Boost C++ Libraries of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for an old version of Boost. Click here to view this page for the latest version.

read_until (2 of 8 overloads)

Read data into a streambuf until it contains a specified delimiter.

    typename SyncReadStream,
    typename Allocator>
std::size_t read_until(
    SyncReadStream & s,
    boost::asio::basic_streambuf< Allocator > & b,
    char delim,
    boost::system::error_code & ec);

This function is used to read data into the specified streambuf until the streambuf's get area contains the specified delimiter. The call will block until one of the following conditions is true:

This operation is implemented in terms of zero or more calls to the stream's read_some function. If the streambuf's get area already contains the delimiter, the function returns immediately.



The stream from which the data is to be read. The type must support the SyncReadStream concept.


A streambuf object into which the data will be read.


The delimiter character.


Set to indicate what error occurred, if any.

Return Value

The number of bytes in the streambuf's get area up to and including the delimiter. Returns 0 if an error occurred.


After a successful read_until operation, the streambuf may contain additional data beyond the delimiter. An application will typically leave that data in the streambuf for a subsequent read_until operation to examine.