I am working on the scripting program with Prolog, where they talk through the pipe and JSON-formatted data. Everything works fine except the json_read_dict/2 relation.
?- json_read_dict(F, "[{\"offset\":22784,\"esil\":\"ebp,ebp,^=,$z,zf,=,$p,pf,=,$s,sf,=,$0,cf,=,$0,of,=,0xffffffff,rbp,&=\",\"refptr\":false,\"fcn_addr\":0,\"fcn_last\":0,\"size\":2,\"opcode\":\"xor ebp, ebp\",\"disasm\":\"xor ebp, ebp\",\"bytes\":\"31ed\",\"family\":\"cpu\",\"type\":\"xor\",\"type_num\":28,\"type2_num\":0,\"flags\":[\"entry0\",\"rip\"]}]\n\n").
ERROR: Arguments are not sufficiently instantiated
ERROR: In:
ERROR: [11] get_code(_1324,_1326)
ERROR: [10] json:json_value(_1356,_1358,_1360,json_options(null,true,false,string,'')) at /usr/lib64/swipl-7.6.4/library/http/json.pl:260
ERROR: [9] json:json_read_dict(_1404,"[{\"offset\":22784,\"esil\":\"ebp,ebp,^=,$z,zf,=,$p,pf,=,$s,sf,=,$0,cf,=,$0,of,=,0xffffffff,rbp,&=\",\"refptr\":false,\"fcn_addr\":0,\"fcn_last\":0,\"size\":2,\"opcode\":\"xor ebp, ebp\",\"disasm\":\"xor ebp, ebp\",\"bytes\":\"31ed\",\"family\":\"cpu\",\"type\":\"xor\",\"type_num\":28,\"type2_num\":0,\"flags\":[\"entry0\",\"rip\"]}]\n\n",[]) at /usr/lib64/swipl-7.6.4/library/http/json.pl:934
ERROR: [7] <user>
ERROR:
ERROR: Note: some frames are missing due to last-call optimization.
ERROR: Re-run your program in debug mode (:- debug.) to get more detail.
How it is possible to parse this output with SWI-Prolog?
The json_read_dict/2 predicate takes a stream or stream alias as first argument. You cannot call it with the first argument unbound, hence the instantiation error. Maybe you're looking for the functionality of the atom_json_dict/3 predicate?
?- atom_json_dict("[{\"offset\":22784,\"esil\":\"ebp,ebp,^=,$z,zf,=,$p,pf,=,$s,sf,=,$0,cf,=,$0,of,=,0xffffffff,rbp,&=\",\"refptr\":false,\"fcn_addr\":0,\"fcn_last\":0,\"size\":2,\"opcode\":\"xor ebp, ebp\",\"disasm\":\"xor ebp, ebp\",\"bytes\":\"31ed\",\"family\":\"cpu\",\"type\":\"xor\",\"type_num\":28,\"type2_num\":0,\"flags\":[\"entry0\",\"rip\"]}]\n\n", D, []).
D = [_19642{bytes:"31ed", disasm:"xor ebp, ebp", esil:"ebp,ebp,^=,$z,zf,=,$p,pf,=,$s,sf,=,$0,cf,=,$0,of,=,0xffffffff,rbp,&=", family:"cpu", fcn_addr:0, fcn_last:0, flags:["entry0", "rip"], offset:22784, opcode:"xor ebp, ebp", refptr:false, size:2, type:"xor", type2_num:0, type_num:28}].
Update
It seems that you get the json(illegal_json) syntax error due to the presence of a starting quote in the output that we're trying to parse. Try instead:
read_result(Out, Json) :-
read_string(Out, "", "", _, String),
atom_json_dict(String, Json, []).
Using your sample call:
?- with_command("/bin/ls", "ij", O).
