My favorite material from Codio's Unix System Basics on Coursera
sed
Delete all blank lines.
sed '/^$/d' myfile.txt
From a specific line to the end of the file.
sed '/So I tried/,$d' myfile.txt
Delete everything after a specific line and save it “in place”.
sed -i '1,/So I tried/!d' myfile.txt
awk
Using
awk
to count the number of occurrences of the word “Pooh” in the text
awk '/Pooh/{x++}END{print x}' myfile.txt
Print the number of words in a file.
awk '{ total = total + NF }; END {print total}' myfile.txt
Print the number of lines in a file.
awk 'END{print NR}' myfile.txt
Parse the comma-separated text and output two fields from each line. Don’t print the header line.
awk -F"," '{if (NR!=1){ print $1 $2 $3 }}' data.csv
Print out just the second column of the file.
awk -F"," '{print $2}' data.csv
printf
Print the result of a math equation.
printf "%d\n" $((8+4))
Print only the first 4 digits beyond the decimal point of a floating point number.
printf "%.4f\n" 3.1415926535
dd
This command copies the contents of trydd.txt to outdd.txt using the conversion ucase which turned it all to upper case characters.
dd if=trydd.txt of=outdd.txt conv=ucase
while
Create a foreground job that prints out numbers to the console in a forever loop.
COUNTER=0; while true; do printf $COUNTER; sleep 1; let COUNTER++; done