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

CommandMeaning
>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