1 files changed, 5 insertions, 1 deletions
diff --git a/src/programs.asm b/src/programs.asm
index df2b98d..d4ae89f 100644
--- a/src/programs.asm
+++ b/src/programs.asm
@@ -59,8 +59,10 @@ ProgSh:
     ; read a line into SH_LINEBUF, echoing as we go
     ld hl, SH_LINEBUF
 .rd
+    push hl                     ; syscalls clobber HL (trap uses it to dispatch)
     ld c, SYS_READ
     rst $30                     ; A = input byte
+    pop hl
     cp $0D
     jr z, .eol
     cp $0A
@@ -70,7 +72,9 @@ ProgSh:
     ld [$FF01], a               ; echo the char straight to serial
     ld a, $81
     ld [$FF02], a
-    jr .rd
+    ld a, l
+    cp LOW(SH_LINEBUF) + SH_MAXLINE - 1
+    jr c, .rd                   ; keep reading unless the buffer is full
 
 .eol
     ld [hl], 0                  ; NUL-terminate