Need help with simple comparison in AWK

Shell Programming and Scripting
1

Hi,

I'm new to AWK and I'm having problems comparing a field to a string variable.

/ARTIST/ {x = $2}
$1 ~ x {print $0}

My code tries to find a record with the string "ARTIST". Once it finds it, it stores the second field of the record into a variable. I don't know what the problem is for the second line. The point is if the first field of a record matches the variable, it will print the entire record. But for some reason, it's not working.

Thanks, need help urgently!!

2

Can you post sample data and desired output?

3

There are two input files.

The first one contains data about artists.

Peter trumpet
Bob piano
John drums

The second one contains a list of commands.

ARTIST John

For example, I want to go through the second file, so I'll store "John" into variable x. Then I want to compare x to the first fields of the first file. If it equals, then I'll print out the entire record. I'm having trouble making that comparison for the variable and the field.

4 
awk 'NR==FNR{x=$2}NR!=FNR&&$1==x' file2 file1
5

Hi Bart,

This is not giving desired out put. This is outputing only one value. if I put 2 entry in file2

ARTIST John
PLAYER Bob

Then it is giving output as Bob piano. it should give

Peter trumpet
Bob piano

I tried modified code like but not able to do correctly.

awk 'NR==FNR{x=$2}NR!=FNR&&$1 in x { print x[j]} ' f3 f2

Can some one make this correct?

Idea is to take values in array then compare

Thanks
Krsnadasa

6

Try:

awk 'NR==FNR{x[$2]=1}NR!=FNR&&$1 in x' file2 file1
7

Thanks Bart,

Can you please help me to understand the array concept here? As I am always confuse.

Here first we are first reading f2 and filling arr X like :

x[John]=1,x[Bob]=1 ...

is this is an associative array?

When we read file 1 then N==FNR is false then we are matching the pattern $1 from file1 in array..

 
awk 'NR==FNR{x[$2]=1}NR!=FNR&&$1 in x' file2 file1

Want to understand how array is formed and then serached.

Thanks
Krsnadasa

8

Yes, "x" is an associative array, with "John" and "Bob" as its keys. $1 in x is true when 1st field of file1 is among the keys of array "x" (so this is how it is being searched).