Use setproctitle to report progress of zfs send

This allows parsing of zfs send progress by checking the process
title.
Doing so requires some changes to the send code in libzfs_sendrecv.c;
primarily these changes move some of the accounting around, to allow
for the code to be verbose as normal, or set the process title. Unlike
BSD, setproctitle() isn't standard in Linux; thus, borrowed it from
libbsd with slight modifications.

Authored-by: Sean Eric Fagan <[email protected]>
Co-authored-by: Ryan Moeller <[email protected]>
Co-authored-by: Ameer Hamza <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Ryan Moeller <[email protected]>
Signed-off-by: Ameer Hamza <[email protected]>
Closes #14376 

4 files changed, 361 insertions, 15 deletions

diff --git a/lib/libzfs/libzfs.abi b/lib/libzfs/libzfs.abi
index e5115e973..004930e34 100644
--- a/lib/libzfs/libzfs.abi
+++ b/lib/libzfs/libzfs.abi
@@ -416,6 +416,8 @@
     <elf-symbol name='zfs_send_resume_token_to_nvlist' type='func-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfs_send_saved' type='func-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfs_set_fsacl' type='func-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
+    <elf-symbol name='zfs_setproctitle' type='func-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
+    <elf-symbol name='zfs_setproctitle_init' type='func-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfs_share' type='func-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfs_show_diffs' type='func-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
     <elf-symbol name='zfs_smb_acl_add' type='func-type' binding='global-binding' visibility='default-visibility' is-defined='yes'/>
@@ -3834,6 +3836,11 @@
     <pointer-type-def type-id='9e59d1d4' size-in-bits='64' id='4ea84b4f'/>
     <pointer-type-def type-id='945467e6' size-in-bits='64' id='8def7735'/>
     <pointer-type-def type-id='3d3ffb69' size-in-bits='64' id='72a26210'/>
+    <function-decl name='zfs_setproctitle' mangled-name='zfs_setproctitle' visibility='default' binding='global' size-in-bits='64' elf-symbol-id='zfs_setproctitle'>
+      <parameter type-id='80f4b756'/>
+      <parameter is-variadic='yes'/>
+      <return type-id='48b5725f'/>
+    </function-decl>
     <function-decl name='zfs_send_progress' mangled-name='zfs_send_progress' visibility='default' binding='global' size-in-bits='64' elf-symbol-id='zfs_send_progress'>
       <parameter type-id='9200a744' name='zhp'/>
       <parameter type-id='95e97e5e' name='fd'/>
@@ -4525,6 +4532,12 @@
       <parameter type-id='5ce45b60' name='nv'/>
       <return type-id='48b5725f'/>
     </function-decl>
+    <function-decl name='zfs_setproctitle_init' mangled-name='zfs_setproctitle_init' visibility='default' binding='global' size-in-bits='64' elf-symbol-id='zfs_setproctitle_init'>
+      <parameter type-id='95e97e5e' name='argc'/>
+      <parameter type-id='9b23c9ad' name='argv'/>
+      <parameter type-id='9b23c9ad' name='envp'/>
+      <return type-id='48b5725f'/>
+    </function-decl>
   </abi-instr>
   <abi-instr address-size='64' path='lib/libzutil/zutil_device_path.c' language='LANG_C99'>
     <typedef-decl name='ssize_t' type-id='41060289' id='79a0948f'/>
diff --git a/lib/libzfs/libzfs_sendrecv.c b/lib/libzfs/libzfs_sendrecv.c
index c79c636e1..7aebd85f8 100644
--- a/lib/libzfs/libzfs_sendrecv.c
+++ b/lib/libzfs/libzfs_sendrecv.c
@@ -83,6 +83,8 @@ typedef struct progress_arg {
 	boolean_t pa_parsable;
 	boolean_t pa_estimate;
 	int pa_verbosity;
+	boolean_t pa_astitle;
+	uint64_t pa_size;
 } progress_arg_t;
 