O = _5058{bin:_4930{arch:"x86", binsz:38688, bintype:"mach0", bits:64, canary:true, checksums:_4926{}, class:"MACH064", compiled:"", crypto:false, dbg_file:"", endian:"little", guid:"", havecode:true, intrp:"/usr/lib/dyld", lang:"c", linenum:false, lsyms:false, machine:"x86 64 all", maxopsz:16, minopsz:1, nx:false, os:"macos", pcalign:0, pic:true, relocs:false, retguard:false, rpath:"", static:false, stripped:true, subsys:"darwin", va:true}, core:_4498{block:256, fd:3, file:"/bin/ls", format:"mach064", humansz:"37.8K", iorw:false, mode:"r-x", obsz:0, size:38688, type:"Executable file"}}.
Related
I am trying to parse a json payload sent via a POST request to a NGINX/Openresty location. To do so, I combined Openresty's content_by_lua_block with its cjson module like this:
# other locations above
location /test {
content_by_lua_block {
ngx.req.read_body()
local data_string = ngx.req.get_body_data()
local cjson = require "cjson.safe"
local json = cjson.decode(data_string)
local endpoint_name = json['endpoint']['name']
local payload = json['payload']
local source_address = json['source_address']
local submit_date = json['submit_date']
ngx.say('Parsed')
}
}
Parsing sample data containing all required fields works as expected. A correct JSON object could look like this:
{
"payload": "the payload here",
"submit_date": "2018-08-17 16:31:51",
},
"endpoint": {
"name": "name of the endpoint here"
},
"source_address": "source address here",
}
However, a user might POST a differently formatted JSON object to the location. Assume a simple JSON document like
{
"username": "JohnDoe",
"password": "password123"
}
not containing the desired fields/keys.
According to the cjson module docs, using cjson (without its safe mode) will raise an error if invalid data is encountered. To prevent any errors being raised, I decided to use its safe mode by importing cjson.safe. This should return nil for invalid data and provide the error message instead of raising the error:
The cjson module will throw an error during JSON conversion if any invalid data is encountered. [...]
The cjson.safe module behaves identically to the cjson module, except when errors are encountered during JSON conversion. On error, the cjson_safe.encode and cjson_safe.decode functions will return nil followed by the error message.
However, I do not encounter any different error handling behavior in my case and the following traceback is shown in Openresty's error.log file:
2021/04/30 20:33:16 [error] 6176#6176: *176 lua entry thread aborted: runtime error: content_by_lua(samplesite:50):16: attempt to index field 'endpoint' (a nil value)
Which in turn results in an Internal Server Error:
<html>
<head><title>500 Internal Server Error</title></head>
<body>
<center><h1>500 Internal Server Error</h1></center>
<hr><center>openresty</center>
</body>
</html>
I think a workaround might be writing a dedicated function for parsing the JSON data and calling it with pcall() to catch any errors. However, this would make the safe mode kind of useless. What am I missing here?
Your “simple JSON document” is a valid JSON document. The error you are facing is not related to cjson, it's a standard Lua error:
resty -e 'local t = {foo = 1}; print(t["foo"]); print(t["foo"]["bar"])'
1
ERROR: (command line -e):1: attempt to index field 'foo' (a number value)
stack traceback:
...
“Safeness” of cjson.safe is about parsing of malformed documents:
cjson module raises an error:
resty -e 'print(require("cjson").decode("[1, 2, 3"))'
ERROR: (command line -e):1: Expected comma or array end but found T_END at character 9
stack traceback:
...
cjson.safe returns nil and an error message:
resty -e 'print(require("cjson.safe").decode("[1, 2, 3"))'
nilExpected comma or array end but found T_END at character 9
Does anybody understand the following behavior inside a ClojureScript browser repl? (provided by the boot tool chain)
my.core> (require 'cljs.pprint)
nil
my.core> (cljs.pprint/pprint "one")
#object[TypeError TypeError: cljs.pprint is undefined]
No stacktrace available.
my.core> (cljs.pprint/pprint "one" "two" "three")
WARNING: Wrong number of args (3) passed to cljs.pprint/pprint at line 1 <cljs repl>
#object[TypeError TypeError: cljs.pprint is undefined]
No stacktrace available.
It looks, that there is no reference to cljs.pprint/pprint, however the repl knows about the arity of this function.
this might help as well:
my.core> (cljs.repl/dir cljs.pprint)
t_cljs$pprint28171
t_cljs$pprint28177
with-pprint-dispatch
with-pretty-writer
write
write-out
nil
cider-repl-toggle-pretty-printing did the trick.
