A reader for hledger's (and c++ ledger's) journal file format.

From the ledger 2.5 manual:

The ledger file format is quite simple, but also very flexible. It supports
many options, though typically the user can ignore most of them. They are
summarized below.  The initial character of each line determines what the
line means, and how it should be interpreted. Allowable initial characters
are:

NUMBER      A line beginning with a number denotes an entry. It may be followed by any
            number of lines, each beginning with whitespace, to denote the entrys account
            transactions. The format of the first line is:

DATE[=EDATE] [*|!] [(CODE)] DESC

If * appears after the date (with optional eective date), it indicates the entry
            is cleared, which can mean whatever the user wants it t omean. If ! appears
            after the date, it indicates d the entry is pending; i.e., tentatively cleared from
            the users point of view, but not yet actually cleared. If a CODE appears in
            parentheses, it may be used to indicate a check number, or the type of the
            transaction. Following these is the payee, or a description of the transaction.
            The format of each following transaction is:

ACCOUNT     AMOUNT    [; NOTE]

The ACCOUNT may be surrounded by parentheses if it is a virtual
            transactions, or square brackets if it is a virtual transactions that must
            balance. The AMOUNT can be followed by a per-unit transaction cost,
            by specifying  AMOUNT, or a complete transaction cost with @ AMOUNT.
            Lastly, the NOTE may specify an actual and/or eective date for the
            transaction by using the syntax [ACTUAL_DATE] or [=EFFECTIVE_DATE] or
            [ACTUAL_DATE=EFFECtIVE_DATE].

=           An automated entry. A value expression must appear after the equal sign.
            After this initial line there should be a set of one or more transactions, just as
            if it were normal entry. If the amounts of the transactions have no commodity,
            they will be applied as modifiers to whichever real transaction is matched by
            the value expression.

~           A period entry. A period expression must appear after the tilde.
            After this initial line there should be a set of one or more transactions, just as
            if it were normal entry.

!           A line beginning with an exclamation mark denotes a command directive. It
            must be immediately followed by the command word. The supported commands
            are:

!include
                        Include the stated ledger file.
           !account
                        The account name is given is taken to be the parent of all transac-
                        tions that follow, until !end is seen.
           !end       Ends an account block.

;          A line beginning with a colon indicates a comment, and is ignored.

Y          If a line begins with a capital Y, it denotes the year used for all subsequent
           entries that give a date without a year. The year should appear immediately
           after the Y, for example: Y2004. This is useful at the beginning of a file, to
           specify the year for that file. If all entries specify a year, however, this command
           has no eect.

P          Specifies a historical price for a commodity. These are usually found in a pricing
           history file (see the -Q option). The syntax is:

P DATE SYMBOL PRICE

N SYMBOL   Indicates that pricing information is to be ignored for a given symbol, nor will
           quotes ever be downloaded for that symbol. Useful with a home currency, such
           as the dollar ($). It is recommended that these pricing options be set in the price
           database file, which defaults to ~/.pricedb. The syntax for this command is:

N SYMBOL

D AMOUNT   Specifies the default commodity to use, by specifying an amount in the expected
           format. The entry command will use this commodity as the default when none
           other can be determined. This command may be used multiple times, to set
           the default flags for dierent commodities; whichever is seen last is used as the
           default commodity. For example, to set US dollars as the default commodity,
           while also setting the thousands flag and decimal flag for that commodity, use:

D $1,000.00

C AMOUNT1 = AMOUNT2
           Specifies a commodity conversion, where the first amount is given to be equiv-
           alent to the second amount. The first amount should use the decimal precision
           desired during reporting:

C 1.00 Kb = 1024 bytes

i, o, b, h
           These four relate to timeclock support, which permits ledger to read timelog
           files. See the timeclocks documentation for more info on the syntax of its
           timelog files.