 static int
@@ -733,6 +735,7 @@ typedef struct send_dump_data {
 	boolean_t seenfrom, seento, replicate, doall, fromorigin;
 	boolean_t dryrun, parsable, progress, embed_data, std_out;
 	boolean_t large_block, compress, raw, holds;
+	boolean_t progressastitle;
 	int outfd;
 	boolean_t err;
 	nvlist_t *fss;
@@ -931,12 +934,13 @@ send_progress_thread(void *arg)
 	zfs_handle_t *zhp = pa->pa_zhp;
 	uint64_t bytes;
 	uint64_t blocks;
+	uint64_t total = pa->pa_size / 100;
 	char buf[16];
 	time_t t;
 	struct tm tm;
 	int err;
 
-	if (!pa->pa_parsable) {
+	if (!pa->pa_parsable && pa->pa_verbosity != 0) {
 		(void) fprintf(stderr,
 		    "TIME       %s   %sSNAPSHOT %s\n",
 		    pa->pa_estimate ? "BYTES" : " SENT",
@@ -959,6 +963,17 @@ send_progress_thread(void *arg)
 		(void) time(&t);
 		localtime_r(&t, &tm);
 
+		if (pa->pa_astitle) {
+			char buf_bytes[16];
+			char buf_size[16];
+			int pct;
+			zfs_nicenum(bytes, buf_bytes, sizeof (buf_bytes));
+			zfs_nicenum(pa->pa_size, buf_size, sizeof (buf_size));
+			pct = (total > 0) ? bytes / total : 100;
+			zfs_setproctitle("sending %s (%d%%: %s/%s)",
+			    zhp->zfs_name, MIN(pct, 100), buf_bytes, buf_size);
+		}
+
 		if (pa->pa_verbosity >= 2 && pa->pa_parsable) {
 			(void) fprintf(stderr,
 			    "%02d:%02d:%02d\t%llu\t%llu\t%s\n",
@@ -975,7 +990,7 @@ send_progress_thread(void *arg)
 			(void) fprintf(stderr, "%02d:%02d:%02d\t%llu\t%s\n",
 			    tm.tm_hour, tm.tm_min, tm.tm_sec,
 			    (u_longlong_t)bytes, zhp->zfs_name);
-		} else {
+		} else if (pa->pa_verbosity != 0) {
 			zfs_nicebytes(bytes, buf, sizeof (buf));
 			(void) fprintf(stderr, "%02d:%02d:%02d   %5s   %s\n",
 			    tm.tm_hour, tm.tm_min, tm.tm_sec,
@@ -1183,12 +1198,14 @@ dump_snapshot(zfs_handle_t *zhp, void *arg)
 		 * If progress reporting is requested, spawn a new thread to
 		 * poll ZFS_IOC_SEND_PROGRESS at a regular interval.
 		 */
-		if (sdd->progress) {
+		if (sdd->progress || sdd->progressastitle) {
 			pa.pa_zhp = zhp;
 			pa.pa_fd = sdd->outfd;
 			pa.pa_parsable = sdd->parsable;
 			pa.pa_estimate = B_FALSE;
 			pa.pa_verbosity = sdd->verbosity;
+			pa.pa_size = sdd->size;
+			pa.pa_astitle = sdd->progressastitle;
 
 			if ((err = pthread_create(&tid, NULL,
 			    send_progress_thread, &pa)) != 0) {
@@ -1200,7 +1217,7 @@ dump_snapshot(zfs_handle_t *zhp, void *arg)
 		err = dump_ioctl(zhp, sdd->prevsnap, sdd->prevsnap_obj,
 		    fromorigin, sdd->outfd, flags, sdd->debugnv);
 
