var2' file

Upvotes: 1

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