C.2.
Differing features
The table below shows major differences between the standard
shell (sh), Bourne Again SHell
(bash), Korn shell (ksh) and the C shell (csh).
 |
Shell
compatibility |
| |
Since the Bourne Again SHell is a superset of
sh, all sh commands will also work in bash - but not vice versa. bash has many more features of its own,
and, as the table below demonstrates, many features
incorporated from other shells.
Since the Turbo C shell is a superset of csh, all csh
commands will work in tcsh, but
not the other way round.
|
Table C-2. Differing Shell Features
| sh |
bash |
ksh |
csh |
Meaning/Action |
| $ |
$ |
$ |
% |
Default user
prompt |
| |
>| |
>| |
>! |
Force redirection |
| > file
2>&1 |
&> file
or > file 2>&1 |
> file
2>&1 |
>& file |
Redirect stdout and
stderr to file |
| |
{
} |
|
{
} |
Expand elements in
list |
| `command` |
`command` or $(command) |
$(command) |
`command` |
Substitute output of
enclosed command |
| $HOME |
$HOME |
$HOME |
$home |
Home directory |
| |
~ |
~ |
~ |
Home directory
symbol |
| |
~+, ~-,
dirs |
~+, ~- |
=-, =N |
Access directory
stack |
| var=value |
VAR=value |
var=value |
set
var=value |
Variable
assignment |
| export var |
export VAR=value |
export var=val |
setenv var
val |
Set environment
variable |
| |
${nnnn} |
${nn} |
|
More than 9 arguments
can be referenced |
| "$@" |
"$@" |
"$@" |
|
All arguments as
separate words |
| $# |
$# |
$# |
$#argv |
Number of
arguments |
| $? |
$? |
$? |
$status |
Exit status of the
most recently executed command |
| $! |
$! |
$! |
|
PID of most recently
backgrounded process |
| $- |
$- |
$- |
|
Current options |
| .
file |
source file or
. file |
.
file |
source file |
Read commands in
file |
| |
alias x='y' |
alias x=y |
alias x y |
Name x stands for command y |
| case |
case |
case |
switch or case |
Choose
alternatives |
| done |
done |
done |
end |
End a loop
statement |
| esac |
esac |
esac |
endsw |
End case or switch |
| exit n |
exit n |
exit n |
exit (expr) |
Exit with a
status |
| for/do |
for/do |
for/do |
foreach |
Loop through
variables |
| |
set
-f , set
-o
nullglob|dotglob|nocaseglob|noglob |
|
noglob |
Ignore substitution
characters for filename generation |
| hash |
hash |
alias -t |
hashstat |
Display hashed
commands (tracked aliases) |
| hash cmds |
hash cmds |
alias -t cmds |
rehash |
Remember command
locations |
| hash -r |
hash -r |
|
unhash |
Forget command
locations |
| |
history |
history |
history |
List previous
commands |
| |
ArrowUp+Enter or
!! |
r |
!! |
Redo previous
command |
| |
!str |
r
str |
!str |
Redo last command that
starts with "str" |
| |
!cmd:s/x/y/ |
r
x=y cmd |
!cmd:s/x/y/ |
Replace "x" with "y"
in most recent command starting with "cmd", then execute. |
| if
[ $i -eq 5 ] |
if
[ $i -eq 5 ] |
if
((i==5)) |
if
($i==5) |
Sample condition
test |
| fi |
fi |
fi |
endif |
End if statement |
| ulimit |
ulimit |
ulimit |
limit |
Set resource
limits |
| pwd |
pwd |
pwd |
dirs |
Print working
directory |
| read |
read |
read |
$< |
Read from
terminal |
| trap 2 |
trap 2 |
trap 2 |
onintr |
Ignore interrupts |
| |
unalias |
unalias |
unalias |
Remove aliases |
| until |
until |
until |
|
Begin until loop |
| while/do |
while/do |
while/do |
while |
Begin while loop |
The Bourne Again SHell has many more features not listed
here. This table is just to give you an idea of how this shell
incorporates all useful ideas from other shells: there are no
blanks in the column for bash. More
information on features found only in Bash can be retrieved
from the Bash info pages, in the "Bash
Features" section.
More information:
You should at least read one manual, being the manual of
your shell. The preferred choice would be info bash, bash being the
GNU shell and easiest for beginners. Print it out and take it
home, study it whenever you have 5 minutes.
See
Appendix B if you are having
difficulties to assimilate shell commands.
