lags is a bitwise or of the constants below. These flags map to options for write_term/2.

PL_WRT_QUOTED

PL_WRT_IGNOREOPS

PL_WRT_NUMBERVARS

PL_WRT_PORTRAY

PL_WRT_CHARESCAPES

PL_WRT_NO_CHARESCAPES

The PL_WRT_NO_CHARESCAPES does not map to a write_term/2 option. If one of PL_WRT_CHARESCAPES or PL_WRT_NO_CHARESCAPES is specified, character escapes are (not) applied. If neither is specified the default depends, like for write/1, on the character_escapes flag on the module user.^{231Prior to version 9.1.6 the default (no flag) was to escape the quotes and the backslash (\).}

PL_WRT_BACKQUOTED_STRING

PL_WRT_ATTVAR_IGNORE

PL_WRT_ATTVAR_DOTS

PL_WRT_ATTVAR_WRITE

PL_WRT_ATTVAR_PORTRAY

PL_WRT_BLOB_PORTRAY

PL_WRT_NO_CYCLES

PL_WRT_NEWLINE

PL_WRT_VARNAMES

PL_WRT_BACKQUOTE_IS_SYMBOL

PL_WRT_DOTLISTS

PL_WRT_BRACETERMS

PL_WRT_NODICT

PL_WRT_NODOTINATOM

PL_WRT_NO_LISTS

PL_WRT_RAT_NATURAL

PL_WRT_CHARESCAPES_UNICODE

PL_WRT_QUOTE_NON_ASCII

PL_WRT_PARTIAL

For example, to print a term to user_error as the toplevel does, use

    PL_write_term(Suser_error, t, 1200,
                  PL_WRT_QUOTED|PL_WRT_PORTRAY|
                  PL_WRT_VARNAMES|PL_WRT_NEWLINE)

12.9.4 Foreign stream error handling

int Sferror(IOSTREAM *s)

Returns TRUE if the stream is in an error condition, FALSE if the stream is valid and in normal condition and -1 if the stream is invalid.

void Sclearerr(IOSTREAM *s)

Clear the error state of a stream. This includes the end-of-file state, pending warnings and errors and timeout.

int Sseterr(IOSTREAM *s, int which, const char *message)

Set an error or warning state on the stream. The which argument is one of SIO_WARN or SIO_FERR. This