A.1. Common features

The following features are standard in every shell. Note that the stop, suspend, jobs, bg and fg commands are only available on systems that support job control.

Table A-1. Common Shell Features

>Redirect output
>>Append to file
<Redirect input
<<"Here" document (redirect input)
|Pipe output
&Run process in background.
;Separate commands on same line
*Match any character(s) in filename
?Match single character in filename
[ ]Match any characters enclosed
( )Execute in subshell
` `Substitute output of enclosed command
" "Partial quote (allows variable and command expansion)
' 'Full quote (no expansion)
\Quote following character
$varUse value for variable
$$Process id
$0Command name
$nnth argument (n from 0 to 9)
#Begin comment
bgBackground execution
breakBreak from loop statements
cdChange directories
continueResume a program loop
echoDisplay output
evalEvaluate arguments
execExecute a new shell
fgForeground execution
jobsShow active jobs
killTerminate running jobs
newgrpChange to a new group
shiftShift positional parameters
stopSuspend a background job
suspendSuspend a foreground job
timeTime a command
umaskSet or list file permissions
unsetErase variable or function definitions
waitWait for a background job to finish