Query from ejabberd module with LIKE %% - erlang

I have this lines of code in ejabberd module, it works fine:
case catch ejabberd_odbc:sql_query(Server,["select COUNT(*) as total from spool where username='",IdUsername,"' AND xml LIKE '%message from%' AND xml LIKE '%chat%';"]) of
{selected, [<<"total">>], [[Totale]]} ->
Count = binary_to_list(Totale);
_ -> Count = "0"
end,
If I convert this:
LIKE '%chat%';
with this:
LIKE '%type=\'chat\'%';
I obtain an error, any ideas? or there's another way to get only the chat message?


Since you're typing this in an Erlang string, the Erlang escape sequences apply. In particular, \' is an escape sequence for just a single quote, '. (That's more useful inside atoms, which are delimited by single quotes.)
You can try it in an Erlang shell, and see that "\'" and "'" are equivalent:
1> "\'".
"'"
2> "\'" =:= "'".
true
To include an actual backslash in the string, escape it with another backslash:
"\\'"
In your case, that would be:
LIKE '%type=\\'chat\\'%';

Related

How to replace double quotes in Erlang

This is probably a rather trivial question for the Erlang experts - I'm trying to have my ejabberd server store offline messages (in a Riak db) which inherently do contain double quotes (") around various values, etc. I get a format error when I try to create a Riak database object from them, and testing of replacing the double quotes with an escape character (\") corrects the issue. The question is how can I do this replacement manually?
I tried the following code but somehow doesn't work.
(ejabberd#xxx-xx-xx-xxx)4> re:replace(""hello"", """, "\"", [{return, list}, global]).
* 1: syntax error before: hello
So essentially I'm trying to replace the embedded " around the hello word with \".

I don't know Erlang, but you probably need something like this:
"\"hello\"", "\"", "\\\""

You must escape both " and \ in replacement string.
The Erlang literal syntax for strings uses the "\" (backslash)
character as an escape code. You need to escape backslashes in literal
strings, both in your code and in the shell, with an additional
backslash, i.e.: "\".
Example:
Let's make an example. I use $ Erlang symbol which will be substituted with ascii integer of a character to show what is happening behind each string which basically is a list of integer.
Subject = [$"] ++ "hello" ++ [$"] = "\"hello\"".
Target = [$"] = "\"".
Replacement = [$\\, $\\, $"] = "\\\\\"".
Result = re:replace(Subject, Target, Replacement, [{return, list}, global]).
Now with getting the length of Subject and Result we can find the difference:
7 = length(Subject). %% => 7 characters: " h e l l o "
9 = length(Result). %% => 9 characters: \ " h e l l o \ "

Converting a tuple to a string in erlang language

Tuple={<<"jid">>,Member},
Tuple_in_string=lists:flatten(io_lib:format("~p", [Tuple])),
it gives output as:
"{<<\"jid\">>,\"sdfs\"}"
But i want this output without these slashes like
"{<<"jid">>,Member}"
Any pointers?
I have tried all the answers but at the end with io:format("\"~s\"~n", [Tuple_in_string]). what am geeting is "{<<"jid">>,Member}" but it is not a string.it is a atom.I need string on which i can apply concat operation.Any pointers?

You can print it like this:
io:format("\"~s\"~n", [Tuple_in_string]).
It prints:
"{<<"jid">>,"sdfs"}"

The \ are here to denote that the following " is part of the string and not a string delimiter. they do not exist in the string itself. They appear because you use the pretty print format ~p. If you use the string format ~s they wont appear in the display.
1> io:format("~p~n",["a \"string\""]).
"a \"string\""
ok
2> io:format("~s~n",["a \"string\""]).
a "string"
ok
3> length("a \"string\""). % is 10 and not 12
10

Firstly, you don't need to flatten the list here:
Tuple_in_string=lists:flatten(io_lib:format("~p", [Tuple])),
Erlang has the concept of iodata(), which means that printable things can be in nested lists and most functions can handle them, so you should leave only:
Tuple_in_string = io_lib:format("~p", [Tuple]),
Secondly, when you use ~p, you tell Erlang to print the term in such way, that it can be copied and pasted into console. That is why all double quotes are escaped \". Use ~s, which means "treat as string".
1> 38> Tuple = {<<"jid">>,"asdf"}.
{<<"jid">>,"asdf"}
2> IODATA = io_lib:format("~p", [Tuple]).
[[123,[[60,60,"\"jid\"",62,62],44,"\"asdf\""],125]]
3> io:format("~s~n", [IODATA]).
{<<"jid">>,"asdf"}
ok

L = Packet_in_tuple_form={xmlel,<<"message">>,[{<<"id">>,<<"rkX6Q-8">>},{<<"to">>,<<"multicast.devlab">>}],[{xmlel,<<"body">>,[],[{xmlcdata,"Hello"}]},{xmlel,<<"addresses">>,[{<<"xmlns">>,<<"http://jabber.org/protocol/address">>}],[{xmlel,<<"address">>,[{<<"type">>,<<"to">>},"{<<\"jid\">>,\"sds\"}",{<<"desc">>,"Description"}],[]}]}]}.
Gives me:
{xmlel,<<"message">>,
[{<<"id">>,<<"rkX6Q-8">>},{<<"to">>,<<"multicast.devlab">>}],
[{xmlel,<<"body">>,[],[{xmlcdata,"Hello"}]},
{xmlel,<<"addresses">>,
[{<<"xmlns">>,<<"http://jabber.org/protocol/address">>}],
[{xmlel,<<"address">>,
[{<<"type">>,<<"to">>},
"{<<\"jid\">>,\"sds\"}",
{<<"desc">>,"Description"}],
[]}]}]}
The \ in the address field are escape characters.
You can verify the same by checking the length of string.

