awk: Adding a new column based on concatenated value of two columns - awk

I am trying to add a new column to a text file based on the concatenated values of two columns. Value is being inserted in the middle instead of the end of the string.
I am using awk. Here are two sample lines
$ head -1 file.txt
8502CC169154|02|GA|TN|89840|9|2008-11-15 00:00:00.000|2009-11-15 00:00:00.000|1|TEAM1|1639009|1000000|0|2008-11-15 00:00:00.000|2009-11-15 00:00:00.000|85|00|37421||241|20|331|1052A|5000|0|.1500|Chattanooga|47065|.000|025|35|25000|0|0|0|0|0|718||E|-17.00|-17.00|-17.00|-17.00|-17.00|-2.55|-2.55|-2.55|-2.55|D|C9N7I4115531902|-2.19|-2.19|-2.19|-2.19|-14.81|051|2008-12-31 00:00:00.000|151|2008-12-17 00:00:00.000|||AC|CC|Y||2008-12-31 00:00:00.000|.000000|A|.000000|.000000|.000000|Y|8502CC169154-8|8502CC169154|8|||122130|122130M|7764298|RA
I tried the following.
$ head -1 file.txt | awk -F'|' '{$(NF+1)=$1"-"$6;}1' OFS='|'
I am expecting a new column at the end of the string. But you can see that the concatenated field is being inserted in the middle of the string instead of the end of the string.
8502CC169154|02|GA|TN|89840|9|2008-11-15 00:00:00.000|2009-11-15 00:00:00.000|1|TEAM1|1639009|1000000|0|2008-11-15 00:00:00.000|2009-11-15 00:00:00.000|85|00|37421||241|20|331|1052A|5000|0|.1500|Chattanooga|47065|.000|025|35|25000|0|0|0|0|0|718||E|-17.00|-17.00|-17.00|-17.00|-17.00|-2.55|-2.55|-2.55|-2.55|D|C9N7I4115531902|-2.19|-2.19|-2.19|-2.19|-14.81|051|2008-12-31 00:00:00.000|151|2008|8502CC169154-9.000|||AC|CC|Y||2008-12-31 00:00:00.000|.000000|A|.000000|.000000|.000000|Y|8502CC169154-8|8502CC169154|8|||122130|122130M|7764298|RA


Your original code works for me using GNU awk but I suspect that not all awks support setting $(NF+1). To avoid that, try:
head -1 file.txt | awk -F'|' '{$0=$0 FS $1"-"$6;}1' OFS='|'
Awk is a surprising powerful language and it has all the capabilities that head has, making the pipeline unnecessary. So, for greater efficiency, try the simple command:
awk -F'|' '{print $0 FS $1"-"$6; exit}' file.txt
How it works:
-F'|'
This sets the field separator to a vertical bar.
print $0 FS $1"-"$6
This prints the output line that you want which consists of the original line, $0, followed by a field separator, FS, followed by combination of the first field, a dash, and the sixth field.
exit
After the first line is printed, this tells awk to exit. This eliminates the need for head -1.

Related

What does this Awk expression mean

I am working with bash script that has this command in it.
awk -F ‘‘ ‘/abc/{print $3}’|xargs
What is the meaning of this command?? Assume input is provided to awk.

The quick answer is it'll do different things depending on the version of awk you're running and how many fields of output the awk script produces.
I assume you meant to write:
awk -F '' '/abc/{print $3}'|xargs
not the syntactically invalid (due to "smart quotes"):
awk -F ‘’’/abc/{print $3}’|xargs
-F '' is undefined behavior per POSIX so what it will do depends on the version of awk you're running. In some awks it'll split the current line into 1 character per field. in others it'll be ignored and the line will be split into fields at every sequence of white space. In other awks still it could do anything else.
/abc/ looks for a string matching the regexp abc on the current line and if found invokes the subsequent action, in this case {print $3}.
However it's split into fields, print $3 will print the 3rd such field.
xargs as used will just print chunks of the multi-line input it's getting all on 1 line so you could get 1 line of all-fields output if you don't have many fields being output or several lines of multi-field output if you do.
I suspect the intent of that code was to do what this code actually will do in any awk alone:
awk '/abc/{printf "%s%s", sep, substr($0,3,1); sep=OFS} END{print ""}'
e.g.:
$ printf 'foo\nxabc\nyzabc\nbar\n' |
awk '/abc/{printf "%s%s", sep, substr($0,3,1); sep=OFS} END{print ""}'
b a

Can I delete a field in awk?

