ls: don't output any colors with TERM=dumb

The TERM variable is usually set to "dumb" to indicate that the terminal
does not support any ANSI escape sequences. Presently, ls does not honor
this variable and outputs colors anyhow which results in unreadable
output, unless the user explicitly disables colors using `ls
--color=never`. The rational behind this change is that ls should "just
work" by default, even on dumb terminals.

For this reason, this patch adds a check which additionally consults the
TERM variable before printing any colors. This is analogous to the
existing check for ensuring that standard output is a tty. As such,
colors can still be forced with `--color=force`, even if TERM is set to
dumb.

function                                             old     new   delta
is_TERM_dumb                                           -      40     +40
ls_main                                              579     598     +19
.rodata                                           103246  103251      +5
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 2/0 up/down: 64/0)               Total: 64 bytes

Signed-off-by: Sören Tempel <soeren+git@soeren-tempel.net>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/libbb/xfuncs.c b/libbb/xfuncs.c
index d93d8aaf5..c81ce4546 100644
--- a/libbb/xfuncs.c
+++ b/libbb/xfuncs.c
@@ -303,6 +303,12 @@ int FAST_FUNC get_terminal_width(int fd)
 	return width;
 }
 
+int FAST_FUNC is_dumb_term(void)
+{
+	char *term = getenv("TERM");
+	return term && strcmp(term, "dumb") == 0;
+}
+
 int FAST_FUNC tcsetattr_stdin_TCSANOW(const struct termios *tp)
 {
 	return tcsetattr(STDIN_FILENO, TCSANOW, tp);