Module Core_extended.Linebuf

Line-by-line reading of a file. A line buffer allows one to read one line of a file at a time, blocking until a line is available. Line buffers are distinct from Pervasives.read_line in that they "notice" new data arriving in the file more quickly.

type t

The type of a line buffer.

type error_type =
| Null_retry
| Too_many_nulls
| Exception of string * exn
type lnum =
| Known of int
| Unknown
type result =
| Success of lnum * string
| Nothing_available
| Error of error_type
| Fatal_error of string * exn
exception File_truncated_or_deleted
val create : ?⁠pos:Int64.t ‑> ?⁠close_on_eof:bool ‑> ?⁠null_hack:[ `Off | `Retry_then_fail | `Retry ] ‑> ?⁠eprint_nulls:bool ‑> ?⁠follow_deletes:bool ‑> ?⁠signal_on_truncate_or_delete:bool ‑> string ‑> t

Open a line buffer from the passed filename. If close_on_eof is set, when eof is read, the file will be closed and reopened if necessary. if follow_deletes is set, then when eof is read linebuf will stat the file, and if it has been deleted and recreated it will open the new file. If eprint_nulls is set, then when nulls are found, a warning message will be printed to stderr. null_hack specifies the behaviour of the linebuf upon reception of null characters in the file (as seen when tailing files over CIFS). Null hack options: `Off: don't check for nulls, just keep going. `Retry: close and reopen file when nulls are read from the file. If max_null_retries is reached, then pass the line with nulls. `Retry_then_fail: the same as retry, except that an exception is raised once max_null_retries is reached.

val close : t ‑> unit

Closes the line buffer (and the underlying file).

val is_closed : t ‑> bool

Returns whether or not the line buffer is closed

val try_read : t ‑> string option

Tries to read a line from the file. If no more lines are available, returns None.

val try_read_lnum : t ‑> (lnum * string) option

try_read_lnum is like try_read except also provides the line number of the read line.

val try_read_lnum_verbose : t ‑> result

Like try_read, except that it returns more verbose errors

val read : t ‑> string

Calls try_read every 0.01 seconds and returns when a line is available.

val tail : t ‑> unit

Seeks to the end of the file and blocks until another line is available -- this new line is not returned. Successive return values of try_read_lnum and try_read_lnum will return Unknown as the current line number until reset is called

val unsafe_tail : t ‑> unit

Same as tail except it may return before a new line is available on the file i.e. it (usually) doesn't block. Note that this does interact with files in a fairly naive way, so there's no guarantee that it absolutely doesn't block.

Note that when this functions is called, the next line that's read may be a partial line. After that first line, only full lines will be read.

val name : t ‑> string
val reset : t ‑> unit

reopens the file and seeks to the beginning. Also recovers the ability to get line numbers if tail has been called