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3.5 Differing Features

The following table displays features that are different among the three shells.

sh ksh csh Meaning/Action
$ $ % Prompt.
  >| >! Force redirection.
    >>! Force append.
> file 2>&1 > file 2>&1 >& file Combine stdout and stderr.
    { } Expand elements in list.
` ` ` ` ` `

Substitute output of enclosed command.

  $( )  

Substitute output of enclosed command. (Preferred form.)

$HOME $HOME $home Home directory.
  ~ ~ Home directory symbol.
var = value var = value set var =value Variable assignment.
export var export var = val setenv var val

Set environment variable.

  ${ nn }  

More than nine args can be referenced.

"$@" "$@"  

All args as separate words.

$# $# $#argv

Number of arguments.

$? $? $status

Exit status.

$! $!  

Background exit status.

$- $-  

Current options.

.   file .   file source file

Read commands in file .

  alias x =y alias x y

Name x stands for y .

case case switch/case

Choose alternatives.

  cd ~- popd/pushd

Switch directories.

done done end

End a loop statement.

esac esac endsw

End case or switch .

exit [ n ] exit [ n ] exit [( expr )]

Exit with a status.

for/do for/do foreach

Loop through variables.

  print -r glob

Ignore echo escapes.

hash alias -t hashstat

Display hashed commands (tracked aliases).

hash cmds alias -t cmds rehash

Remember command locations.

hash -r PATH=$PATH unhash

Forget command locations.

  history history

List previous commands.

  r !!

Redo previous command.

  r str ! str

Redo command that starts with str .

  r x = cmd ! cmd :s/ x/y

Edit command, then execute.

if [ $i -eq 5 ] if ((i==5)) if ($i==5)

Sample if statement.

fi fi endif

End if statement.

ulimit ulimit limit

Set resource limits.

pwd pwd dirs

Print working directory.

read read $<

Read from standard input.

trap 2 trap 2 onintr

Ignore interrupts.

  unalias unalias

Remove aliases.

until/do until/do  

Begin until loop.

while/do while/do while

Begin while loop.

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