file_read_helpers

file_read_helpers
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Name

file_read_line, file_rl, file_rb, file_rlo, file_rlc, read_object, get_plaintext_row — read lines, bytes and serialized objects from files and sessions

Synopsis

`varchar file_read_line(`	in `file` varchar,
	in `offset` integer`)`;

`any file_rl(`	inout `handle` any,
	in `line_offset` integer,
	in max_len integer`)`;

`any file_rb(`	inout `handle` any,
	in `length` integer`)`;

any file_rlo( in file varchar);

integer file_rlc( inout handle any);

any read_object( inout session any);

varchar get_plaintext_row( inout session any);

Description

file_read_line reads a single line from file starting at byte offset, advancing the returned text up to the next newline (which is consumed). Convenient for scanning configuration or log files when only an offset-based seek is needed. Requires DBA privileges.

file_rl, file_rb, file_rlo and file_rlc implement a stateful file-line / file-buffer reading API:

:  file_rlo	open a file for line-oriented reading; returns a handle to be passed to
:	file_rl / file_rb / file_rlc.
:  file_rl	read one line starting at <line_offset>, optionally bounded by <max_len>
:	bytes (default 80 KiB).
:  file_rb	read exactly <length> raw bytes from the open handle.
:  file_rlc	close the open handle and free its resources. Returns 1 on success.

All four require DBA privileges. The handle returned by file_rlo is an opaque file-descriptor box and must be passed to file_rlc when reading is complete.

read_object deserialises one Virtuoso-format object (anything that can be produced by serialize) from session and returns it. Use it to read structured payloads written by Virtuoso-internal RPC or file-format consumers.

get_plaintext_row reads a single tab-separated text row from session and returns it as a string, with the trailing newline stripped. Pairs naturally with bulk-load procedures and CSV scanning.

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