This is test.txt:
0x01,0xDF,0x93,0x65,0xF8
0x01,0xB0,0x01,0x03,0x02,0x00,0x64,0x06,0x01,0xB0
0x01,0xB2,0x00,0x76
If I run
awk -F, 'BEGIN{OFS=","}{$2="";print $0}' test.txt
the result is:
0x01,,0x93,0x65,0xF8
0x01,,0x01,0x03,0x02,0x00,0x64,0x06,0x01,0xB0
0x01,,0x00,0x76
The $2 wasn't deleted, it just became empty.
I hope, when printing $0, that the result is:
0x01,0x93,0x65,0xF8
0x01,0x01,0x03,0x02,0x00,0x64,0x06,0x01,0xB0
0x01,0x00,0x76

All the existing solutions are good though this is actually a tailor made job for cut:
cut -d, -f 1,3- file
0x01,0x93,0x65,0xF8
0x01,0x01,0x03,0x02,0x00,0x64,0x06,0x01,0xB0
0x01,0x00,0x76
If you want to remove 3rd field then use:
cut -d, -f 1,2,4- file
To remove 4th field use:
cut -d, -f 1-3,5- file

I believe simplest would be to use sub function to replace first occurrence of continuous ,,(which are getting created after you made 2nd field NULL) with single ,. But this assumes that you don't have any commas in between field values.
awk 'BEGIN{FS=OFS=","}{$2="";sub(/,,/,",");print $0}' Input_file
2nd solution: OR you could use match function to catch regex from first comma to next comma's occurrence and get before and after line of matched string.
awk '
match($0,/,[^,]*,/){
print substr($0,1,RSTART-1)","substr($0,RSTART+RLENGTH)
}' Input_file

It's a bit heavy-handed, but this moves each field after field 2 down a place, and then changes NF so the unwanted field is not present:
$ awk -F, -v OFS=, '{ for (i = 2; i < NF; i++) $i = $(i+1); NF--; print }' test.txt
0x01,0x93,0x65,0xF8
0x01,0x01,0x03,0x02,0x00,0x64,0x06,0x01
0x01,0x00,0x76
$
Tested with both GNU Awk 4.1.3 and BSD Awk ("awk version 20070501" on macOS Mojave 10.14.6 — don't ask; it frustrates me too, but sometimes employers are not very good at forward thinking). Setting NF may or may not work on older versions of Awk — I was a little surprised it did work, but the surprise was a pleasant one, for a change.

If Awk is not an absolute requirement, and the input is indeed as trivial as in your example, sed might be a simpler solution.
sed 's/,[^,]*//' test.txt
This is especially elegant if you want to remove the second field. A more generic approach to remove, the nth field would require you to put in a regex which matches the first n - 1 followed by the nth, then replace that with just the the first n - 1.
So for n = 4 you'd have
sed 's/\([^,]*,[^,]*,[^,]*,\)[^,]*,/\1/' test.txt
or more generally, if your sed dialect understands braces for specifying repetitions
sed 's/\(\([^,]*,\)\{3\}\)[^,]*,/\1/' test.txt
Some sed dialects allow you to lose all those pesky backslashes with an option like -r or -E but again, this is not universally supported or portable.
In case it's not obvious, [^,] matches a single character which is not (newline or) comma; and \1 recalls the text from first parenthesized match (back reference; \2 recalls the second, etc).
Also, this is completely unsuitable for escaped or quoted fields (though I'm not saying it can't be done). Every comma acts as a field separator, no matter what.

