Fix ARGF.read(length) short read [Bug #18074]

1 files changed, 1 insertions, 2 deletions

diff --git a/io.c b/io.c
index bbecc427db..4d5c3acd3a 100644
--- a/io.c
+++ b/io.c
@@ -12512,8 +12512,7 @@ argf_read(int argc, VALUE *argv, VALUE argf)
     else if (argc >= 1) {
 	long slen = RSTRING_LEN(str);
 	if (slen < len) {
-	    len -= slen;
-            argv[0] = LONG2NUM(len);
+            argv[0] = LONG2NUM(len - slen);
 	    goto retry;
 	}
     }