Unix in a Nutshell, 4th Edition

Command Forms

cmd &	Execute cmd in background.
cmd1 ; cmd2	Command sequence; execute multiple cmds on the same line.
{ cmd1 ; cmd2 ; }	Execute commands as a group in the current shell.
( cmd1 ; cmd2 )	Execute commands as a group in a subshell.
cmd1 | cmd2	Pipe; use output from cmd1 as input to cmd2.
cmd1 ' cmd2 '	Command substitution; use cmd2 output as arguments to cmd1.
cmd1 $( cmd2 )	POSIX shell command substitution; nesting is allowed.
cmd $(( expression ))	POSIX shell arithmetic substitution. Use the result of expression as argument to cmd.
cmd1 && cmd2	AND; execute cmd1 and then (if cmd1 succeeds) cmd2. This is a “short-circuit” operation; cmd2 is never executed if cmd1 fails.
cmd1 || cmd2	OR; execute either cmd1 or (if cmd1 fails) cmd2. This is a “short-circuit” operation; cmd2 is never executed if cmd1 succeeds.
! cmd	NOT; execute cmd, and produce a zero exit status if cmd exits with a nonzero status. Otherwise, produce a nonzero status when cmd exits with a zero status. Not ksh88.

Examples

    $ nroff file > file.txt &                  
                     Format in the background
    $ cd; ls                                   
                     Execute sequentially
    $ (date; who; pwd) > logfile               
                     All output is redirected
    $ sort file | pr -3 | lp                   
                     Sort file, page output, then print
    $ vi 'grep -l ifdef *.c'                   
                     Edit files found by grep
    $ egrep '(yes|no)' 'cat list'              
                     Specify a list of files to search
    $ egrep '(yes|no)' $(cat list)             
                     POSIX version of previous
    $ egrep '(yes|no)' $(< list)               
                     Faster, not in POSIX
    $ grep XX file && lp file                  
                     Print ...