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Replacement of variable by their content in a file

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# 8  
Old 11-05-2016
Actually, this might work as well:
Code:
eval tgtfile=\""$(cat $srcfile)"\"

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dae Don Cragun Scrutinizer
# 9  
Old 11-05-2016
Please be well aware, that using eval you run a risk of executing - potentially malicious - code, e.g. in a "command substitution". Should the srcfile contain a line like $(rm XX), runnig above might perform unwelcome tasks:
Code:
eval tgtfile=\""$(cat $srcfile)"\"
rm: remove regular empty file 'XX'?

Imagine what happened if it were rm /, not aliased to rm -i .
Last edited by RudiC; 11-05-2016 at 12:48 PM..
# 10  
Old 11-06-2016
RudiC,

thanks a lot for that third solution ... I assume that one is better than the previous ones because it is not necessary to use a loop, right ?

I allow myself to ask you a last question (well, two last questions more precisely) regarding your proposal: I am always lost with the "double quote":
  1. why is it necessary to use 2 times "double quote" in that case ?
  2. why is it necessary to protect the outer "double quote" ?

Thanks again to all of your for your time and dedication,

Didier.

---------- Post updated at 09:27 PM ---------- Previous update was at 07:48 PM ----------

RudiC,

just to complete my previous questions in my last post, below an example which is quite difficult to understand for me: using the double-quote two times (with "protection" of the "outer ones") leads the result I want to obtain (this is the syntax you recommend and this is perfect) and deleting the "inner ones" leads to lose the "spaces" and "carriage returns" ...
Too difficult to me ! Smilie

Code:
[x004191a@xsnl11p317a tmp]$ cat dae.txt
DELETE FROM                  CDH_STGN_${ENV1}.T1
;
INSERT INTO                  CDH_STGN_${ENV2}.T2
                            (
                              ...
                            )
;
[x004191a@xsnl11p317a tmp]$ export ENV1=DEV1
[x004191a@xsnl11p317a tmp]$ export ENV2=DEV2
[x004191a@xsnl11p317a tmp]$ eval echo \""$(cat dae.txt)"\"
DELETE FROM                  CDH_STGN_DEV1.T1
;
INSERT INTO                  CDH_STGN_DEV2.T2
                            (
                              ...
                            )
;
[x004191a@xsnl11p317a tmp]$ eval echo \"$(cat dae.txt)\"
DELETE FROM CDH_STGN_DEV1.T1 ; INSERT INTO CDH_STGN_DEV2.T2 ( ... ) ;
[x004191a@xsnl11p317a tmp]$

Last edited by rbatte1; 11-07-2016 at 06:13 AM.. Reason: Converted to formatted number-list
# 11  
Old 11-07-2016
Well, I hope I can explain the behaviour adequately, but mayhap the other experts in here may jump in and correct/improve my comments...

shells, when expanding a line, and IFS is defined as the default chars (space, tab, newline), replace sequences of IFS chars by a single space unless (part of) the line is quoted. Single quotes preserve the string literally (no further expansion) while double quotes allow for expansions inside the string.
Now, eval runs the line through expansion twice. While the unescaped double quotes preserve the line's newline chars et al. in the first run, the escaped ones do so in the second. Escaping keeps them from being paired with the unescaped annihilating the entire effect on the line (i.e. closing the quotation immediately again).

I hope this was not TOO confusing.
This User Gave Thanks to RudiC For This Post:
dae
# 12  
Old 11-07-2016
Thanks a lot RudiC, Smilie ... that was not too confusing but very clear ! Smilie
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