Lua string find - How to handle strings with a hyphen?

I have two strings - each string has many lines like the following:
string1 = " DEFAULT-VLAN | Manual 10.1.1.3 255.255.255.0 "
string2 = " 1 DEFAULT-VLAN | Port-based No No"
The first string I split into the following strings: "DEFAULT-VLAN", "|", "Manual"...
Then I want to look up the ID ("1") in string2 for the vlanName ("DEFAULT-VLAN") from string1.
I use this code to find the correct substring:
vpos1, vpos2 = vlan:find("%d-%s-" .. vlanName .. "%s-|")
But vpos1 and vpos2 are nil; When the hyphen ("-") is deleted from the vlanName it is working.
Shouldn't Lua take care to escape the special characters in such strings? The string is handed over from my C++ application to Lua and there may be lots of special characters.
Is there an easy way to solve this?
Thanks!

Lua is not magic. All the expression "%d-%s-" .. vlanName .. "%s-|" does is concatenate some strings, producing a final string. It has no idea what that string is intended to be used for. Only string.find knows that, and it can't have any affect on how the parameter it is given will be used.
So yes, vlanName will be interpreted as a Lua pattern. And if you want to use special characters, you will need to escape them. I would suggest using string.gsub for that. It'd be something like this:
vlanName:gsub("[%-...]", "%%%0")
Where ... are any other characters you want to escape.

Erlang - io:format 's result / (formatting with io_lib:format/2)

I'm trying to get the result of the output of io:format/1.
I know that there's a similar function in io_lib, io_lib:format/2, but the output is different. In fact, it doesn't do anything at all.
If I try to bound io:format, ok is bounded, and the formatted string is written out to the console.
So my question is, how can I get the same output with io_lib:format/2?
Or how can I bound the formatted string to a variable?
1> A = io:get_line('> ').
> "test".
"\"test\".\n"
2> io:format(A).
"test".
ok
3> B = io_lib:format(A, []).
"\"test\".\n"
4> B.
"\"test\".\n"
5> C = io:format(A).
"test".
ok
6> C.
ok

io_lib:format is not an output function the way io:format is. Instead io_lib:format only returns the value, but does not output it.
The result of io:format that you see as "test." is the rendered version as sent to the terminal (including the newline) , then it returns ok. Conversely, the return value of io_lib:format that you see as "\"test\".\n" is simply the erlang shell's representation of the same string, with the quotes and newline escaped, and surrounded by its own quotes.
io_lib:format is more commonly used for inserting values into the strings (similar to C's printf functions). For example, doing something like
NewString = io_lib:format("The string entered was ~s I hope you like it",[A])
The value of NewString would be
The string entered was "test".
I hope you like it
For which the Erlang Shell's representation would be:
"The string entered was \"test\".\n I hope you like it"
If all you want to do is output the value you just entered, then io:format is sufficient for your needs.

flex usage of (?r-s:pattern)

I am trying to use the regular expression (?r-s:pattern) as mentioned in the Flex manual.
Following code works only when i input small letter 'a' and not the caps 'A'
%%
[(?i:a)] { printf("color"); }
\n { printf("NEWLINE\n"); return EOL;}
. { printf("Mystery character %s\n", yytext); }
%%
OUTPUT
a
colorNEWLINE
A
Mystery character A
NEWLINE
Reverse is also true i.e. if i change the line (?i:a) to (?i:A) it only considers 'A' as valid input and not 'a'.
If I remove the square brackets i.e. [] it gives error as
"ex1.lex", line 2: unrecognized rule
If I enclose the "(?i:a)" then it compiles but after executing it always goes to last rule i.e. "Mystery character..."
Please let me know how to use it properly.

I guess I am late.. :) Anyway, which flex version are you using, I have version 2.5.35 installed and correctly recognizes above pattern. Perhaps you're using old version!!!
Now regarding the enclosing with [] brackets. It works because as per [] regex rule it will try to match any of individual (, ?, i, :, a or ). Thats why a gets recognized and not A (because it is not in the list).

The way I read the manual, the rule without the square brackets should perform the case-insensitive matching you're looking for--I can't explain why you get an error at compile time. But you can achieve the same behavior in one of two ways. One, you can enumerate the upper and lower case characters in the character class:
%%
[Aa] { printf("color"); }
%%
Two, you can specify the case-insensitive scanner option, either on the command line as -i or --case-insensitive or in your .l file:
%%
%option case-insensitive
[a] {printf("color"); }
%%

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