JSON output support for zpool list

This commit adds support for zpool list command to output the list of
ZFS pools in JSON format using '-j' option.. Information about available
pools is collected in nvlist which is later printed to stdout in JSON
format.

Existing options for zfs list command work with '-j' flag. man page for
zpool list is updated accordingly.

Reviewed-by: Tony Hutter <[email protected]>
Reviewed-by: Ameer Hamza <[email protected]>
Signed-off-by: Umer Saleem <[email protected]>
Closes #16217

2 files changed, 24 insertions, 0 deletions

diff --git a/lib/libspl/include/statcommon.h b/lib/libspl/include/statcommon.h
index 971997a44..d8d8fd684 100644
--- a/lib/libspl/include/statcommon.h
+++ b/lib/libspl/include/statcommon.h
@@ -37,5 +37,7 @@
 
 /* Print a timestamp in either Unix or standard format. */
 void print_timestamp(uint_t);
+/* Return timestamp in either Unix or standard format in provided buffer */
+void get_timestamp(uint_t, char *, int);
 
 #endif /* _STATCOMMON_H */
diff --git a/lib/libspl/timestamp.c b/lib/libspl/timestamp.c
index 9b435221f..8ab1a0e26 100644
--- a/lib/libspl/timestamp.c
+++ b/lib/libspl/timestamp.c
@@ -62,3 +62,25 @@ print_timestamp(uint_t timestamp_fmt)
 			(void) printf("%s\n", dstr);
 	}
 }
+
+/*
+ * Return timestamp as decimal reprentation (in string) of time_t
+ * value (-T u was specified) or in date(1) format (-T d was specified).
+ */
+void
+get_timestamp(uint_t timestamp_fmt, char *buf, int len)
+{
+	time_t t = time(NULL);
+	static const char *fmt = NULL;
+
+	/* We only need to retrieve this once per invocation */
+	if (fmt == NULL)
+		fmt = nl_langinfo(_DATE_FMT);
+
+	if (timestamp_fmt == UDATE) {
+		(void) snprintf(buf, len, "%lld", (longlong_t)t);
+	} else if (timestamp_fmt == DDATE) {
+		struct tm tm;
+		strftime(buf, len, fmt, localtime_r(&t, &tm));
+	}
+}