-		if (sdd->progress &&
+		if ((sdd->progress || sdd->progressastitle) &&
 		    send_progress_thread_exit(zhp->zfs_hdl, tid))
 			return (-1);
 	}
@@ -1536,7 +1553,7 @@ lzc_flags_from_sendflags(const sendflags_t *flags)
 static int
 estimate_size(zfs_handle_t *zhp, const char *from, int fd, sendflags_t *flags,
     uint64_t resumeobj, uint64_t resumeoff, uint64_t bytes,
-    const char *redactbook, char *errbuf)
+    const char *redactbook, char *errbuf, uint64_t *sizep)
 {
 	uint64_t size;
 	FILE *fout = flags->dryrun ? stdout : stderr;
@@ -1544,7 +1561,7 @@ estimate_size(zfs_handle_t *zhp, const char *from, int fd, sendflags_t *flags,
 	int err = 0;
 	pthread_t ptid;
 
-	if (flags->progress) {
+	if (flags->progress || flags->progressastitle) {
 		pa.pa_zhp = zhp;
 		pa.pa_fd = fd;
 		pa.pa_parsable = flags->parsable;
@@ -1563,10 +1580,15 @@ estimate_size(zfs_handle_t *zhp, const char *from, int fd, sendflags_t *flags,
 	err = lzc_send_space_resume_redacted(zhp->zfs_name, from,
 	    lzc_flags_from_sendflags(flags), resumeobj, resumeoff, bytes,
 	    redactbook, fd, &size);
+	*sizep = size;
 
-	if (flags->progress && send_progress_thread_exit(zhp->zfs_hdl, ptid))
+	if ((flags->progress || flags->progressastitle) &&
+	    send_progress_thread_exit(zhp->zfs_hdl, ptid))
 		return (-1);
 
+	if (!flags->progress && !flags->parsable)
+		return (err);
+
 	if (err != 0) {
 		zfs_error_aux(zhp->zfs_hdl, "%s", strerror(err));
 		return (zfs_error(zhp->zfs_hdl, EZFS_BADBACKUP,
@@ -1743,6 +1765,7 @@ zfs_send_resume_impl_cb_impl(libzfs_handle_t *hdl, sendflags_t *flags,
 	uint64_t *redact_snap_guids = NULL;
 	int num_redact_snaps = 0;
 	char *redact_book = NULL;
+	uint64_t size = 0;
 
 	(void) snprintf(errbuf, sizeof (errbuf), dgettext(TEXT_DOMAIN,
 	    "cannot resume send"));
@@ -1828,7 +1851,7 @@ zfs_send_resume_impl_cb_impl(libzfs_handle_t *hdl, sendflags_t *flags,
 	enum lzc_send_flags lzc_flags = lzc_flags_from_sendflags(flags) |
 	    lzc_flags_from_resume_nvl(resume_nvl);
 
-	if (flags->verbosity != 0) {
+	if (flags->verbosity != 0 || flags->progressastitle) {
 		/*
 		 * Some of these may have come from the resume token, set them
 		 * here for size estimate purposes.
@@ -1845,7 +1868,7 @@ zfs_send_resume_impl_cb_impl(libzfs_handle_t *hdl, sendflags_t *flags,
 		if (lzc_flags & LZC_SEND_FLAG_SAVED)
 			tmpflags.saved = B_TRUE;
 		error = estimate_size(zhp, fromname, outfd, &tmpflags,
-		    resumeobj, resumeoff, bytes, redact_book, errbuf);
+		    resumeobj, resumeoff, bytes, redact_book, errbuf, &size);
 	}
 
 	if (!flags->dryrun) {
@@ -1855,12 +1878,14 @@ zfs_send_resume_impl_cb_impl(libzfs_handle_t *hdl, sendflags_t *flags,
 		 * If progress reporting is requested, spawn a new thread to
 		 * poll ZFS_IOC_SEND_PROGRESS at a regular interval.
 		 */
-		if (flags->progress) {
+		if (flags->progress || flags->progressastitle) {
 			pa.pa_zhp = zhp;
 			pa.pa_fd = outfd;
 			pa.pa_parsable = flags->parsable;
 			pa.pa_estimate = B_FALSE;
 			pa.pa_verbosity = flags->verbosity;
+			pa.pa_size = size;
+			pa.pa_astitle = flags->progressastitle;
 
