I need to include /& in a ZPL string to break up a long line on a label.
There is a stackoverflow post that suggests a lot of methods but does not seem to answer my question:
Here is my problem:
>>"asdf & asdf".gsub("&", "\\\\&")
=>"asdf \\& asdf"
Yes, if I puts the string it will return what I want:
>>puts "asdf & asdf".gsub("&", "\\\\&")
=>asdf \& asdf
But I need the actual string to equal asdf \& asdf
I've tried inspect:
>>"asdf & asdf".gsub("&", "\\\\&").inspect
=>"\"asdf \\\\& asdf\""
>>"asdf & asdf".gsub("&", "\&").inspect
=>"\"asdf & asdf\""
But that also does not return what I need. Maybe there is some combination that I'm missing that will return a \& in the string?
Thanks
When you see Ruby showing something like:
"asdf \\& asdf"
That's broken up into the tokens \\ (backslash) and & (ampersand) where the first backslash is special, the second is an actual character. You can read this as "literal backslash".
When printed you're seeing the actual string. It's correct.
Internally the double backslashes aren't actually there, it's just a consequence of how double-quoted strings must be handled.
This is to ensure that \n and \r and other control characters work, but you're also able to put in actual backslashes. There's a big difference between \n (newline) and \\n (literal backslash letter n).
You'll see this often when dealing with data formats that have special characters. For example, in printf style formatters % is significant, so to print an actual % you need to double it up:
'%.1f%%' % 10.3
#=> "10.3%"
Each format will have its own quirks and concerns. HTML doesn't treat backslash as special, but it does < and > and &, so you'll see & instead of ampersand.
Related
In C#, there is a verbatim string so that,
string c = "hello \t world"; // hello world
string d = #"hello \t world"; // hello \t world
I am new to shell script, is there a similar method in shell?
Because I have many folders with the name like "Apparel & Accessories > Clothing > Activewear", I want to know if there is a easy way to process the escape characters without write so many .
test.sh
director="Apparel & Accessories > Clothing > Activewear"
# any action to escape spaces, &, > ???
hadoop fs -ls $director
For definining the specific string in your example, Apparel & Accessories > Clothing > Activewear, either double quotes or single quotes will work; referring to it later is a different story, however:
In the shell (any POSIX-compatible shell), how you refer to a variable is just as important as how you define it.
To safely refer to a previously defined variable without side-effects, enclose it in double quotes, e.g., "$directory".
To define [a variable as] a literal (verbatim) string:
(By contrast, to define a variable with embedded variable references or embedded command substitutions or embedded arithmetic expressions, use double quotes (").)
If your string contains NO single quotes:
Use a single-quoted string, e.g.:
directory='Apparel & Accessories > Clothing > Activewear'
A single-quoted string is not subject to any interpretation by the shell, so it's generally the safest option for defining a literal. Note that the string may span multiple lines; e.g.:
multiline='line 1
line 2'
If your string DOES contain single quotes (e.g., I'm here.) and you want a solution that works in all POSIX-compatible shells:
Break the string into multiple (single-quoted) parts and splice in single-quote characters:
Note: Sadly, single-quoted strings cannot contain single quotes, not even with escaping.
directory='I'\''m here.'
The string is broken into into single-quoted I, followed by literal ' (escaped as an unquoted string as \'), followed by single-quoted m here.. By virtue of having NO spaces between the parts, the result is a single string containing a literal single quote after I.
Alternative: if you don't mind using a multiline statement, you can use a quoted here document, as described at the bottom.
If your string DOES contain single quotes (e.g., I'm here.) and you want a solution that works in bash, ksh, and zsh:
Use ANSI-C quoting:
directory=$'I\'m here.'
Note: As you can see, ANSI-C quoting allows for escaping single quotes as \', but note the additional implications: other \<char> sequences are subject to interpretation, too; e.g., \n is interpreted as a newline character - see http://www.gnu.org/software/bash/manual/bash.html#ANSI_002dC-Quoting
Tip of the hat to #chepner, who points out that the POSIX-compatible way of directly including a single quote in a string to be used verbatim is to use read -r with a here document using a quoted opening delimiter (the -r option ensures that \ characters in the string are treated as literals).
# *Any* form of quoting, not just single quotes, on the opening EOF will work.
# Note that $HOME will by design NOT be expanded.
# (If you didn't quote the opening EOF, it would.)
read -r directory <<'EOF'
I'm here at $HOME
EOF
Note that here documents create stdin input (which read reads in this case). Therefore, you cannot use this technique to directly pass the resulting string as an argument.
use strong quotes i.e. 'string', allowing escape char or special char for string.
e.g. declare director='Apparel & Accessories > Clothing > Activewear'
also using declare is a good practice while declaring variable.
These \\n are showing up in my strings even though it should only be \n.
