Operators

<          # connects the STDIN to contents of an existing file
>          # redirects STDOUT, replaces file's existing contents
>>         # redirects STDOUT, appends to a file
0<, 1>, 2> # specifically target where from and to send STDIN, STDOUT, STDERR
2>&1       # point fd2 to where fd1 is pointing, the & says this is a fd not a file
    1>/dev/null 2>&1 # send fd1 to /dev/null and send fd2 to where fd1 is pointing
|          # connect fd1 of of one process to fd0 of the next via kernel pipe()

>&         # not POSIX: >&file redirects both STDOUT and STDERR
    >& /dev/null # updates fd1 and 2 (stdout and stderr) at the same time

find / -name core 2> /dev/null # redirect STDERR to null driver
find / -name core 1> ~/results.txt 2>/dev/null # redirect STDOUT

# Using tee, (origin is from plumbing T which split in two directions)
# it reads STDIN, writes to STDOUT and also the named file
find / -name core 2> /dev/null | tee ~/results.txt

x && y     # only do Y if X passes (return 0)
x || y     # only do Y if X fails (return != 0)
&          # If a command is terminated &, the shell executes the command in the background in a subshell
;          # split a single line into multiple commands

# Not an operator, an convience escape char, joins lines since shells only accept single lines
# To use, type a '\' and press enter to go to the next line
\          # combine multiple lines into a single command

cd foo || echo "No such directory"

# 1> - updates pointer for fd1 from (say) /dev/pts/0 (terminal) to /dev/null,
#      nothing is closed or open the data structure is just updated
# 2>&1 - copy fd1's target (file descriptor) into fd2's slot (not a reference)
# & - finally run in background
hugo server 1>/dev/null 2>&1 &
# You can also do 1> implicitly as mentioned above with just >