How to Make Awk Use the Variable Created in Bash Script

How to make AWK use the variable created in Bash Script

You can use it like this.

for i in `find $1 -name \*.jar`
do
jar tvf $i| awk -F '/' '/class/{print "'${i}'" " " $NF }' >> $classFile
done

You should use

"'${i}'"

in AWK to use the

$i

created in Bash Script.

How do I use shell variables in an awk script?

#Getting shell variables into awk
may be done in several ways. Some are better than others. This should cover most of them. If you have a comment, please leave below.                                                                                    v1.5

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Using -v (The best way, most portable)

Use the -v option: (P.S. use a space after -v or it will be less portable. E.g., awk -v var= not awk -vvar=)

variable="line one\nline two"
awk -v var="$variable" 'BEGIN {print var}'
line one
line two

This should be compatible with most awk, and the variable is available in the BEGIN block as well:

If you have multiple variables:

awk -v a="$var1" -v b="$var2" 'BEGIN {print a,b}'

Warning. As Ed Morton writes, escape sequences will be interpreted so \t becomes a real tab and not \t if that is what you search for. Can be solved by using ENVIRON[] or access it via ARGV[]

PS If you have vertical bar or other regexp meta characters as separator like |?( etc, they must be double escaped. Example 3 vertical bars ||| becomes -F'\\|\\|\\|'. You can also use -F"[|][|][|]".

Example on getting data from a program/function inn to awk (here date is used)

awk -v time="$(date +"%F %H:%M" -d '-1 minute')" 'BEGIN {print time}'

Example of testing the contents of a shell variable as a regexp:

awk -v var="$variable" '$0 ~ var{print "found it"}'

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Variable after code block

Here we get the variable after the awk code. This will work fine as long as you do not need the variable in the BEGIN block:

variable="line one\nline two"
echo "input data" | awk '{print var}' var="${variable}"
or
awk '{print var}' var="${variable}" file

• Adding multiple variables:

awk '{print a,b,$0}' a="$var1" b="$var2" file

• In this way we can also set different Field Separator FS for each file.

awk 'some code' FS=',' file1.txt FS=';' file2.ext

• Variable after the code block will not work for the BEGIN block:

echo "input data" | awk 'BEGIN {print var}' var="${variable}"

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Here-string

Variable can also be added to awk using a here-string from shells that support them (including Bash):

awk '{print $0}' <<< "$variable"
test

This is the same as:

printf '%s' "$variable" | awk '{print $0}'

P.S. this treats the variable as a file input.

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ENVIRON input

As TrueY writes, you can use the ENVIRON to print Environment Variables.
Setting a variable before running AWK, you can print it out like this:

X=MyVar
awk 'BEGIN{print ENVIRON["X"],ENVIRON["SHELL"]}'
MyVar /bin/bash

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ARGV input

As Steven Penny writes, you can use ARGV to get the data into awk:

v="my data"
awk 'BEGIN {print ARGV[1]}' "$v"
my data

To get the data into the code itself, not just the BEGIN:

v="my data"
echo "test" | awk 'BEGIN{var=ARGV[1];ARGV[1]=""} {print var, $0}' "$v"
my data test

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Variable within the code: USE WITH CAUTION

You can use a variable within the awk code, but it's messy and hard to read, and as Charles Duffy points out, this version may also be a victim of code injection. If someone adds bad stuff to the variable, it will be executed as part of the awk code.

This works by extracting the variable within the code, so it becomes a part of it.

If you want to make an awk that changes dynamically with use of variables, you can do it this way, but DO NOT use it for normal variables.

variable="line one\nline two"
awk 'BEGIN {print "'"$variable"'"}'
line one
line two

Here is an example of code injection:

variable='line one\nline two" ; for (i=1;i<=1000;++i) print i"'
awk 'BEGIN {print "'"$variable"'"}'
line one
line two
1
2
3
.
.
1000

You can add lots of commands to awk this way. Even make it crash with non valid commands.