But if I do this :
"\n".gsub('\\n','\b')
It returns :
"\n"
Ideally, I'm trying to find a regex that could rewrite this string :
"R3pQvDqmz/EQ7zho2mhIeE6UB4dLa6GUH7173VEMdGCcdsRm5pernkqCgbnj\\nZjTX\\n"
To not display two backslashes, but just one like this :
"R3pQvDqmz/EQ7zho2mhIeE6UB4dLa6GUH7173VEMdGCcdsRm5pernkqCgbnj\nZjTX\n"
But any of the regex I do will not work. I can gsub out the \n and put something like X there, but if I put a \ in it, then Ruby escapes it with an additional \ which consequentially destroys my encryption module as it needs to be specific.
Any ideas?
You are falling into the trap of a different meaning of escapes when used in strings with double quotes vs single quotes. Double-quoted strings allow escape characters to be used. Thus, here "\n" actually is a one-character string containing a single line feed. Compare that to '\n' which is a two-character string containing a literal backslash followed by a character n.
This explains, whey your gsub doesn't match. If you use the following code, it should work:
"\\n".gsub('\n','\b')
For your actual issue, you can use this
string = "R3pQvDqmz/EQ7zho2mhIeE6UB4dLa6GUH7173VEMdGCcdsRm5pernkqCgbnj\\nZjTX\\n"
new_string = string.gsub("\\n", "\n")
I am trying to get the directory of a file on a Windows box using File.dirname. I get the file ("file1" below) from the Windows box and return it to my the Mac OS X box that the script is run on.
file1 = "C:\Administrator\proj1\testFile.txt" below is to simplify my example, however, to make it more clear, I am getting this value from a remote box and returning it to my development box:
file1 = "C:\Administrator\proj1\testFile.txt"
path = "#{File.dirname(file1)}"
puts "#{path}"
>> .
I am confused on why it would return '.'. I saw on ruby-doc.org that File.dirname says the following:
"Returns all components of the filename given in file_name except the last one. The filename can be formed using both File::SEPARATOR and File::ALT_SEPARETOR as the separator when File::ALT_SEPARATOR is not nil."
I did a puts on File::SEPARATOR and File::ALT_SEPARATOR and got the following:
File::SEPARATOR >> /
File::ALT_SEPARATOR >>
I assumed it was because "\" wasn't a valid file separator. So I set File::ALT_SEPARATOR to "\". However, even after that, I still got the same value when I puts path.
I tried using File.realdirpath and this was the result:
file1 = "C:\Administrator\proj1\testFile.txt"
path = "#{File.realdirpath(file1)}"
puts "{path}"
>> /Users/me/myProject/C:\Administrator\proj1\testFile.txt
It seemed to add the path from where I called the Ruby script and appended the full path (including the file name). Seems to be odd behavior.
Any ideas, comments or suggestions would be great.
The problem is that when you declare file1, those backslashes define escape characters. Notice the return:
file1 = "C:\Administrator\proj1\testFile.txt"
=> "C:Administratorproj1\testFile.txt"
If you want to store a filepath in a string, you either need to use forward slashes or double backslashes (to escape the escape character):
file1 = "C:\\Administrator\\proj1\\testFile.txt"
file1 = "C:/Administrator/proj1/testFile.txt"
Okay, I was able to duplicate this problem as well.
As #fbonetti pointed out, you have to enclose your directory with single quotes to keep ruby from interpreting the backslashes as escapes, so start with that...
>> file1='C:\Administrator\proj1\testFile.txt'
=> "C:\\Administrator\\proj1\\testFile.txt"
Then, passing file1 through gsub to 'normalize' the slashes, gives you the results you're expecting.
>> File.dirname(file1.gsub('\\', '/'))
=> "C:/Administrator/proj1"
Of course, you could always reverse the gsub if you needed them to be backslashes again.
>> File.dirname(file1.gsub('\\', '/')).gsub('/', '\\')
=> "C:\\Administrator\\proj1"
I figured it out. It was an issue with the version of Ruby I was using. I was using ruby 1.9.3 and then I switched to jruby 1.7.3 and it works correctly now.
Ruby's IO documentation is of great help when dealing with different OS path separators. From the documentation:
Ruby will convert pathnames between different operating system conventions if possible. For instance, on a Windows system the filename "/gumby/ruby/test.rb" will be opened as "\gumby\ruby\test.rb". When specifying a Windows-style filename in a Ruby string, remember to escape the backslashes:
"c:\\gumby\\ruby\\test.rb"
Our examples here will use the Unix-style forward slashes; File::ALT_SEPARATOR can be used to get the platform-specific separator character.
So, in other words, you don't need to hassle with backslashes, and whether you need to use single or double-quotes. Keep it simple, and use forward-slashes and let Ruby worry about it. That way your code is portable across *nix/Mac OS and Windows.
Beyond that, it looks like there's a real need to learn how character escaping works in double-quoted strings vs. single-quoted strings. This is from "Programming Ruby":
Ruby provides a number of mechanisms for creating literal strings. Each generates objects of type String. The different mechanisms vary in terms of how a string is delimited and how much substitution is done on the literal's content.
Single-quoted string literals (' stuff ' and %q/stuff/) undergo the least substitution. Both convert the sequence into a single backslash, and the form with single quotes converts \' into a single quote.
