ls # lists your files in current directory, ls

statement1 && statement2 # and operator statement1 || statement2 # or operator -a # and operator inside a test conditional expression -o # or operator inside a test conditional expression

# The function refers to passed arguments by position (as if they were positional parameters), that is, $1, $2, and so forth. # $@ is equal to '$1' '$2'... '$N', where N is the number of positional parameters. $# holds the number of positional parameters.

cmd1|cmd2 # pipe; takes standard output of cmd1 as standard input to cmd2 < file # takes standard input from file > file # directs standard output to file >> file # directs standard output to file; append to file if it already exists

varname=value # defines a variable varname=value command # defines a variable to be in the environment of a particular subprocess echo $varname # checks a variable's value echo $$ # prints process ID of the current shell echo $! # prints process ID of the most recently invoked background job