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Using variable within awk

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# 1  
Old 09-18-2013
Using variable within awk
Hi All,

I have a tab-delimited input file in which the 7th column contains the date in the format given below
Code:
Aug 29 2013 12:00AM

I have assigned this date value to a variable like

Code:
d1="Aug 29 2013 12:00AM"

I want to compare the 7th column in the file with this variable d1 and if it matches, I want the whole line to be copied to a separate file.

I am doing the below but not getting the desired result

Code:
cat input_file | awk -F"\t" '{if ($7=="$d1") print $0}'

Can you help?

Thanks
# 2  
Old 09-18-2013
Hi,
You can try:
Code:
cat input_file | awk -F"\t" '{if ($7=="'$d1'") print $0}'

Regards.
# 3  
Old 09-18-2013
it's giving the below error:

Code:
 syntax error The source line is 1.
 The error context is
                {if >>>  ($7=="Aug <<<
 awk: The statement cannot be correctly parsed.
 The source line is 1.
        awk: There is a missing } character.
        awk: There is a missing ) character.

# 4  
Old 09-18-2013
Use -v for using variable in awk. and avoid use of cat if you are using awk.
Code:
d1="Aug 29 2013 12:00AM"

 awk -F"\t" -v D1="$d1" '{if ($7==D1) print $0}' input_file

# 5  
Old 09-18-2013
Yep,
I forget to protect variable:
Code:
cat input_file | awk -F"\t" '{if ($7=="'"$d1"'") print $0}'

First double quote for awk
simple quote to come back shell for interpreting variable d1
second double quote for protect space in variable value

Regards.
# 6  
Old 09-18-2013
You should not add variable to awk this way, do like pamu shows, or like this.
awk -F"\t" '{if ($7==D1) print $0}' D1="$d1" input_file

If yo do not have space, only tab, you can remove the field separator too.
awk '{if ($7==D1) print $0}' D1="$d1" input_file
# 7  
Old 09-18-2013
Quote:
Originally Posted by disedorgue
Yep,
I forget to protect variable:
Code:
cat input_file | awk -F"\t" '{if ($7=="'"$d1"'") print $0}'

First double quote for awk
simple quote to come back shell for interpreting variable d1
second double quote for protect space in variable value

Regards.
You get several Useless Use of Cat Awards

There are two reliable ways to get a variable into awk, that is neither of them.

Code:
# method 1
awk -v VAR=value '{ ... }'

# method 2
awk '{ ... }' VAR=value

Your method is prone to syntax errors, should your variable accidentally contain any quotes or awk code.
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