sed -e 's/pattern1/pattern2/g' file1 > file2
set x = 2 # variable
sed -e "s/pattern1/${x}/g" file1 > file2
sed -i 128,+23d inputfile # delete 23 lines starting from line 128 of inputfile
tail -n 100 inputfile > outputfile # take the last 100 lines of inputfile into outputfile
cut -d " " -f 2- inputfile > outputfile # cut columns of inputfile, save from fileds 2. separator between fields is space " "
cat inputfile| awk '{ print $7 }' > outputfile # take column 7 of inputfile and put it in outputfile
perl -ne 'print if $. % 3 == 1' < input.txt > output.txt # output every 3 lines of input.txt to output.txt
grep '^6500' input.txt > output.txt # grep lines starting with 6500
grep '6500$' input.txt > output.txt # grep lines ending with 6500
grep -v 6500 input.txt > output.txt # grep lines not containing 6500
paste file1 file2 | column -s $'\t' -t > file # paste file2 to the right of file1 column-wise and store in file
ls -l directory | wc -l # count number of files in folder