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] 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
On 1/30/22 17:12, 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.
I would like to keep the above structure, ie using bash variables to build text strings
and one-liners to do the text manipulation. Hopefully there is a "simple"
solution to do this, I have tried many variations and failed miserably... Note that I
also want to use a similar pattern to do substitutions in external files, I would thus
like to use the same code pattern.
Thanks.
On 2/2/22 17:54, H wrote:
> I am still having a problem. The following (where $txt is an
arbitrary string) works:
>
> perl -e 'print '"\"${txt}\""';'
>
> The following does not work (I want to append the content of the $txt
to the end of an existing file in-place):
>
> perl -i -pe 'eof && do{print $_''\"aaa\"''; exit}' somefile.txt
>
> but this does:
>
> perl -i -pe "eof && do{print $_""\"${txt}\""'; exit}' somefile.txt
>
> as does:
>
> perl -i -pe "eof && do{print $_""\"${txt}\"""; exit}" somefile.txt
>
> The difference is that the last two perl command strings use " rather
than '.
>
> My questions are:
>
> - Why would not using single-quotes for parts of the perl command
string work?
>
> - Is there any reason I should fight this or should I just go with
double-quotes for all parts of the perl command string? Any downside?
Remember, these are all in bash scripts and I am looking for a "pattern"
to use for other, more complicated text substitutions, hence the use of
perl.
On 2/2/22 18:55, H wrote:
> I see I made a mistake, the line:
>
> perl -i -pe 'eof && do{print $_''\"aaa\"''; exit}' somefile.txt
>
> should be:
>
> perl -i -pe 'eof && do{print $_''\"${txt}\"''; exit}' somefile.txt
>
> Related question, if the $txt string contains eg $ or another special
character, what would be the best way of escaping it so it is not
substituted by perl?
AIUI you are looking for a Bash shell scripting (programming) technique
that allows you to append content to a file using a Perl one-liner with
data that is dynamically generated from Bash variable values, all inside
a Bash script (?).
Perhaps it would be simpler if you put the data into a file and then
invoked the Perl one-liner with the data file filename as an argument:
2022-02-02 22:08:34 dpchrist@tinkywinky ~
$ cat somefile.txt
this is the contents of somefile.
some more contents.
2022-02-02 22:08:37 dpchrist@tinkywinky ~
$ cat centos-h.sh
#!/bin/bash
txt="... foo ..."
echo "$txt" > tmp.txt
perl -pe 's/foo/bar/g' tmp.txt >> somefile.txt
2022-02-02 22:08:46 dpchrist@tinkywinky ~
$ bash centos-h.sh
2022-02-02 22:08:53 dpchrist@tinkywinky ~
$ cat somefile.txt
this is the contents of somefile.
some more contents.
... bar ...
David
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Re: [CentOS] Assitance with perl
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
--
Jon H. LaBadie j...@labadie.us
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Re: [CentOS] Assitance with perl
On 02/02/2022 08:54 PM, H wrote:
> On 01/31/2022 09:59 PM, H wrote:
>> On 01/30/2022 11:00 PM, Orion Poplawski wrote:
>>> On 1/30/22 18:12, 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.
I would like to keep the above structure, ie using bash variables to build
text strings and one-liners to do the text manipulation. Hopefully there
is a "simple" solution to do this, I have tried many variations and failed
miserably... Note that I also want to use a similar pattern to do
substitutions in external files, I would thus like to use the same code
pattern.
>>> I don't understand why:
>>>
>>> echo -e $txt >> someexternalfile.txt
>>>
>>> doesn't do what you want, or if perl is absolutely what you need:
>>>
>>> perl -e "print \"${txt}\";" >> someexternalfile.txt
>>>
>>> I have no idea if you are trying to output literal $'s or 's or not.
>>>
>> Thank you, it works! I had forgotten to escape the quotes around my bash
>> variable...
>>
> I am still having a problem. The following (where $txt is an arbitrary
> string) works:
>
> perl -e 'print '"\"${txt}\""';'
>
> The following does not work (I want to append the content of the $txt to the
> end of an existing file in-place):
>
> perl -i -pe 'eof && do{print $_''\"aaa\"''; exit}' somefile.txt
>
> but this does:
>
> perl -i -pe "eof && do{print $_""\"${txt}\""'; exit}' somefile.txt
>
> as does:
>
> perl -i -pe "eof && do{print $_""\"${txt}\"""; exit}" somefile.txt
>
> The difference is that the last two perl command strings use " rather than '.
>
> My questions are:
>
> - Why would not using single-quotes for parts of the perl command string work?
>
> - Is there any reason I should fight this or should I just go with
> double-quotes for all parts of the perl command string? Any downside?
> Remember, these are all in bash scripts and I am looking for a "pattern" to
> use for other, more complicated text substitutions, hence the use of perl.
>
> Thank you!
>
I see I made a mistake, the line:
perl -i -pe 'eof && do{print $_''\"aaa\"''; exit}' somefile.txt
should be:
perl -i -pe 'eof && do{print $_''\"${txt}\"''; exit}' somefile.txt
Related question, if the $txt string contains eg $ or another special
character, what would be the best way of escaping it so it is not substituted
by perl?
Thank you.
