awk 语言基础

awk 语言基础

awk -F\; '{print $1}' filename # print the first column
awk -F\; '{print $(NF)}' filename # print the last column

awk '/^the/' filename # the every line starting with the 'the'
awk '/the$/' filename # the every line ending with the 'the'
awk '/[0-9]/' filename # the every line contain numbers
awk '/[a-z]/' filename # the every line contain the lower capital letters
awk '/hel+0/' filename #  helllllo hello
awk '/abc|123/' filename # return for 'abc' or '123'. | --> or
FS = Input field separator value
OFS = Output field separator value
NF = Number of fields on the current line
NR = Number of records in the current file
RS = Record separator value
ORS = Output record separator
FILENAME = Current file name being processed and probably a few more
awk '{print NR}' filename # would print the line number for every line processed
## = grep -c
awk 'END{print  NR}' filename # Counts the lines in a file. similar to 'wc -l'

pipline on awk

awk 'BEGIN{print "the start"};{print}; END{print "the end"}' filename

Simple Logic

awk '{if(NR~/^2#/)print}' filename # would print line 2 from filename
awk '{if(NR~2)print}' filename # would print any line numbers contain 2 from filename
### 2, 12, 22, 32...
awk '{if(NR!~2)print}' filename # negated match
awk '{if(NR==2)print}' filename
awk '{if(NR!=2)print}' filename

OFS

awk '{OFS="\t";print $6}' filename
or
awk -F"\t" '{print $6}' filename
awk -F"\t" 'NR==1,NR==10{print $6}' filename #print the cloum 6 from line 1 to line 10;
awk -F"\t" '{print  length($5)}' filename # length() function to count the

Delete columns

awk '$1="";{print;OFS=\t}' FILENAME

Conditions

awk '$3>10' FILENAME

Deleted the line after calculation

The grammar gawk is much the same like awk but more flexible

To delete some lines which doesn’t contain Baeldung

awk '!/Baeldung/' myfile.txt > tmpfile && mv tmpfile myfile.txt

To delete lines which the second column is larger than 0.5:

gawk -i inplace '$2>=0.5' file_name

Turn one columns into few different rows

RavinderSingh13, 2016
From:

10000|[12080000000]
10002|[13075200000]
10003|[13939200000]
10004|[1347200000,133600000,1152000000,106400000,12800000,117200000,145180000,1451000000,148400000,14240000]
10005|[16000000]

To:

PARTY|PART_DT
10000|12080000000
10002|13075200000
10003|13939200000
10004|1347200000
10004|133600000
10004|1152000000
10004|106400000
10004|12800000
10004|117200000
10004|145180000
10004|1451000000
10004|148400000
10004|14240000
10005|16000000

awk -F"|" 'BEGIN{print "PARTY|PART_DT"} {gsub(/\[|\]/,X,$NF);num=split($NF, array,",");for(i=1;i<=num;i++){print $1 OFS array[i]}}' OFS="|"  Input_file

Merge one column into three columns to reduce the row number

kumaran_5555, 2011

From

AAA
BBB
CCC
DDD
EEE
FFF
GGG
HHH
III

To

AAA DDD GGG
BBB EEE HHH
CCC FFF III

awk -v col=3 '{if(NR%col){printf "%s ",$0 }else {printf "%s\n",$0}} ' test.txt

RudiC, 2019
From

A	value1
A	value2
A	value3
B	value1
B	value2
B	value3
C	value1
C	value2
C	value3

To

A	value1	value2	value3
B	value1	value2	value3
C	value1	value2	value3

awk 'LAST != $1 {printf "%s%s", DL, $0; LAST = $1; DL = RS; next}; {printf "\t%s", $2} END {printf RS}' file

Match to print

print the rows when the first column contains ‘,’

From:

123,1	123,1
123	1123,1
12,12	12314
1231	123123

To:

123,1	123,1
12,12	12314

awk -F "\t" '$1 ~ /,/ {print}' file_name

Calculation

Sum of a column

Cite:Ajo, 2015

awk -F',' '{sum+=$57;} END{print sum;}' file.txt

Mean of a column

Cite: orges, 2010

awk '{ total += $3 } END { print total/NR }' file.name

Print a column by match

CHROM	X	A	B
1	1	1	1
1	2	2	2

Let’s say, I want first two columns and the column which names is “B”:

CHROM	X	B
1	1	1
1	2	2

awk -v tmp=$(grep -i CHROM test.txt| tr '\t' '\n'| grep -wn B | awk -F: '{print $1}') '{OFS="\t"; print $1,$2,$tmp}' test.txt