First draft of new "--sync" option.

src/include/options.h

@@ -43,6 +43,7 @@ struct opts_s {           /* structure describing run-time options */
 	bool no_splice;                /* flag set if never to use splice */
 	unsigned int skip_errors;      /* skip read errors counter */
 	bool stop_at_size;             /* set if we stop at "size" bytes */
+	bool sync_after_write;         /* set if we sync after every write */
 	double interval;               /* interval between updates */
 	double delay_start;            /* delay before first display */
 	unsigned int watch_pid;	       /* process to watch fds of */

src/include/pv-internal.h

@@ -93,6 +93,7 @@ struct pvstate_s {
 	bool no_op;                      /* do nothing other than pipe data */
 	unsigned int skip_errors;        /* skip read errors counter */
 	bool stop_at_size;               /* set if we stop at "size" bytes */
+	bool sync_after_write;           /* set if we sync after every write */
 	bool no_splice;                  /* never use splice() */
 	unsigned long long rate_limit;   /* rate limit, in bytes per second */
 	unsigned long long target_buffer_size;  /* buffer size (0=default) */

src/include/pv.h

@@ -106,6 +106,7 @@ extern void pv_state_null_set(pvstate_t, bool);
 extern void pv_state_no_op_set(pvstate_t, bool);
 extern void pv_state_skip_errors_set(pvstate_t, unsigned int);
 extern void pv_state_stop_at_size_set(pvstate_t, bool);
+extern void pv_state_sync_after_write_set(pvstate_t, bool);
 extern void pv_state_rate_limit_set(pvstate_t, unsigned long long);
 extern void pv_state_target_buffer_size_set(pvstate_t, unsigned long long);
 extern void pv_state_no_splice_set(pvstate_t, bool);