cp command

To copy a file

cp ~/Desktop/foo.txt ~/Downloads/foo.txt

To copy a directory

cp -r ~/Desktop/cruise_pics/ ~/Pictures/

To create a copy but ask to overwrite if the destination file already exists

cp -i ~/Desktop/foo.txt ~/Documents/foo.txt

To create a backup file with date

cp foo.txt{,."$(date +%Y%m%d-%H%M%S)"}

cat command

To display the contents of a file

cat <file>

To display file contents with line numbers

cat -n <file>

To display file contents with line numbers (blank lines excluded)

cat -b <file>

tee command

To tee stdout to

ls | tee <outfile>

To tee stdout and append to

ls | tee -a <outfile>

To tee stdout to the terminal, and also pipe it into another program for further processing

ls | tee /dev/tty | xargs printf "\033[1;34m%s\033[m\n"

sort command

To sort a file

sort <file>

To sort a file by keeping only unique

sort -u <file>

To sort a file and reverse the result

sort -r <file>

To sort a file randomly

sort -R <file>