I'm stuck and hope someone can help. I am trying to use the tr command to capitalize the text of first two columns of a file but can't seem to figure it out. It's actually for an assignment for a class I am taking and I must use tr. Can anyone help?
Thanks in advance
This is a comprehensive guide/explanation to using tr
Reference: http://www.thegeekstuff.com/2012/12/linux-tr-command/
The general syntax of tr is
tr [options] set1 [set2]
The items in the square brackets are optional. tr requires at least one argument and accepts a maximum of two. The first, designated set1, lists the characters in the text to be replaced or removed. The second, set2, lists the characters that are to be substituted for the characters listed in the first argument.
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I want to search a file for a specific string and then place a comment at the beginning of that string. But I need an answer that avoids regex, global changes, and all the other fancy stuff.
I wrote this line:
sed -i.bak '/PermitRootLogin no/# PermitRootLogin no/' ./sshd_config
but I get an error:
sed: -e expression #1, char 21: comments don't accept any addresses
I assume the issue is that I need to escape the # character, but I'm not finding any resources on how to do that, or even mentioning it. I've tried various combinations of putting ^ or \ or \^ in front of the # but I'm jut not getting it right.
Please note I am intentionally repeating the text to be replaced. I would like the most simple possible solution to this question: how to replace "XYX" with "# XYZ" in the most obvious possible way.
As indicated in the comments by #mlt , you could try adding an s at the beginning your sed command. Straight from his comment:
s/PermitRootLogin....
I see that you said you're intentionally repeating the test to be replaced. If by that you mean, you want it to be the same, maybe consider grouping your matched text. I understand you may have meant that you just want it hand typed. Anyway, here is how to match the grouped text and add the comment character:
s/(PermitRootLogin)/# \1/
The parens indicated that the matched text should be consider a group, the \1 indicates that you want to put that matched group there.
I hope this was helpful. Happy coding! Leave a comment if you have any questions.
I am building some tables in org-mode and I need to enter "||" into the table (for the logical OR command) and nothing I try turns the two characters off as table constructors.
I've tried single quotes, double quotes, backticks and prefacing them with '\'. I've also tried every permutation of using ':=' to get a literal string and they don't work.
// Tony Williams
Depending on what you want to do with the output of the table, you could use alternative unicode characters that look like vertical pipes (or double vertical pipes). Examples:
This is the pipe character written twice (as for logical OR):
||
Those are similar (or not too different) looking unicode characters
‖ - ¦¦ - ❘❘
Of course, this won't work for you if you are not just interested in the looks (but escaping pipes would not work either).
See here more unicode characters you might like better than those 3 above
It turns out that you can use HTML entities in org-mode tables for output via pandoc.
\vert{} doesn't work but I went to the table pointed to by MrSpock and tried the HTML entity and the output when run through pandoc was perfect. || gives me '||'. I also tested a few other HTML entities and they also worked fine.
Well, if the goal is to export your notes, then
$\lvert\mathbb{N}\rvert$
would be an equivalent of
$|\mathbb{N}|$
Character is: \vert
Example: a \vert\ b -> a | b
I'm looking for a way to replace all instances of a form:
model->variable
with
models[variable][index]
where variable can be pretty much any combination of letters and numbers, probably defined like [0-9a-Z]{4,12}.
There are hundreds of such variables in the text. I need to know exact form of found string "variable" to use it in replacement. Is there a way to "remember" the string and use it later? Or any other method / software which could help in such case?
Thanks in advance.
If you could convert "variable" to uppercase by the way, it would be awesome.
You can use things in the pattern to replace with if you enclose it in \(...\). You then use \1 to insert the thing that was captured by the first such bracket.
A naïve solution to your problem would be this:
sed 's/model->\(.*\)/models[\1][index]/' file.txt
Imagine I have a file that has the following type of line:
FIXED_DATA1 VARIABLE_DATA FIXED_DATA2
I want to change the fixed data and leave the variable data as is. For various reasons, using two sed operations to replace the fixed data will not work. For instance, the fixed fields might be double-quotes, and the line has other areas containing them, thus really the regex is written to match a pattern in the variable data and the fixed data.
If I'm bent on using sed, is there a way to change both fixed data fields at once while leaving the variable field unchanged?
Thanks.
You need to partition the line into the three pieces, replace the outer two and leave the middle alone:
sed 's/^FIX1 \(.*\) FIX2$/New \1 End/'
You can make the beginning and end matches more complex as needed.
I have an NSArray of lines (objective-c iphone), and I'm trying to find the line which starts with a number, followed by a dot and a space, but can have any number of spaces (including none) before it, and have any text following it eg:
1. random text
2. text random
3.
what regular expression would I use to get this? (I'm trying to learn it, and I needed the above expression anyway, so I thought I'd use it as an example)
With C#:
#"^ *[0-9]+\. "
It doesn't check for the presence of something after the ., so this is legal:
1.(space)
If you delete the # and escape the \ it should work with other languages (it is pretty "down-to-earth" as RegExpes go)
I may suggest (Perl-compatible regexp):
^\s*\d+\.\s
At the beginning of a line:
Any number (0-n) of spaces
One or more digits
A dot
A space
Something like
^\s*\d+\.
But it depends on the language.
/^\s*[0-9]+\.\s+/
would be my guess providing you don't have any space before the number