2 files changed, 9 insertions, 3 deletions

diff --git a/usr.bin/xargs/xargs.1 b/usr.bin/xargs/xargs.1
index bba7aa24ecbe..7c2f70bd3959 100644
--- a/usr.bin/xargs/xargs.1
+++ b/usr.bin/xargs/xargs.1
@@ -211,6 +211,9 @@ No commands are executed if the process is not attached to a terminal.
 Specify the maximum number of arguments that
 .Fl I
 will do replacement in.
+If
+.Ar replacements
+is negative, the number of arguments in which to replace is unbounded.
 .It Fl s Ar size
 Set the maximum number of bytes for the command line length provided to
 .Ar utility .
diff --git a/usr.bin/xargs/xargs.c b/usr.bin/xargs/xargs.c
index 7dc859cee8b4..ec15af7555bc 100644
--- a/usr.bin/xargs/xargs.c
+++ b/usr.bin/xargs/xargs.c
@@ -96,6 +96,7 @@ main(int argc, char *argv[])
 	long arg_max;
 	int ch, Jflag, nargs, nflag, nline;
 	size_t linelen;
+	char *endptr;
 
 	inpline = replstr = NULL;
 	ep = environ;
@@ -158,8 +159,9 @@ main(int argc, char *argv[])
 			pflag = 1;
 			break;
 		case 'R':
-			if ((Rflag = atoi(optarg)) <= 0)
-				errx(1, "illegal number of replacements");
+			Rflag = strtol(optarg, &endptr, 10);
+			if (*endptr != '\0')
+				errx(1, "replacements must be a number");
 			break;
 		case 's':
 			nline = atoi(optarg);
@@ -444,7 +446,8 @@ prerun(int argc, char *argv[])
 		*tmp = *avj++;
 		if (repls && strstr(*tmp, replstr) != NULL) {
 			strnsubst(tmp++, replstr, inpline, (size_t)255);
-			repls--;
+			if (repls > 0)
+				repls--;
 		} else {
 			if ((*tmp = strdup(*tmp)) == NULL)
 				errx(1, "strdup failed");