Shell Programming and Scripting

Could you please help me out in letting me know the meaning of

Code:

#!/bin/sh
#!/bin/ksh
#!/bin/bash

what the difference between all these ....

Also please view the below mention script, could you please explain whats this script doing

Code:

#!/bin/bash
t=100
echo $t
echo $tea
echo ${t}ea

Thnkz in advance.

Hello,

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The first line of a script specifies what "language" the script is written in (and should be used to execute what follows).

Code:

#!/bin/sh       - means Bourne shell
#!/bin/ksh      - means Korn shell
#!/bin/bash     - means Bourne Again shell
#!/usr/bin/perl - means Perl

Code:

#!/bin/bash
t=100            - sets a variable called t to 100
echo $t          - prints the value of variable t
echo $tea        - prints the value of variable tea
echo ${t}ea      - prints the value of t followed by the literal characters ea

{ and } are used to separate a variable name from other text - otherwise the shell can't distinguish the variable name from the other text.

Code:

$ cat scott.sh
#!/bin/bash
t=100
echo "\$t ->[$t]"
echo "\$tea ->[$tea]"
tea=foo
echo "\$tea ->[$tea]"
echo "\${t}ea ->[${t}ea]"
$
$ ./scott.sh
$t ->[100]
$tea ->[]
$tea ->[foo]
${t}ea ->[100ea]

I missed out the word "not". But reading it back, the grammer is pretty rubbish too.

Simpler would be
Should have quit while I was ahead.

I should use:
#!/bin/english

I know what I was trying to say, here, but just made a complete mess of it...
So I removed it from the original post.