How do I create a raw String literal that contains quotes?
Documentation says that:
${r"${foo}"}
will print out:
${foo}
But what I need is to print out:
${foo"bar"}
You can't escape the quote in a raw string literal, but you have two kind of quotes to chose from (" and '), so in this case you could write ${r'${foo"bar"}'}. If you are unlucky and you need both kind of quotes inside the raw string literal, then you will have to use a normal string literal with \ escapes, like \{.
(Note that in case you have a lot of ${}-s that FreeMarker shouldn't interpret, then maybe you should set the interpolation_syntax configuration setting to square_bracket, so that ${} is not special for FreeMarker anymore.)
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")
Why does this string not split on each "\n"? (RUBY)
"ADVERTISING [7310]\n\t\tIRS NUMBER:\t\t\t\t061340408\n\t\tSTATE OF INCORPORATION:\t\t\tDE\n\t\tFISCAL YEAR END:\t\t\t0331\n\n\tFILING VALUES:\n\t\tFORM TYPE:\t\t10-Q\n\t\tSEC ACT:\t\t1934 Act\n\t".split('\n')
>> ["ADVERTISING [7310]\n\t\tIRS NUMBER:\t\t\t\t061340408\n\t\tSTATE OF INCORPORATION:\t\t\tDE\n\t\tFISCAL YEAR END:\t\t\t0331\n\n\tFILING VALUES:\n\t\tFORM TYPE:\t\t10-Q\n\t\tSEC ACT:\t\t1934 Act\n\t"]
You need .split("\n"). String interpolation is needed to properly interpret the new line, and double quotes are one way to do that.
In Ruby single quotes around a string means that escape characters are not interpreted. Unlike in C, where single quotes denote a single character. In this case '\n' is actually equivalent to "\\n".
So if you want to split on \n you need to change your code to use double quotes.
.split("\n")
Ruby has the methods String#each_line and String#lines
returns an enum:
http://www.ruby-doc.org/core-1.9.3/String.html#method-i-each_line
returns an array:
http://www.ruby-doc.org/core-2.1.2/String.html#method-i-lines
I didn't test it against your scenario but I bet it will work better than manually choosing the newline chars.
Or a regular expression
.split(/\n/)
You can't use single quotes for this:
"ADVERTISING [7310]\n\t\tIRS NUMBER:\t\t\t\t061340408\n\t\tSTATE OF INCORPORATION:\t\t\tDE\n\t\tFISCAL YEAR END:\t\t\t0331\n\n\tFILING VALUES:\n\t\tFORM TYPE:\t\t10-Q\n\t\tSEC ACT:\t\t1934 Act\n\t".split("\n")
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"
The task is simple - I have a string like "I don't know" and I want substitute ' with \' (I know that I don't have to escape single quotes). How can I do it?
Try using the block form, it should work in all versions of Ruby:
s.gsub(/'/) {"\\'"}
# => "I don\\'t know"
[Edit]
The reason is that the gsub method has special handling for backslash sequences in the replacement string which correspond to the special match variables. So you can use $' (and $1, etc.) directly in the substituted string by using the form \\' (and \\1, etc.) instead.
The block form of gsub doesn't have this behavior, so that's the workaround when you're trying to sub in a string that looks like a special backslash sequence.