One valid use of this approach, though, is when you want to pass a symbol to awk to be applied to some input, e.g. a simple calculator:

$ calc() { awk -v x="$1" -v z="$3" 'BEGIN{ print x '"$2"' z }'; }

$ calc 2.7 '+' 3.4
6.1

$ calc 2.7 '*' 3.4
9.18

There is no way to do that using an awk variable populated with the value of a shell variable, you NEED the shell variable to expand to become part of the text of the awk script before awk interprets it.

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Extra info:

Use of double quote

It's always good to double quote variable "$variable"

If not, multiple lines will be added as a long single line.

Example:

var="Line one
This is line two"

echo $var
Line one This is line two

echo "$var"
Line one
This is line two

Other errors you can get without double quote:

variable="line one\nline two"
awk -v var=$variable 'BEGIN {print var}'
awk: cmd. line:1: one\nline
awk: cmd. line:1:    ^ backslash not last character on line
awk: cmd. line:1: one\nline
awk: cmd. line:1:    ^ syntax error

And with single quote, it does not expand the value of the variable:

awk -v var='$variable' 'BEGIN {print var}'
$variable

More info about AWK and variables

Read this faq.

How to use awk build in variable in shell script

Something like that?

temp=$(awk '{print $NF}' aa)

Use variable updated in awk bash script

You can do the entire loop in AWK:

awk -v Q="$Q" -v k="$k" -v N="$N" -v col="$col_prob" '{ p_k=Q*k/N; k++ } $col+0<=p_k { print $0 }' $1 > $out_file

This solution is shorter and it will work faster than your bash loop.

I don't know what the values of your variables Q, k, N, col_prob are but this works:

Q=10e-10
k=1
N=10e+10
col_prob=7
awk -v Q="$Q" -v k="$k" -v N="$N" -v col="$col_prob" '{ p_k=Q*k/N; k++ } $col+0<=p_k { print $0 }' YOURFILE

Output:

XXX 405 0 307 98 G 3.9158562774e-33

P.S. Please, choose "best answer" if an answer works for you. I see from your history that you never did this before. You should.

using awk in Bash script

The crux of the problem is that you're trying to use a single-quoted string as if it were a double-quoted one.

What you meant to do when you used:

'\$2 == "$fruit"' # DOES NOT WORK - nothing is escaped or expanded

was:

"\$2 == \"$fruit\""  # keep literal $2, expand $fruit

Anything inside a single-quoted shell string is taken literally, so variable references aren't expanded, and nothing needs escaping - nor indeed can be escaped (the \ would become a literal part of the string too).

That said, it's better to keep the worlds of the shell and the Awk script separate, so as to prevent confusion, which means:

• Use a single-quoted string as the Awk script.
• Pass any shell-variable values to the script via Awk's -v option to create Awk variables.

If we put it all together:

a=$(awk -F'[: ]' -v fruit="$fruit" '$2 == fruit' data.txt)

Note that I've used modern command-substitution syntax $(...), which is preferable to legacy syntax `...`.

awk variables to bash

Sounds like this question: setting multiple variables.
In your case, you can try something like:

awk '{ print($1 " " $2 " " $3 " " $4 " " $5); }' file.dat | { read a b c d e; echo $a $b $c $d $e; }

Or if you need to loop over lines from your file.dat:

awk '{ print( $1 " " $2 " " $3 " " $4 " " $5); }' file.dat | \
{ while read a b c d e; do echo $a $b $c $d $e; done; }

Awk use shell variable inside begin block

Your command is literally matching s in every line.

You should be using ~ operator:

awk -v s="$site" 'BEGIN {IGNORECASE = 1} $0 ~ s' sites.txt

Note that IGNORECASE = 1 is a gnu awk feature and if you want a POSIX compliant way then use:

awk -v s="$site" 'tolower($0) ~ tolower(s)' sites.txt

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