With GNU sed you can add a number modifier to substitute nth match of non-comma characters followed by comma:
sed -E 's/[^,]*,//2' file

Using awk in a regex-free way, with the option to choose which line will be deleted:
awk '{ col = 2; n = split($0,arr,","); line = ""; for (i = 1; i <= n; i++) line = line ( i == col ? "" : ( line == "" ? "" : "," ) arr[i] ); print line }' test.txt
Step by step:
{
col = 2 # defines which column will be deleted
n = split($0,arr,",") # each line is split into an array
# n is the number of elements in the array
line = "" # this will be the new line
for (i = 1; i <= n; i++) # roaming through all elements in the array
line = line ( i == col ? "" : ( line == "" ? "" : "," ) arr[i] )
# appends a comma (except if line is still empty)
# and the current array element to the line (except when on the selected column)
print line # prints line
}

Another solution:
You can just pipe the output to another sed and squeeze the delimiters.
$ awk -F, 'BEGIN{OFS=","}{$2=""}1 ' edward.txt | sed 's/,,/,/g'
0x01,0x93,0x65,0xF8
0x01,0x01,0x03,0x02,0x00,0x64,0x06,0x01,0xB0
0x01,0x00,0x76
$

Commenting on the first solution of #RavinderSingh13 using sub() function:
awk 'BEGIN{FS=OFS=","}{$2="";sub(/,,/,",");print $0}' Input_file
The gnu-awk manual: https://www.gnu.org/software/gawk/manual/html_node/Changing-Fields.html
It is important to note that making an assignment to an existing field changes the value of $0 but does not change the value of NF, even when you assign the empty string to a field." (4.4 Changing the Contents of a Field)
So, following the first solution of RavinderSingh13 but without using, in this case,sub() "The field is still there; it just has an empty value, delimited by the two colons":
awk 'BEGIN {FS=OFS=","} {$2="";print $0}' file
0x01,,0x93,0x65,0xF8
0x01,,0x01,0x03,0x02,0x00,0x64,0x06,0x01,0xB0
0x01,,0x00,0x76

My solution:
awk -F, '
{
regex = "^"$1","$2
sub(regex, $1, $0);
print $0;
}'
or one line code:
awk -F, '{regex="^"$1","$2;sub(regex, $1, $0);print $0;}' test.txt
I found that OFS="," was not necessary

I would do it following way, let file.txt content be:
0x01,0xDF,0x93,0x65,0xF8
0x01,0xB0,0x01,0x03,0x02,0x00,0x64,0x06,0x01,0xB0
0x01,0xB2,0x00,0x76
then
awk 'BEGIN{FS=",";OFS=""}{for(i=2;i<=NF;i+=1){$i="," $i};$2="";print}' file.txt
output
0x01,0x93,0x65,0xF8
0x01,0x01,0x03,0x02,0x00,0x64,0x06,0x01,0xB0
0x01,0x00,0x76
Explanation: I set OFS to nothing (empty string), then for 2nd and following column I add , at start. Finally I set what is now comma and value to nothing. Keep in mind this solution would need rework if you wish to remove 1st column.

How can I use awk to print a numeric index based on a matching pattern?

I have a comma-separated file with two columns like so:
A,france
B,france
C,germany
D,germany
E,germany
F,spain
G,spain
I want to use awk (or any similar tool) to print a numeric value for each of the different groups (countries in this example). i.e.
A,france,1
B,france,1
C,germany,2
D,germany,2
E,germany,2
F,spain,3
G,spain,3
Is there a straightforward way to achieve this without having to specify every single group manually?

