-q controls output for filenames. From ls.c: /* True means output nongraphic chars in file names as '?'. (-q, --hide-control-chars) qmark_funny_chars and the quoting style (-Q, --quoting-style=WORD) are independent. The algorithm is: first, obey the quoting style to get a string representing the file name; then, if qmark_funny_chars is set, replace all nonprintable chars in that string with '?'. It's necessary to replace nonprintable chars even in quoted strings, because we don't want to mess up the terminal if control chars get sent to it, and some quoting methods pass through control chars as-is. */ static bool qmark_funny_chars;