I publish to a lot of channels with binary names. The names look like [binary_data]:[text data]. Sometimes I would like to subscribe to the channel as follows:
PSUBSCRIBE [binary data]:*
In this case if binary data contains an asterisk the matching can deliver unexpected results. Is there a way to escape the asterisk character in this circumstances?
Use \ with the asterisk (or question mark, or any other special char) you want to escape.
From the psubscribe docs:
Use \ to escape special characters if you want to match them verbatim.
Related
I cant think of an OS (Linux, Windows, Unix) where this would cause an issue but maybe someone here can tell me if this approach is undesirable.
I would like to use a base64 encoded string as a filename. Something like gH9JZDP3+UEXeZz3+ng7Lw==. Is this likely to cause issues anywhere?
Edit: I will likely keep this to a max of 24 characters
Edit: It looks like I have a character that will cause issues. My function that generated my string is providing stings like: J2db3/pULejEdNiB+wZRow==
You will notice that this has a / which is going to cause issues.
According to this site the / is a valid base64 character so I will not be able to use a base64 encoded string for a filename.
No. You can not use a base64 encoded string for a filename. This is because the / character is valid for base64 strings which will cause issues with file systems.
https://base64.guru/learn/base64-characters
Alternatives:
You could use base64 and then replace unwanted characters but a better option would be to hex encode your original string using a function like bin2hex().
The official RFC 4648 states:
An alternative alphabet has been suggested that would use "~" as the 63rd character. Since the "~" character has special meaning in some file system environments, the encoding described in this section is recommended instead. The remaining unreserved URI character is ".", but some file system environments do not permit multiple "." in a filename, thus making the "." character unattractive as well.
I also found on the serverfault stackexchange I found this:
There is no such thing as a "Unix" filesystem. Nor a "Windows" filesystem come to that. Do you mean NTFS, FAT16, FAT32, ext2, ext3, ext4, etc. Each have their own limitations on valid characters in names.
Also, your question title and question refer to two totally different concepts? Do you want to know about the subset of legal characters, or do you want to know what wildcard characters can be used in both systems?
http://en.wikipedia.org/wiki/Ext3 states "all bytes except NULL and '/'" are allowed in filenames.
http://msdn.microsoft.com/en-us/library/aa365247(VS.85).aspx describes the generic case for valid filenames "regardless of the filesystem". In particular, the following characters are reserved < > : " / \ | ? *
Windows also places restrictions on not using device names for files: CON, PRN, AUX, NUL, COM1, COM2, COM3, etc.
Most commands in Windows and Unix based operating systems accept * as a wildcard. Windows accepts % as a single char wildcards, whereas shells for Unix systems use ? as single char wildcard.
And this other one:
Base64 only contains A–Z, a–z, 0–9, +, / and =. So the list of characters not to be used is: all possible characters minus the ones mentioned above.
For special purposes . and _ are possible, too.
Which means that instead of the standard / base64 character, you should use _ or .; both on UNIX and Windows.
Many programming languages allow you to replace all / with _ or ., as it's only a single character and can be accomplished with a simple loop.
In Windows, you should be fine as long if you conform to the naming conventions of Windows:
https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file#naming-conventions.
As far a I know, any base64 encoded string does not contain any of the reserves characters.
The thing that is probably going to be a problem is the lengte of the file name.
I'm running a SQL query in PowerShell using the SQLCMD, one of the posts shows how to use TAB as a separator. I'd like to have a fancier sequence of characters such as TAB-Comma-Space or Tab-Comma-Tab.
I've tried
-s `"`t,`t`"
-s `"`t`, `"
but it still uses a single Tab as the separator.
Thanks in advance.
Not possible according to the documentation.
-s col_separator
Specifies the column-separator character. The default is a blank space. This option sets the sqlcmd scripting variable SQLCMDCOLSEP. To use characters that have special meaning to the operating system such as the ampersand (&), or semicolon (;), enclose the character in quotation marks ("). The column separator can be any 8-bit character.
You might want to think about using a character like the hat/caret (^) as your delimiter and mass replacing that in the output. Not sure what single character would be least likely to conflict with your dataset.
I am using sed to replace a placeholder in a script with my public ssh key. The character / is definitely present in some SSH keys, how can I find out which character I can use as delimiter for sed?
I am looking for an answer of either the set of all characters that can be part of the string generated by ssh-keygen, or which characters are guaranteed not to.
The public key in opnessh format is base64-encoded as mentioned for example in the manual page for sshd. Therefore you can use any character that is not in the list of base64 characters. The / is there but for example | can be used safely (though in the comment section can be anything).
For information, from the info sed, section 3.5:
The '/' characters may be uniformly replaced by any other single character within any given 's' command.
The '/' character (or whatever other character is used in its stead) can
appear in the REGEXP or REPLACEMENT only if it is preceded by a '\'
character.
So you can chose any suitable character that doesn't appear in your input data.
I am aware of the naming conventions for Redis keys (this is a great link here Naming Convention and Valid Characters for a Redis Key ) but what of the values? Will I have an issue if my values include characters such as &^*$#+{ ?
From http://redis.io/topics/data-types:
Redis Strings are binary safe, this means that a Redis string can contain any kind of data, for instance a JPEG image or a serialized Ruby object.
A String value can be at max 512 Megabytes in length.
So those chars you've specified will be fine, as will any other data.
#Ruan is not exactly covering the whole story. I have looked close at that section of the Redis docs and it doesn't cover special characters.
For example, you will need to escape double quotes " with a preceding backslash \" in your key.
Also if you do have special characters in your key i.e, spaces, single or double quotes, you will need to wrap your whole key in double quotes.
The following keys are valid and you can use them to start understanding how special characters are handled.
The following allows spaces in your key.
set "users:100:John Doe" 1234
The following allows special characters by escaping them.
set "metadata:2:moniker\"#\"" 1234
When I search one ldap server using the following filter
(cn=%*)
It return all results under the base dn? LDAP treat '%' specially? But I haven't found any description about it.
What is your directory server ?
Are you sure tha '%' is not replace by your command line interpreter or your compiler ?
According to RFC2254 % is not a special character
If a value should contain any of the following characters
Character ASCII value
---------------------------
* 0x2a
( 0x28
) 0x29
\ 0x5c
NUL 0x00
the character must be encoded as the backslash '\' character (ASCII
0x5c) followed by the two hexadecimal digits representing the ASCII
value of the encoded character. The case of the two hexadecimal
digits is not significant.
This simple escaping mechanism eliminates filter-parsing ambiguities
and allows any filter that can be represented in LDAP to be
represented as a NUL-terminated string. Other characters besides the
ones listed above may be escaped using this mechanism, for example,
non-printing characters.
For example, the filter checking whether the "cn" attribute contained
a value with the character "" anywhere in it would be represented as
"(cn=\2a*)".
Note that although both the substring and present productions in the
grammar above can produce the "attr=*" construct, this construct is
used only to denote a presence filter.