I am calling a R script from Scala by using scala.sys.process. This script takes a command line argument in JSON format and processes it. I am using rjson's fromJSON function to store the JSON in a list.
This works very fine when I execute the R script from the command line:
$ ./dfChargerFlink.R '{"Id":"1","value":"ABC"}'
But when I call it from scala, I get the following error:
Error in fromJSON(commandArgs(1)) : unexpected character '''
Execution halted
This is the code I am using:
val shellCommand = "./dfChargerFlink.R '"+arg+"'"
return shellCommand !!
where arg is the JSON string.
You can notice that I have appended " ' " to both the sides of the JSON string as if I don't, I get this error:
Error in fromJSON(commandArgs(1)) : unclosed string
Execution halted
How can this be solved? Is it some bug?
I have the following SML program in a file named testexc.sml:
structure TestExc : sig
val main : (string * string list -> int)
end =
struct
exception OhNoes;
fun main(prog_name, args) = (
raise OhNoes
)
end
I build it with smlnj-110.74 like this:
ml-build sources.cm TestExc.main testimg
Where sources.cm contains:
Group is
csx.sml
I invoke the program like so (on Mac OS 10.8):
sml #SMLload testimg.x86-darwin
I expect to see something when I invoke the program, but the only thing I get is a return code of 1:
$ sml #SMLload testimg.x86-darwin
$ echo $?
1
What gives? Why would SML fail silently on this unhandled exception? Is this behavior normal? Is there some generic handler I can put on main that will print the error that occurred? I realize I can match exception OhNoes, but what about larger programs with exceptions I might not know about?
The answer is to handle the exception, call it e, and print the data using a couple functions available in the system:
$ sml
Standard ML of New Jersey v110.74 [built: Tue Jan 31 16:23:10 2012]
- exnName;
val it = fn : exn -> string
- exnMessage;
val it = fn : exn -> string
-
Now, we have our modified program, were we have the generic handler tacked on to main():
structure TestExc : sig
val main : (string * string list -> int)
end =
struct
exception OhNoes;
open List;
fun exnToString(e) =
List.foldr (op ^) "" ["[",
exnName e,
" ",
exnMessage e,
"]"]
fun main(prog_name, args) = (
raise OhNoes
)
handle e => (
print("Grasshopper disassemble: " ^ exnToString(e));
42)
end
I used lists for generating the message, so to make this program build, you'll need a reference to the basis library in sources.cm:
Group is
$/basis.cm
sources.cm
And here's what it looks like when we run it:
$ sml #SMLload testimg.x86-darwin
Grasshopper disassemble: [OhNoes OhNoes (more info unavailable: ExnInfoHook not initialized)]
$ echo $?
42
I don't know what ExnInfoHook is, but I see OhNoes, at least. It's too bad the SML compiler didn't add a basic handler for us, so as to print something when there was an unhandled exception in the compiled program. I suspect ml-build would be responsible for that task.
I am using the R package rjson to download weather data from Wunderground.com. Often I leave the program to run and there are no problems, with the data being collected fine. However, often the program stops running and I get the following error message:
Error in fromJSON(paste(raw.data, collapse = "")) : unclosed string
In addition: Warning message:
In readLines(conn, n = -1L, ok = TRUE) :
incomplete final line found on 'http://api.wunderground.com/api/[my_API_code]/history_20121214pws:1/q/pws:IBIRMING7.json'
Does anyone know what this means, and how I can avoid it since it stops my program from collecting data as I would like?
Many thanks,
Ben
I can recreate your error message using the rjson package.
Here's an example that works.
rjson::fromJSON('{"x":"a string"}')
# $x
# [1] "a string"
If we omit a double quote from the value of x, then we get the error message.
rjson::fromJSON('{"x":"a string}')
# Error in rjson::fromJSON("{\"x\":\"a string}") : unclosed string
The RJSONIO package behaves slightly differently. Rather than throwing an error, it silently returns a NULL value.
RJSONIO::fromJSON('{"x":"a string}')
# $x
# NULL