Sed grep awk

FS is any single character or regular expression which you want to use as a input field separator.
OFS is an output equivalent of awk FS variable. By default awk OFS is a single space character.
RS defines a line.
ORS is an Output equivalent of RS. Each record in the output will be printed with this delimiter.
NR gives you the total number of records being processed or line number.
NF gives you the total number of fields in a record

Chiude le parole cercate tra parentesi, case insensitive
sed -e 's/\bthy\b/{&}/gi'

Inverte l’ordine dei gruppi di cifre
sed 's/$[0-9]\{4\}$ $[0-9]\{4\} $$[0-9]\{4\} $$[0-9]\{4\}$/\4 \3\2\1/g'

$ cat awk_avg.awk
{
avg=($2+$3+$4)/3;

if (avg \< 50\) grade="FAIL";  
else if (avg\>=50 && avg\<60) grade="C";  
else if (avg\>=60 && avg\<80) grade="B";  
else grade="A";

print $0,":",grade;

}
OUTPUT
$ awk -f awk_avg.awk colonne.txt
A 25 27 50 : FAIL
B 35 37 75 : FAIL
C 75 78 80 : B
D 99 88 76 : A
---

$ cat merge_lines.awk
BEGIN { evenLine = 0; }
{
if ( evenLine == 0 ){
line = $0;
evenLine = 1;
}
else {
print line ";" $0;
evenLine = 0;
}
}
OR
awk 'ORS=NR%2?";":"\n"'
OR
paste -d';' - -

Stampa per le righe con meno di 4 colonne
awk 'NF\<4{print "Not all scores are available for "$1}' colonne.txt

GREP
grep -e "\bthe\b"
egrep -i "\bthe\b"
# le righe che non contengono that
grep -vie "\bthat\b"

PYTHON

regex_pattern = r"^...\....\....\....$" # Do not delete 'r'.