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# 1  
Old 09-13-2011
Java Variable


Hi !

can anyone explain what does mean by the above expressions

i mean why double quotes has been used along with dot and dollar sign?


Last edited by vbe; 09-13-2011 at 10:43 AM.. Reason: Please use code tags for any code or data
# 2  
Old 09-13-2011
I don't see a reason - you could try just without and will have the same output. Looks like somebody wanted to define some temporary file names. The $$ will contain the process id (PID) of the shell the script is being executed in. Every time the script is started anew, the PID will be different.
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# 3  
Old 09-13-2011
If you were parano´d you would do such thing to be sure to affect a string (between the double quotes...) dot PID to a variable...Smilie
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# 4  
Old 09-13-2011
tmpf0=temp0.$$ tmpf1=temp1.$$ tmpf2=temp2.$$

tmpf0="temp0".$$ tmpf1="temp1".$$ tmpf2="temp2".$$

it means both will produce same results?

and why to include dot(.) between temp0 and $$ (temp0.$$)

and can you explain to me why we include the following line at top of every file?


and kindly explain at low level because i'm new to shell scripting otherwise i would have not asked such trivial questions.

Thanks in advance
# 5  
Old 09-13-2011
it means both will produce same results?
Why not try it?

echo temp1.$$
echo "temp1".$$

and why to include dot(.) between temp0 and $$ (temp0.$$)

No particular reason. It's just a randomly generated file name.
and can you explain to me why we include the following line at top of every file?

So that when the script is run, it uses /bin/sh to process it. A PERL script might use #!/usr/bin/perl. If you do sh ./script it should effectively run it the same way without a #! being necessary but if you want the script to be capable of running all by itself, the #! line is a good idea.
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# 6  
Old 09-14-2011

thank you corona688 i was looking for such an answer...

Kind Regards,


---------- Post updated at 08:28 AM ---------- Previous update was at 02:42 AM ----------

well Corona i understood your point but it is not exactly as you said "courtesy"

for example if i run the code with out including #!/bin/sh it also work so why to include it? the following code is working fine whether i include #!/bin/sh at the top or not


result=`expr $value1 + $value2`
echo $value1 + $value2 = $result

i hope you have understood my point now
# 7  
Old 09-14-2011
Originally Posted by ourned
well Corona i understood your point but it is not exactly as you said "courtesy"

for example if i run the code with out including #!/bin/sh it also work so why to include it?
Without the #!, the OS will assume the default, /bin/sh.

But a UNIX system may have many languages available. If a script needs /bin/bash, /bin/ksh, /bin/csh, /bin/zsh, /usr/bin/perl, /usr/bin/awk, or anything else, it can put it after #! and run the script using that instead.

It's traditional to put #!/bin/sh up top even for scripts which don't need it. This is safer -- it's not impossible that a programmer might write a comment with #!, which would mess up the script if it didn't have #!/bin/sh first. If there's weird characters at the end of the line, having a #! will cause it to quit with 'bad interpreter' (since it can't find the filename /bin/sh^M) instead of trying to run invalid code inside a valid shell. It also lets a human instantly tell scripts apart from plain text files.
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