 			error = pthread_create(&tid, NULL,
 			    send_progress_thread, &pa);
@@ -1877,8 +1902,11 @@ zfs_send_resume_impl_cb_impl(libzfs_handle_t *hdl, sendflags_t *flags,
 		if (redact_book != NULL)
 			free(redact_book);
 
-		if (flags->progress && send_progress_thread_exit(hdl, tid))
+		if ((flags->progressastitle || flags->progress) &&
+		    send_progress_thread_exit(hdl, tid)) {
+			zfs_close(zhp);
 			return (-1);
+		}
 
 		char errbuf[ERRBUFLEN];
 		(void) snprintf(errbuf, sizeof (errbuf), dgettext(TEXT_DOMAIN,
@@ -2313,6 +2341,7 @@ zfs_send_cb_impl(zfs_handle_t *zhp, const char *fromsnap, const char *tosnap,
 	sdd.verbosity = flags->verbosity;
 	sdd.parsable = flags->parsable;
 	sdd.progress = flags->progress;
+	sdd.progressastitle = flags->progressastitle;
 	sdd.dryrun = flags->dryrun;
 	sdd.large_block = flags->largeblock;
 	sdd.embed_data = flags->embed_data;
@@ -2562,6 +2591,7 @@ zfs_send_one_cb_impl(zfs_handle_t *zhp, const char *from, int fd,
 	char *name = zhp->zfs_name;
 	pthread_t ptid;
 	progress_arg_t pa = { 0 };
+	uint64_t size = 0;
 
 	char errbuf[ERRBUFLEN];
 	(void) snprintf(errbuf, sizeof (errbuf), dgettext(TEXT_DOMAIN,
@@ -2644,9 +2674,9 @@ zfs_send_one_cb_impl(zfs_handle_t *zhp, const char *from, int fd,
 	/*
 	 * Perform size estimate if verbose was specified.
 	 */
-	if (flags->verbosity != 0) {
+	if (flags->verbosity != 0 || flags->progressastitle) {
 		err = estimate_size(zhp, from, fd, flags, 0, 0, 0, redactbook,
-		    errbuf);
+		    errbuf, &size);
 		if (err != 0)
 			return (err);
 	}
@@ -2658,12 +2688,14 @@ zfs_send_one_cb_impl(zfs_handle_t *zhp, const char *from, int fd,
 	 * If progress reporting is requested, spawn a new thread to poll
 	 * ZFS_IOC_SEND_PROGRESS at a regular interval.
 	 */
-	if (flags->progress) {
+	if (flags->progress || flags->progressastitle) {
 		pa.pa_zhp = zhp;
 		pa.pa_fd = fd;
 		pa.pa_parsable = flags->parsable;
 		pa.pa_estimate = B_FALSE;
 		pa.pa_verbosity = flags->verbosity;
+		pa.pa_size = size;
+		pa.pa_astitle = flags->progressastitle;
 
 		err = pthread_create(&ptid, NULL,
 		    send_progress_thread, &pa);
@@ -2677,7 +2709,8 @@ zfs_send_one_cb_impl(zfs_handle_t *zhp, const char *from, int fd,
 	err = lzc_send_redacted(name, from, fd,
 	    lzc_flags_from_sendflags(flags), redactbook);
 
