Date: Sat, 9 Sep 2017 17:38:05 +0100 From: Arthur Chance <freebsd@qeng-ho.org> To: Ernie Luzar <luzar722@gmail.com>, Yuri Pankov <yuripv@gmx.com> Cc: Polytropon <freebsd@edvax.de>, "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org> Subject: Re: script code for end-line Message-ID: <cef84d61-4056-9d17-0d36-0c00de98c76c@qeng-ho.org> In-Reply-To: <59B4087B.2070005@gmail.com> References: <59B332A3.1000205@gmail.com> <20170909030257.d2718c00.freebsd@edvax.de> <c8715d2d-cb1f-592b-7541-a556fa5645a7@gmx.com> <59B4087B.2070005@gmail.com>
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On 09/09/2017 16:27, Ernie Luzar wrote:
> Yuri Pankov wrote:
>> On Sat, 9 Sep 2017 03:02:57 +0200, Polytropon wrote:
>>> On Fri, 08 Sep 2017 20:15:31 -0400, Ernie Luzar wrote:
>>>>
>>>> I have a file that has blank lines with ^M in position one.
>>>>
>>>> I have this if [ "$end-line" = "^M"]; then
>>>>
>>>>
>>>> Is that the correct way to code that between the quotes?
>>>
>>> That will only match the literal string ^M (^ and M).
>>> String evaluation and comparison at this low level
>>> isn't a native skill of sh. There is a way of encoding
>>> characters as octal values, such as \015 for \r, which
>>> equals ^M and 0x0D, but /bin/test (which is [) can only
>>> compare strings.
>>>
>>> Here is a terrible workaround (not tested):
>>>
>>> if [ `echo ${end-line} | od -x | head -n 1 | awk '{ print $2 }'` =
>>> "000d" ]; then
>>> ... do something ...
>>> fi
>>>
>>> Check if there is already a tool for what you're trying
>>> to accomplish (e. g., tr, sed, recode, iconv). ;-)
>>
>> Actually, you can insert real ^M characters and /bin/test should be
>> able to handle them - press ctrl+V ctrl+M.
>> .
>>
>
> I read the man page on the test command and did not come away with the
> syntax to use in a script. An example showing usage inside of the "if"
> statement sure would be more helpful to understand how it works.
As we're talking Bourne shell, "man sh" and look for the $'...' string form.
Dollar-Single Quotes
Enclosing characters between $' and ' preserves the literal mean‐
ing of all characters except backslashes and single quotes. A
backslash introduces a C-style escape sequence:
--
An amusing coincidence: log2(58) = 5.858 (to 0.0003% accuracy).
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