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Asked: 2026-06-06T04:08:55+00:00

I tried to split two fields from a binary string: -define(S,<<M\0\0\0522039355099,010100000008,0,010170000000,0,0,0,0,0,0,,,0,0,,‌​0110,00,150,0,0,0\0>>).<<Message_length:4/binary,Msg/binary>> = S. the

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I tried to split two fields from a binary string: 

-define(S,<<"M\0\0\0522039355099,010100000008,0,010170000000,0,0,0,0,0,0,,,0,0,,‌​0110,00,150,0,0,0\0">>).<<Message_length:4/binary,Msg/binary>> = S.

the first 4 bytes are the length of the following message, the other byte are the message,
a null byte terminates the string.

The result is:
** exception error: o match of right hand side value
EDIT
Just before the given code, there is: 

[Sequence|Reste] = binary:split(T,<<"\0">>),

Does “Reste” bounded ?

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1 Answer

  1. Editorial Team

    Your code is ok, so either you dont have a binary string, or the length of Mystring does not comply with the pattern. Here’s a quick test:

    1> Mystring = <<"abcde">>.
<<"abcde">>
2> <<Message_length:4/binary,Msg/binary>> = Mystring.
<<"abcde">>
3> Message_length.
<<"abcd">>
4> Msg.
<<"e">>

    If you have a string (a list of integers) instead of a binary string (<<“string”>>), as Vincenzo suggested, call erlang:list_to_binary/1 first.

    Hope it helps

    EDIT: I’ve checked the example string you left in a comment of Vincenzo’s answer. I’ve tried it with your code and still works. Is it possible that Message_length and/or Msg are already bound (and different to Mystring) when reaching that line of code? That would make the pattern matching fail.

    EDIT2: Tested with the updated data in the question:

    1> S = <<"M\0\0\0522039355099,010100000008,0,010170000000,0,0,0,0,0,0,,,0,0,,\342\200\214\342\200\2130110,00,150,0,0,0\0">>.
<<77,0,0,42,50,48,51,57,51,53,53,48,57,57,44,48,49,48,49,
  48,48,48,48,48,48,48,56,44,48,...>>
2> <<Message_length:4/binary,Msg/binary>> = S.
<<77,0,0,42,50,48,51,57,51,53,53,48,57,57,44,48,49,48,49,
  48,48,48,48,48,48,48,56,44,48,...>>
3> Message_length.
<<77,0,0,42>>
4> Msg.
<<"2039355099,010100000008,0,010170000000,0,0,0,0,0,0,,,0,0,,\342"...>>
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