-	if (flags->progress && send_progress_thread_exit(hdl, ptid))
+	if ((flags->progress || flags->progressastitle) &&
+	    send_progress_thread_exit(hdl, ptid))
 			return (-1);
 
 	if (err == 0 && (flags->props || flags->holds || flags->backup)) {
diff --git a/lib/libzutil/Makefile.am b/lib/libzutil/Makefile.am
index ecdf94050..519906235 100644
--- a/lib/libzutil/Makefile.am
+++ b/lib/libzutil/Makefile.am
@@ -17,6 +17,7 @@ libzutil_la_SOURCES = \
 
 if BUILD_LINUX
 libzutil_la_SOURCES += \
+	%D%/os/linux/zutil_setproctitle.c \
 	%D%/os/linux/zutil_device_path_os.c \
 	%D%/os/linux/zutil_import_os.c
 endif
diff --git a/lib/libzutil/os/linux/zutil_setproctitle.c b/lib/libzutil/os/linux/zutil_setproctitle.c
new file mode 100644
index 000000000..4a6d12cf7
--- /dev/null
+++ b/lib/libzutil/os/linux/zutil_setproctitle.c
@@ -0,0 +1,299 @@
+/*
+ * Copyright © 2013 Guillem Jover <[email protected]>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
+ * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <errno.h>
+#include <stddef.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <err.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/param.h>
+#include <libzutil.h>
+
+static struct {
+	/* Original value. */
+	const char *arg0;
+
+	/* Title space available. */
+	char *base, *end;
+
+	/* Pointer to original nul character within base. */
+	char *nul;
+
+	boolean_t warned;
+	boolean_t reset;
+	int error;
+} SPT;
+
+#define	LIBBSD_IS_PATHNAME_SEPARATOR(c) ((c) == '/')
+#define	SPT_MAXTITLE 255
+
+extern const char *__progname;
+
+static const char *
+getprogname(void)
+{
+	return (__progname);
+}
+
+static void
+setprogname(const char *progname)
+{
+	size_t i;
+
+	for (i = strlen(progname); i > 0; i--) {
+		if (LIBBSD_IS_PATHNAME_SEPARATOR(progname[i - 1])) {
+			__progname = progname + i;
+			return;
+		}
+	}
+	__progname = progname;
+}
+
+
+static inline size_t
+spt_min(size_t a, size_t b)
+{
+	return ((a < b) ? a : b);
+}
+
+/*
+ * For discussion on the portability of the various methods, see
+ * https://lists.freebsd.org/pipermail/freebsd-stable/2008-June/043136.html
+ */
+static int
+spt_clearenv(void)
+{
+	char **tmp;
+
+	tmp = malloc(sizeof (*tmp));
+	if (tmp == NULL)
+		return (errno);
+
+	tmp[0] = NULL;
+	environ = tmp;
+
+	return (0);
+}
+
+static int
+spt_copyenv(int envc, char *envp[])
+{
+	char **envcopy;
+	char *eq;
+	int envsize;
+	int i, error;
+
+	if (environ != envp)
+		return (0);
+
+	/*
+	 * Make a copy of the old environ array of pointers, in case
+	 * clearenv() or setenv() is implemented to free the internal
+	 * environ array, because we will need to access the old environ
+	 * contents to make the new copy.
+	 */
+	envsize = (envc + 1) * sizeof (char *);
+	envcopy = malloc(envsize);
+	if (envcopy == NULL)
+		return (errno);
+	memcpy(envcopy, envp, envsize);
+
+	error = spt_clearenv();
+	if (error) {
+		environ = envp;
+		free(envcopy);
+		return (error);
+	}
+
+	for (i = 0; envcopy[i]; i++) {
