help me out in letting me know the meaning of sh, ksh, bash

jojo123 · #1 (**permalink**) 07-04-2009

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.

Neo · #2 (**permalink**) 07-04-2009

Hello,

Per our forum rules, all threads must have a descriptive subject text. For example, do not post questions with subjects like "Help Me!", "Urgent!!" or "Doubt". Post subjects like "Execution Problems with Cron" or "Help with Backup Shell Script".

The reason for this is that nearly 95% of all visitors to this site come here because they are referred by a search engine. In order for future searches on your post (with answers) to work well, the subject field must be something useful and related to the problem!

In addition, current forum users who are kind enough to answer questions should be able to understand the essence of your query at first glance.

So, as a benefit and courtesy to current and future knowledge seekers, please be careful with your subject text. You might receive a forum infraction if you don't pay attention to this.

Thank you.

The UNIX and Linux Forums

scottn · #3 (**permalink**) 07-04-2009

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.

vgersh99 · #4 (**permalink**) 07-04-2009

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]

scottn · #5 (**permalink**) 07-04-2009

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

Simpler would be

Quote:

${t}ea is not the same as $tea

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...

Quote:

If you set a variable called "tea" to 100, then ${t}ea and $tea would not mean the same thing, but if your intention was to add ea to $t, then you need the { }.

So I removed it from the original post.

More UNIX and Linux Forum Topics You Might Find Helpful
Thread	Thread Starter	Forum	Replies	Last Post
meaning of ${0%${0##*/}}	nyelavarthy	AIX	7	09-23-2008 02:48 AM
if [ ! -r ${1} ] meaning in ksh	naveeng.81	Shell Programming and Scripting	1	04-09-2008 01:47 PM
OopenSSH not letting me in!	BG_JrAdmin	SUN Solaris	2	09-12-2006 11:54 AM
what is the meaning here?	forevercalz	Shell Programming and Scripting	2	09-29-2005 12:46 PM
client app not letting go of socket	fusion99	UNIX for Dummies Questions & Answers	1	02-20-2004 10:13 AM

Bits Awarded / Charged to jojo123 for this Post
Date	User	Comment	Amount
07-04-2009	Neo	changed title, added code tags.... do it yourself per rules.	-15,000

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes	Rate This Thread
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode	Rate This Thread: