tr: fix "tr [=" case. Closes bug 4374.

function                                             old     new   delta
expand                                              1701    1738     +37
tr_main                                              472     474      +2

1 files changed, 2 insertions, 0 deletions

diff --git a/coreutils/tr.c b/coreutils/tr.c
index 28798fe4f..860b8122b 100644
--- a/coreutils/tr.c
+++ b/coreutils/tr.c
@@ -135,6 +135,8 @@ static unsigned int expand(const char *arg, char *buffer)
                         /* "[xyz...", i=x, arg points to y */
                         if (ENABLE_FEATURE_TR_EQUIV && i == '=') { /* [=CHAR=] */
                                 *buffer++ = *arg; /* copy CHAR */
+                                if (!*arg || arg[1] != '=' || arg[2] != ']')
+                                        bb_show_usage();
                                 arg += 3;       /* skip CHAR=] */
                                 continue;
                         }