Using an associative array t for the team numbers. For each line, test if the team is not yet a key in the array (value will equate to empty string), and in that case, increment the value of counter i and set the value in the t array to the counter value after this increment. Then print the whole line ($0), followed by the value looked up from the associative array.
The -F, -v OFS=, uses field separator , on both input and output.
awk -F, -v OFS=, '{if (t[$2]=="") {t[$2]=++i}; print $0,t[$2]}' filename
gives
A,france,1
B,france,1
C,germany,2
D,germany,2
E,germany,2
F,spain,3
G,spain,3

This one-liner works no matter the countries are sorted or not in the input file:
awk -F, -v OFS=',' '{a[$2]=a[$2]?a[$2]:++i}$3=a[$2]' file
For example:
$ awk -F, -v OFS=',' '{a[$2]=a[$2]?a[$2]:++i}$3=a[$2]' f
A,france,1
B,france,1
C,germany,2
D,germany,2
E,germany,2
F,spain,3
G,spain,3
H,germany,2
I,germany,2
J,spain,3

awk to parse field if specific value is in another

In the awk below I am trying to parse $2 using the _ only if $3 is a specific valus (ID). I am reading that parsed value into an array and going to use it as a key in a lookup. The awk does execute but the entire line 2 or line with ID in $3 prints not just the desired. The print statement is only to see what results (for testing only) and will not be part of the script. Thank you :).
awk
awk -F'\t' '$3=="ID"
f="$(echo $2|cut -d_ -f1,1)"
{
print $f
}' file
file tab-delimited
R_Index locus type
17 chr20:31022959 NON
18 chr11:118353210-chr9:20354877_KMT2A-MLLT3.K8M9 ID
desired
$f = chr11:118353210-chr9:20354877

Not completely clear, could you please try following.
awk '{split($2,array,"_");if(array[2]=="KMT2A-MLLT3.K8M9"){print array[1]}}' Input_file
Or if you want top change 2nd field's value along with printing all lines then try following once.
awk '{split($2,array,"_");if(array[2]=="KMT2A-MLLT3.K8M9"){$2=array[1]}} 1' Input_file

Output field separators in awk after substitution in fields

Is it always the case, after modifying a specific field in awk, that information on the output field separator is lost? What happens if there are multiple field separators and I want them to be recovered?
For example, suppose I have a simple file example that contains:
a:e:i:o:u
If I just run an awk script, which takes account of the input field separator, that prints each line in my file, such as running
awk -F: '{print $0}' example
I will see the original line. If however I modify one of the fields directly, e.g. with
awk -F: '{$2=$2"!"; print $0}' example
I do not get back a modified version of the original line, rather I see the fields separated by the default whitespace separator, i.e:
a e! i o u
I can get back a modified version of the original by specifying OFS, e.g.:
awk -F: 'BEGIN {OFS=":"} {$2=$2"!"; print $0}' example
In the case, however, where there are multiple potential field separators but in the case of multiple separators is there a simple way of restoring the original separators?
For example, if example had both : and ; as separators, I could use -F":|;" to process the file but OFS would no be sufficient to restore the original separators in their relative positions.
More explicitly, if we switched to example2 containing
a:e;i:o;u
we could use
awk -F":|;" 'BEGIN {OFS=":"} {$2=$2"!"; print $0}' example2
(or -F"[:;]") to get
a:e!:i:o:u
but we've lost the distinction between : and ; which would have been maintained if we could recover
a:e!;i:o;u

You need to use GNU awk for the 4th arg to split() which saves the separators, like RT does for RS:
$ awk -F'[:;]' '{split($0,f,FS,s); $2=$2"!"; r=s[0]; for (i=1;i<=NF;i++) r=r $i s[i]; $0=r} 1' file
a:e!;i:o;u
There is no automatically populated array of FS matching strings because of how expensive it'd be in time and memory to store the string that matches FS every time you split a record into fields. Instead the GNU awk folks provided a 4th arg to split() so you can do it yourself if/when you want it. That is the result of a long conversation a few years ago in the comp.lang.awk newsgroup between experienced awk users and gawk providers before all agreeing that this was the best approach.
See split() at https://www.gnu.org/software/gawk/manual/gawk.html#String-Functions.