diff -burN tcsh-6.20.00.orig/sh.misc.c tcsh-6.20.00/sh.misc.c

--- tcsh-6.20.00.orig/sh.misc.c	2015-06-07 00:19:08.000000000 +0300

+++ tcsh-6.20.00/sh.misc.c	2017-07-20 16:09:31.517723814 +0300

@@ -257,6 +257,7 @@

 closem(void)

 {

     int f, num_files;

+    struct stat st;

 #ifdef NLS_BUGS

 #ifdef NLS_CATALOGS

@@ -271,6 +272,10 @@

     for (f = 0; f < num_files; f++)

 	if (f != SHIN && f != SHOUT && f != SHDIAG && f != OLDSTD &&

 	    f != FSHTTY 

+#ifdef S_ISSOCK

+	    /* Skip sockets: tcsh never creates them */

+	    && fstat(f, &st) == 0 && !S_ISSOCK(st.st_mode)

+#endif /* S_ISSOCK */

 #ifdef MALLOC_TRACE

 	    && f != 25

 #endif /* MALLOC_TRACE */