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Re: [CentOS] Assitance with perl
On 01/31/2022 09:59 PM, H wrote:
> On 01/30/2022 11:00 PM, Orion Poplawski wrote:
>> On 1/30/22 18:12, 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.
>>>
>>> I would like to keep the above structure, ie using bash variables to build
>>> text strings and one-liners to do the text manipulation. Hopefully there is
>>> a "simple" solution to do this, I have tried many variations and failed
>>> miserably... Note that I also want to use a similar pattern to do
>>> substitutions in external files, I would thus like to use the same code
>>> pattern.
>> I don't understand why:
>>
>> echo -e $txt >> someexternalfile.txt
>>
>> doesn't do what you want, or if perl is absolutely what you need:
>>
>> perl -e "print \"${txt}\";" >> someexternalfile.txt
>>
>> I have no idea if you are trying to output literal $'s or 's or not.
>>
> Thank you, it works! I had forgotten to escape the quotes around my bash
> variable...
>
I am still having a problem. The following (where $txt is an arbitrary string)
works:
perl -e 'print '"\"${txt}\""';'
The following does not work (I want to append the content of the $txt to the
end of an existing file in-place):
perl -i -pe 'eof && do{print $_''\"aaa\"''; exit}' somefile.txt
but this does:
perl -i -pe "eof && do{print $_""\"${txt}\""'; exit}' somefile.txt
as does:
perl -i -pe "eof && do{print $_""\"${txt}\"""; exit}" somefile.txt
The difference is that the last two perl command strings use " rather than '.
My questions are:
- Why would not using single-quotes for parts of the perl command string work?
- Is there any reason I should fight this or should I just go with
double-quotes for all parts of the perl command string? Any downside? Remember,
these are all in bash scripts and I am looking for a "pattern" to use for
other, more complicated text substitutions, hence the use of perl.
Thank you!
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Re: [CentOS] Assitance with perl
On 01/30/2022 11:00 PM, Orion Poplawski wrote:
> On 1/30/22 18:12, 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.
>>
>> I would like to keep the above structure, ie using bash variables to build
>> text strings and one-liners to do the text manipulation. Hopefully there is
>> a "simple" solution to do this, I have tried many variations and failed
>> miserably... Note that I also want to use a similar pattern to do
>> substitutions in external files, I would thus like to use the same code
>> pattern.
>
> I don't understand why:
>
> echo -e $txt >> someexternalfile.txt
>
> doesn't do what you want, or if perl is absolutely what you need:
>
> perl -e "print \"${txt}\";" >> someexternalfile.txt
>
> I have no idea if you are trying to output literal $'s or 's or not.
>
Thank you, it works! I had forgotten to escape the quotes around my bash
variable...
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Re: [CentOS] Assitance with perl
On 1/30/22 18:12, H wrote:
I am writing a long bash script under CentOS 7 where perl is used for
manipulating some external files. So far I am using perl one-liners to do so
but ran into a problem when I need to append text to an external file.
Here is a simplified example in the bash script where txt is a bash variable
which I built containing a longish text with multiple newlines:
txt="a b$'\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.
I would like to keep the above structure, ie using bash variables to build text strings
and one-liners to do the text manipulation. Hopefully there is a "simple"
solution to do this, I have tried many variations and failed miserably... Note that I
also want to use a similar pattern to do substitutions in external files, I would thus
like to use the same code pattern.
I don't understand why:
echo -e $txt >> someexternalfile.txt
doesn't do what you want, or if perl is absolutely what you need:
perl -e "print \"${txt}\";" >> someexternalfile.txt
I have no idea if you are trying to output literal $'s or 's or not.
--
Orion Poplawski
he/him/his - surely the least important thing about me
Manager of NWRA Technical Systems 720-772-5637
NWRA, Boulder/CoRA Office FAX: 303-415-9702
3380 Mitchell Lane or...@nwra.com
Boulder, CO 80301 https://www.nwra.com/
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Re: [CentOS] Assitance with perl
On January 30, 2022 8:25:46 PM EST, mailist wrote: >On 2022-01-30 20:12, 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. > >Rewrite the whole thing in Perl. Over the years, I have rewritten >scores of bash scripts >in Perl, and they 1. execute much faster, 2. don't lose variables from >while loops, >3. can use any of the thousands of CPAN modules, 4. can use libraries, >and on and on. > >Todd Merriman >Software Toolz >___ >CentOS mailing list >CentOS@centos.org >https://lists.centos.org/mailman/listinfo/centos Sorry but not in the plans. Not needed. ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Assitance with perl
On 2022-01-30 20:12, 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. Rewrite the whole thing in Perl. Over the years, I have rewritten scores of bash scripts in Perl, and they 1. execute much faster, 2. don't lose variables from while loops, 3. can use any of the thousands of CPAN modules, 4. can use libraries, and on and on. Todd Merriman Software Toolz ___ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
[CentOS] Assitance with perl
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.
I would like to keep the above structure, ie using bash variables to build text
strings and one-liners to do the text manipulation. Hopefully there is a
"simple" solution to do this, I have tried many variations and failed
miserably... Note that I also want to use a similar pattern to do substitutions
in external files, I would thus like to use the same code pattern.
Thanks.
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