The Bourne Again Shell. This shell is based on the bourne shell and all of the features and syntax of the Bourne shell work in the BASH shell.
The BASH shell is the standard shell for Linux. Actually when you specify the
Bourne shell, Linux actually uses the BASH shell.
The Korn Shell. The Korn shell, designed at Bell Labs by David Korn, is upward compatible with the Bourne shell. Scripts written for the Bourne should run without modification under the Korn Shell. The Korn Shell provides new capabilities for shell scripts.
A history mechanism with a built-in editor lets you edit and reissue commands. You can also correct your error before you hit return. In order to be in edit mode you must set the -o option like:
set -o viThen when you type commands you can edit them by hitting the escape key.
$ echo hello therr ( hit esc which put the cursor on r) $ echo hello there ( hit r to replace and type e ) $ echo hello there hello there ( the hit reurn and the command is executed)You can edit the recent history by using the j and k keys.
$ history 82 history 83 man ksh 84 man ksh >ksh 85 enscript -G ksh 86 lpq 87 ls 88 alias 89 fc -l 90 exit 91 set -o vi 92 echo hello there 93 history 94 history 95 ls -al 96 ls -alg 97 history $ history ( hit esc the last command appears) $ ls -alg ( k to move up in history file ) $ ls -al ( k to move up in history file ) $ ls -a ( delete the l and return ) . cmkk126.c grepdata lab try1 .. core h.raw letter.c try2 a.out data h2.dat newdata x4key address f2c.c junk nformat.c case format.c k2.dat testl.c $The r command just reissues the last command.
$ r ls -a . cmkk126.c grepdata lab try1 .. core h.raw letter.c try2 a.out data h2.dat newdata x4key address f2c.c junk nformat.c case format.c k2.dat testl.c $
The Korn Shell allows built-in integer arithmetic via the let command.
$ i=3 $ let i=1+1 $ echo $i 2 $ let i=i*3 $ echo $i 6
The Korn shell allows pattern list for file name expansion. Patterns are separated by |.
$ ls a135.t awk2 awk5 awk8 awkb data1 dup junk rmz adata awk3 awk6 awk9 back data2 go level wnames awk1 awk4 awk7 awka data dater guess ow $ l?(pattern-list) matches any one of the given patterns.
$ ls ?(a*|*a) a135.t awk1 awk3 awk5 awk7 awk9 awkb adata awk2 awk4 awk6 awk8 awka data $
An alias feature like the C Shell has been added to the Korn Shell.
$ alias ll='ls -F' $ ll q1 q1mu q2.ans q3 q4 q4.bak q1ans q2 q2.t q3.ans q4.ans $
The Korn shell allows limited arrays and integer type variables.
$ cat ks1
integer k=1
for i
do
x[$k]=$i
let k=k+1
done
let k=k-1
while [ k -gt 0 ]
do
echo ${x[k]}
let k=k-1
done
$
$ ks1 a b c
c
b
a
$
The C Shell. The C shell was developed at UCB by Bill Joy.
Variables are assigned with the set command.
% set now=then % echo $now then
The C shell accepts aliases like the Korn shell.
% alias dir ls -FC % dir ks1* q1ans q2 q2.t q3.ans q4.ans q1 q1mu q2.ans q3 q4 q4.bak
The C shell keeps a command history, that can be edited.
% history
66 vnews -n all
67 ls
68 cd outline/unix
69 histrory
70 history
71 ls -al
72 ls
73 ls -FC
74 ls -a
75 history
I can reissue the last command with !!.
% ls a.out a060 a120 a160 core a010 a070 a130 a170 echo.c a020 a080 a135 a180 eqn a030 a090 a135.t a190 makefile a040 a100 a140 assignments outline a050 a110 a150 class quizes % !! ls a.out a060 a120 a160 core a010 a070 a130 a170 echo.c a020 a080 a135 a180 eqn a030 a090 a135.t a190 makefile a040 a100 a140 assignments outline a050 a110 a150 class quizes
Or I can recall a command by number or by a match.
% !73 ls -FC a.out* a060 a120 a160 core a010 a070 a130 a170 echo.c a020 a080 a135 a180 eqn a030 a090 a135.t a190 makefile a040 a100 a140 assignments/ outline a050 a110 a150 class/ quizes/ % !cd cd outline/unix ~/outline/unix
Commands may be edited when I reissue them
!cd:s/unix/c/ cd outline/c ~/outline/c
Two nice commands of the C shell are pushd and popd. pushd does a cd but remembers the last directory so we can popd back to it.
% pwd /home/kochis/outline/unix % pushd ~/c/utility ~/c/utility ~/outline/unix % pushd ~/outline/c/tests ~/outline/c/tests ~/c/utility ~/outline/unix % popd ~/c/utility ~/outline/unix % popd ~/outline/unix
The C shell allows for integer arithmetic.
% set k=1 % @ k = $k + 2 % echo $k 3
Decision making can be done with the if or switch statements.
The if statement is :
if ( expression)
command
else if (expression)
command
else
command
endif
#!/bin/csh
set month=`date "+%m"`
echo the month number is $month
if ("$month" == 01) then
echo January
else if ("$month" == 02) then
echo February
else if ("$month" == 03) then
echo March
else if ("$month" == 04) then
echo April
else if ("$month" == 05) then
echo May
else if ("$month" == 06) then
echo June
else if ("$month" == 07) then
echo July
else if ("$month" == 08) then
echo August
else if ("$month" == 09) then
echo September
else if ("$month" == 10) then
echo October
else if ("$month" == 11) then
echo November
else
echo December
endif
The switch statement is:
switch (string)
case pattern1 :
command
breaksw
case patternn :
command
breaksw
default :
command
breaksw
endsw
#!/bin/csh
set month=$1
switch ("$month")
case 1 :
echo January
breaksw
case 2 :
echo February
breaksw
case 3 :
echo March
breaksw
case 4 :
echo April
breaksw
case 5 :
echo May
breaksw
case 6 :
echo June
breaksw
case 7 :
echo July
breaksw
case 8 :
echo August
breaksw
case 9 :
echo September
breaksw
case 10:
echo October
breaksw
case 11:
echo November
breaksw
case 12:
echo December
breaksw
default :
echo Bad month number
endsw
The looping constructs for the C shell are: foreach and while.
The foreach command is:
foreach variable (list)
command
end
#!/bin/csh foreach i (`date`) echo $i end
The while command is:
while (expression)
command
end
#!/bin/csh while ( $#argv > 0 ) echo $1 shift end
Like C syntax the while and foreach may use break and continue.
Like C syntax the csh shell supports goto. The syntax is:
goto label label : command