'hello' » hello
'a backslash \'\\\'' » a backslash '\'
%q/simple string/ » simple string
%q(nesting (really) works) » nesting (really) works
%q no_blanks_here ; » no_blanks_here
Double-quoted strings ("stuff", %Q/stuff/, and %/stuff/) undergo additional substitutions, shown in Table 18.2 on page 203.
Substitutions in double-quoted strings
\\a Bell/alert (0x07) \\nnn Octal nnn
\\b Backspace (0x08) \\xnn Hex nn
\\e Escape (0x1b) \\cx Control-x
\\f Formfeed (0x0c) \\C-x Control-x
\\n Newline (0x0a) \\M-x Meta-x
\\r Return (0x0d) \\M-\\C-x Meta-control-x
\\s Space (0x20) \\x x
\\t Tab (0x09) #{expr} Value of expr
\\v Vertical tab (0x0b)
a = 123
"\123mile" » Smile
"Say \"Hello\"" » Say "Hello"
%Q!"I said 'nuts'," I said! » "I said 'nuts'," I said
%Q{Try #{a + 1}, not #{a - 1}} » Try 124, not 122
%<Try #{a + 1}, not #{a - 1}> » Try 124, not 122
"Try #{a + 1}, not #{a - 1}" » Try 124, not 122
Hi I need to create string like this:
drawtext="fontfile=/Users/stpn/Documents/Video_Experiments/fonts/Trebuchet_MS.ttf:text='content':fontsize=100:fontcolor=red:y=h/2"
I want to do something like
str = Q%[drawtext="fontfile=/Users/stpn/Documents/Video_Experiments/fonts/Trebuchet_MS.ttf:text='content':fontsize=100:fontcolor=red:y=h/2"]
I am getting this:
=> "drawtext=\"fontfile=/Users/stpn/Documents/Video_Experiments/fonts/Trebuchet_MS.ttf:text='content':fontsize=100:fontcolor=red:y=h/2\""
The escape characters after equals sign in drawtext=" is what I want to get rid of.. How to achieve that?
The string is to be used in a command line args.
Like many languages, Ruby needs a way of delimiting a quoted quote, and the enclosing quotes.
What you're seeing is the escape character which is a way of saying literal quote instead of syntactic quote:
foo = 'test="test"'
# => "test=\"test\""
The escape character is only there because double-quotes are used by default when inspecting a string. It's stored internally as a single character, of course. You may also see these in other circumstances such as a CR+LF delimited file line:
"example_line\r\n"
The \r and \n here correspond with carriage-return and line-feed characters. There's several of these characters defined in ANSI C that have carried over into many languages including Ruby and JavaScript.
When you output a string those escape characters are not displayed:
puts foo
test="test"
I am trying to write a regex in Ruby to test a string such as:
"GET \"anything/here.txt\""
the point is, everything can be in the outer double quote, but all double quotes in the outer double quotes must be escaped by back slash(otherwise it doesnt match). So for example
"GET "anything/here.txt""
this will not be a proper line.
I tried many ways to write the regex but doest work. can anyone help me with this? thank you
You can use positive lookbehind:
/\A"((?<=\\)"|[^"])*"\z/
This does exactly what you asked for: "if a double quote appears inside the outer double quotes without a backslash prefixed, it doesn't match."
Some comments:
\A,\z: These match only at the beginning and end of the string. So the pattern has to match against the whole string, not a part of it.
(?<=): This is the syntax for positive lookbehind; it asserts that a pattern must match directly before the current position. So (?<=\\)" matches "a double quote which is preceded by a backslash".
[^"]: This matches "any character which is not a backslash".
One point about this regex, is that it will match an inner double quote which is preceded by two backslashes. If that is a problem, post a comment and I'll fix it.
If your version of Ruby doesn't have lookbehind, you could do something like:
/\A"(\\.|[^"\\])*"\z/
Note that unlike the first regexp, this one does not count a double backslash as escaping a quote (rather, the first backslash escapes the second one), so "\\"" will not match.
This works:
/"(?<method>[A-Z]*)\s*\\\"(?<file>[^\\"]*)\\""/
See it on Rubular.
Edit:
"(?<method>[A-Z]*)\s(?<content>(\\\"|[a-z\/\.]*)*)"
See it here.
Edit 2: without (? ...) sequence (for Ruby 1.8.6):
"([A-Z]*)\s((\\\"|[a-z\/\.]*)*)"
Rubular here.
Tested this on Rubular successfully:
\"GET \\\".*\\\"\"
Breakdown:
\" - Escape the " for the regex string, meaning the literal character "
GET - Assuming you just want GET than this is explicit
\\" - Escape \ and " to get the literal string \"
.* - 0 or more of any character other than \n
\\"\" - Escapes for the literal \""
I'm not sure a regex is really your best tool here, but if you insist on using one, I recommend thinking of the string as a sequence of tokens: a quote, then a series of things that are either \\, \" or anything that isn't a quote, then a closing quote at the end. So this:
^"(\\\\|\\"|[^"])*"$