+		eq = strchr(envcopy[i], '=');
+		if (eq == NULL)
+			continue;
+
+		*eq = '\0';
+		if (setenv(envcopy[i], eq + 1, 1) < 0)
+			error = errno;
+		*eq = '=';
+
+		if (error) {
+			environ = envp;
+			free(envcopy);
+			return (error);
+		}
+	}
+
+	/*
+	 * Dispose of the shallow copy, now that we've finished transfering
+	 * the old environment.
+	 */
+	free(envcopy);
+
+	return (0);
+}
+
+static int
+spt_copyargs(int argc, char *argv[])
+{
+	char *tmp;
+	int i;
+
+	for (i = 1; i < argc || (i >= argc && argv[i]); i++) {
+		if (argv[i] == NULL)
+			continue;
+
+		tmp = strdup(argv[i]);
+		if (tmp == NULL)
+			return (errno);
+
+		argv[i] = tmp;
+	}
+
+	return (0);
+}
+
+void
+zfs_setproctitle_init(int argc, char *argv[], char *envp[])
+{
+	char *base, *end, *nul, *tmp;
+	int i, envc, error;
+
+	/* Try to make sure we got called with main() arguments. */
+	if (argc < 0)
+		return;
+
+	base = argv[0];
+	if (base == NULL)
+		return;
+
+	nul = base + strlen(base);
+	end = nul + 1;
+
+	for (i = 0; i < argc || (i >= argc && argv[i]); i++) {
+		if (argv[i] == NULL || argv[i] != end)
+			continue;
+
+		end = argv[i] + strlen(argv[i]) + 1;
+	}
+
+	for (i = 0; envp[i]; i++) {
+		if (envp[i] != end)
+			continue;
+
+		end = envp[i] + strlen(envp[i]) + 1;
+	}
+	envc = i;
+
+	SPT.arg0 = strdup(argv[0]);
+	if (SPT.arg0 == NULL) {
+		SPT.error = errno;
+		return;
+	}
+
+	tmp = strdup(getprogname());
+	if (tmp == NULL) {
+		SPT.error = errno;
+		return;
+	}
+	setprogname(tmp);
+
+	error = spt_copyenv(envc, envp);
+	if (error) {
+		SPT.error = error;
+		return;
+	}
+
+	error = spt_copyargs(argc, argv);
+	if (error) {
+		SPT.error = error;
+		return;
+	}
+
+	SPT.nul  = nul;
+	SPT.base = base;
+	SPT.end  = end;
+}
+
+void
+zfs_setproctitle(const char *fmt, ...)
+{
+	/* Use buffer in case argv[0] is passed. */
+	char buf[SPT_MAXTITLE + 1];
+	va_list ap;
+	char *nul;
+	int len;
+	if (SPT.base == NULL) {
+		if (!SPT.warned) {
+			warnx("setproctitle not initialized, please"
+			    "call zfs_setproctitle_init()");
+			SPT.warned = B_TRUE;
+		}
+		return;
+	}
+
+	if (fmt) {
+		if (fmt[0] == '-') {
+			/* Skip program name prefix. */
+			fmt++;
+			len = 0;
+		} else {
+			/* Print program name heading for grep. */
+			snprintf(buf, sizeof (buf), "%s: ", getprogname());
+			len = strlen(buf);
+		}
+
+		va_start(ap, fmt);
+		len += vsnprintf(buf + len, sizeof (buf) - len, fmt, ap);
+		va_end(ap);
+	} else {
+		len = snprintf(buf, sizeof (buf), "%s", SPT.arg0);
+	}
+
+	if (len <= 0) {
+		SPT.error = errno;
+		return;
+	}
+
+	if (!SPT.reset) {
+		memset(SPT.base, 0, SPT.end - SPT.base);
+		SPT.reset = B_TRUE;
+	} else {
+		memset(SPT.base, 0, spt_min(sizeof (buf), SPT.end - SPT.base));
+	}
+
+	len = spt_min(len, spt_min(sizeof (buf), SPT.end - SPT.base) - 1);
+	memcpy(SPT.base, buf, len);
+	nul = SPT.base + len;
+
+	if (nul < SPT.nul) {
+		*SPT.nul = '.';
+	} else if (nul == SPT.nul && nul + 1 < SPT.end) {
+		*SPT.nul = ' ';
+		*++nul = '\0';
+	}
+}