I am trying to add %20 between the date and time, to return YYY-MM-DD%20HH-MM-SS
How can I escape the % symbol?
date '+%Y-%m-%d%20%H:%M:%S'
Returns:
2023-02-06 %H:12:40
And when I quote the %20:
date '+%Y-%m-%d\"%20\"%H:%M:%S'
The quotes are also returned:
2023-02-06"%20"11:13:59
The conversion specifier %% expands to a literal %
$ date +%%
%
so
$ date '+%Y-%m-%d%%20%H:%M:%S'
2023-02-06%2011:20:17
However, as this implies you are using the string in a URL, I would recommend simply outputting a space, and letting whatever is constructing the URL ensure that necessary characters are escaped.
You can escape the % with another %, i.e. by doubling it:
$ date '+%Y-%m-%d%%20%H:%M:%S'
2023-02-06%2017:19:38
As noted in date(1):
FORMAT controls the output. Interpreted sequences are:
%% a literal %
Related
I have a string like : 2021_03_19/ 19-Mar-2021 11:55 -
stored in a variable a
I tried to extract from it the sequence: 2021_03_19, the second one after /"> sequence with the following script:
a=${a##'/">'}
a=${a%%'/</a'}
But the final result is the same string as the input.
The pattern in the parameter expansion needs to match the entire string you want to remove. You are trying to trim the literal prefix /"> but of course the string does not begin with this string, so the parameter expansion does nothing.
Try
a=${a##*'/">'}
a=${a%%'/</a'*}
The single quotes are kind of unusual; I would perhaps instead backslash-escape each metacharacter which should be matched literally.
a=${a##*/\"\>}
a=${a%%/\</a*}
You have to match the before and after pattern too.
a=${a##*'/">'}
a=${a%%'/</a'*}
You could use:
a='2021_03_19/ 19-Mar-2021 11:55 -'
b=${a#*>}
c=${b%%/<*}
Based on Extract substring in Bash
In your example you want to select based on 3 characters but have ##, not ###. I did try that but doesn't seem to work either. So, therefore an alternative solution.
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'm writing a Ruby command line application in which the user has to enter a "format string" (much like Date.strptime/strftime's strings).
I tried taking them in as arguments to the command, eg
> torque "%A\n%d\n%i, %u"
but it seems that bash actually removes all backslashes from input before it can be processed (plus a lot of trouble with spaces). I also tried the highline gem, which has some more advanced input options, but that automatically escapes backslashes "\" -> "\\" and provides no alternate options.
My current solution is to do a find-and-replace: "\\n" -> "\n". This would take care of the problem, but it also seems hacky and awful.
I could have users write the string in a text file (complicated for the user) or treat some other character, like "&&", as a newline (still complicated for the user).
What is the best way for users to input escaped characters on the command line?
(UPDATE: I checked the documentation for strptime/strftime, and the format strings for those functions replace newline characters with "%n", tabs with "%t", etc. So for now I'm doing that, but any other suggestions are welcome)
What you're looking for is using single quotes instead of double quotes.
Thus:
> torque '%A\n%d\n%i, %u'
Any string quoted in single quotes 'eg.' is does not go through any expansions and is used as is.
More details can be found in the Quoting section of man bash.
From man bash:
Enclosing characters in single quotes preserves the literal value of each character within the quotes. A single quote may not occur between single quotes, even when preceded by a backslash.
p eval("\"#{gets.chomp}\"")
Example use:
\n\b # Input by the user from the keyboard
"\n\b" # Value from the script
%A\n%d\n%i, %u # Input by the user from the keyboard
"%A\n%d\n%i, %u" # Value from the script
I've recently discovered that Awk's -v VAR=VAL syntax for initializing variables on the command line expands escape sequences in VAL. I previously thought that it was a good way to pass strings into Awk without needing to run an escaping function over them first.
For example, the following script:
awk -v VAR='x\tx' 'BEGIN{printf("%s\n", VAR);}'
I would expect to print
x\tx
but actually prints:
x x
An aside: environment variables to pass strings in unmodified instead, this question isn't asking how to get the behaviour I previously expected.
Here's what the man page has to say on the matter:
-v var=val, --assign var=val Assign the value val to the variable var, before execution of the program begins. Such variable values are available to the
BEGIN block of an AWK program.
And further down:
String Constants
String constants in AWK are sequences of characters enclosed between double quotes (like "value"). Within strings, certain escape
sequences are recognized, as in C. These are:
... list of escape seqeuences ...
The escape sequences may also be used inside constant regular expressions (e.g., /[ \t\f\n\r\v]/ matches whitespace characters).
In compatibility mode, the characters represented by octal and hexadecimal escape sequences are treated literally when used in
regular expression constants. Thus, /a\52b/ is equivalent to /a*b/.
The way I read this, val in -v var=val is not a string constant, and there is no text to indicate that the string constant escaping rules apply.
My questions:
Is there a more authoritative source for the awk language than the man page, and if so what does it specify?
What does POSIX have to say about this, if anything?
Do all versions of Awk behave this way, i.e. can I rely on the expansion being done if I actually want it?
The assignment is a string constant.
The relevant sections from the standard are:
-v assignment
The application shall ensure that the assignment argument is in the same form as an assignment operand. The specified variable assignment shall occur prior to executing the awk program, including the actions associated with BEGIN patterns (if any). Multiple occurrences of this option can be specified.
and
An operand that begins with an underscore or alphabetic character from the portable character set (see the table in XBD Portable Character Set ), followed by a sequence of underscores, digits, and alphabetics from the portable character set, followed by the '=' character, shall specify a variable assignment rather than a pathname. The characters before the '=' represent the name of an awk variable; if that name is an awk reserved word (see Grammar ) the behavior is undefined. The characters following the <equals-sign> shall be interpreted as if they appeared in the awk program preceded and followed by a double-quote ( ' )' character, as a STRING token (see Grammar ), except that if the last character is an unescaped , it shall be interpreted as a literal rather than as the first character of the sequence "\""
I am currently using Watir with Firefox and it seems that when I try to set a field with the following text:
##$QWER7890uiop
The command I am using is the following:
text_field(:name, "password").value=("!##$QWER7890uiop)
I've also tried this:
text_field(:name, "password").set "!##$QWER7890uiop)
Only the first 2 characters get entered. Is there something I can do to by pass this feature?
You need to escape the string using single quotes '.
text_field(:name, "password").value='"!##$QWER7890uiop'
Many characters are substituted inside double quotes.
Escape sequences like \n, \t, \s, etc are replaced by their equivalent character(s). See here for full list.
#{} where anything the braces is interpreted as a ruby expression.
#$something where $something is interpreted as a ruby global variable. That's the problem with your quote above, beside not being terminated.
%s is interpreted as an ERB template expression (it is interpolated).
For instance:
puts "%s hours later" % 'Five'
results in
"Five hours later".