Linux in a Nutshell, 6th Edition

Command Forms

Syntax	Effect
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.

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 file if it contains the pattern;
$ grep XX file || echo "XX not ...