Re: [CentOS] Assitance with perl
On 02/02/2022 11:34 PM, Jon LaBadie wrote:
> On Wed, Feb 02, 2022 at 08:54:38PM -0500, H wrote:
> I am writing a long bash script under CentOS 7 where perl is used for
> manipulating some external files. So far I am using perl one-liners to do
> so but ran into a problem when I need to append text to an external file.
>
> Here is a simplified example in the bash script where txt is a bash
> variable which I built containing a longish text with multiple newlines:
>
> txt="a b$'\n'cd ef$'\n'g h$'\n'ij kl"
>
> A simplified perl one-liner to append the text in the variable above to
> some file in the bash script would be:
>
> perl -pe 'eof && do{print $_'"${txt}"'; exit}' someexternalfile.txt
>
> This works when fine when $txt does /not/ contain any spaces but falls
> apart when it does.
>
> In a shell script why not stick to shell tools?
>
> printf "%s" "${txt}" >> someexternalfile.txt
>
I want to use similar patterns of perl one-liners for more complicated text
substitutions. If I cannot get the simple example above to work, I surely
cannot get more complicated text substitutions, including substitutions
spanning multiple lines, to work.
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Re: [CentOS] Assitance with perl
I avoid using ' or " in one-liners or even programs. I use q() or qq(). These are quote-like operators for single quote and double quote. There are, of course, many more: https://perldoc.perl.org/perlop#Quote-and-Quote-like-Operators gizmo ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Assistance with perl
On 02/03/2022 08:39 AM, Joe Kline wrote:
> I avoid using ' or " in one-liners or even programs.
>
> I use q() or qq().
>
> These are quote-like operators for single quote and double quote.
>
> There are, of course, many more:
>
> https://perldoc.perl.org/perlop#Quote-and-Quote-like-Operators
>
> gizmo
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Thank you, I will look at those (the page says they should be q{} and q{}
rather than q() and q()). It would still be useful for me to understand why my
combination of single and double quotes in the perl command does not work? Just
for "fun" I also tried concatenating the different strings in the perl command
with . which I understand is the perl string concatenation symbol but again to
no avail.
May I ask you what the correct way of including a literal $ in a substitution
string would be? In bash I would precede it with a single \ but that led to
loss of any text after that on that same line when used in the text string I
use in my perl command, neither did preceding it with \\ work.
I have seen that using an ENV() construct would work but I would prefer
something simpler, if at all possible.
I have used literal # in my substitution string without any problems but have
not gotten literal $ to work.
Thanks.
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[CentOS] EPEL repo RPM in CentOS 9-stream?
Will the Fedora EPEL repo RPM be added to any CentOS 9-stream core repos, like epel-release is in 7 and 8-stream extras? -- Chris Adams ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Assistance with perl
On 2/3/22 09:21, H wrote:
On 02/03/2022 08:39 AM, Joe Kline wrote:
I avoid using ' or " in one-liners or even programs.
I use q() or qq().
These are quote-like operators for single quote and double quote.
There are, of course, many more:
https://perldoc.perl.org/perlop#Quote-and-Quote-like-Operators
gizmo
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Thank you, I will look at those (the page says they should be q{} and q{} rather than q()
and q()). It would still be useful for me to understand why my combination of single and
double quotes in the perl command does not work? Just for "fun" I also tried
concatenating the different strings in the perl command with . which I understand is the
perl string concatenation symbol but again to no avail.
May I ask you what the correct way of including a literal $ in a substitution
string would be? In bash I would precede it with a single \ but that led to
loss of any text after that on that same line when used in the text string I
use in my perl command, neither did preceding it with \\ work.
I have seen that using an ENV() construct would work but I would prefer
something simpler, if at all possible.
I have used literal # in my substitution string without any problems but have
not gotten literal $ to work.
I think it's been pointed out that it might be a lot easier to stick
with either perl or shell.
For shell you could probably do:
( cat - ; echo $txt ) >output
As for perl, I guess I'll leave that as an exercise for you how to
translate from shell to perl.
For the quote-like operators you can use either () or {} for the
delimiter for almost all of the quote-like operators, in fact, from the doc:
"In the following table, a {} represents any pair of delimiters you choose."
gizmo
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