Re: the `--color' option of `ls' shadows the shortcut evaluation scheme of `&&' and `||'

[Jim Meyering]

Eric Blake <address@hidden> wrote:

> According to Day on 2/11/2008 8:35 PM:
> |
> |  [ "$(ls -A --color ./dir)" ] && echo "Not Empty" || echo "Empty"
> |
> | the echoed message is always "Not Empty", regardless of the fact that
> ./dir is actually EMPTY. Below is the tested result.
>
> Thanks for the report.  However, this is not necessarily a bug.  By
> itself, --color is documented to mean --color=always, in which case ls
> outputs command sequences to initialize and restore colors back to normal:
>
> $ ls -A --color | od -tx1z
> 0000000 1b 5b 30 6d 1b 5b 6d                             >.[0m.[m<
> 0000007
>
> And since that is output (even though it does not show up on the
> terminal), the string is non-empty, hence the result of the [] test.  You
> really want the color output to be supressed in this context (in $()
> command substitution, the output is not a terminal, so color escape
> sequences don't normally make sense to the downstream client), so you
> should consider using --color=auto instead:
>
> $ ls -A --color=auto | od -tx1z
> 0000000
>
> It may be worth considering a patch to coreutils, such that plain --color
> implies --color=auto rather than --color=always.  For example, this would
> match how 'git config' reacts when interpreting color options (where
> 'auto' and 'true' are synonyms, and 'always' must be explicit).

Sounds ok.
Any other opinions?

> It may also be worth a patch to ls to omit color sequences altogether if
> there is no other output, although this may be more difficult to code
> and/or justify.

Yes, that is worthwhile.
Ed Avis wrote a patch to do just that a few years ago.
It was held up due to copyright assignment processing delays,
and then I forgot about it.

I've just dug up the patch, merged it, and added one more test
along with the usual administrivia.

Here's the result I'll push in a day or two:

        ls --color no longer outputs unnecessary escape sequences
        In --color mode, plain files do not get any color, not even white.
        When no highlighting is required, ls outputs no escape sequence at all.
        * src/ls.c (print_with_color):
        (used_color): New global.
        (indicator_no) [C_RESET]: New enum value.
        (indicator_name) ["rs"]: Corresponding new string.
        (color_indicator): Make the 'normal' and 'file' markers be NULL.
        Use "rs" (C_RESET) to reset to ordinary colors.
        (process_signals): Restore default colors only if necessary.
        (main): Don't call prep_non_filename_text here.
        (print_name_with_quoting): Call it here, instead.
        (prep_non_filename_text): Use C_RESET, not C_NORM.
        (print_color_indicator): Return bool, not void.
        Print nothing, when possible.
        (put_indicator): Call prep_non_filename_text the first time.
        * tests/misc/ls-misc: Test for above.
        * tests/ls/color-dtype-dir: Adapt: no escapes around regular file name.
        * TODO: Remove item.
        * NEWS: Mention this.

Signed-off-by: Jim Meyering <address@hidden>
---
 NEWS                     |    4 +++
 TODO                     |    3 --
 src/ls.c                 |   60 +++++++++++++++++++++++++++++++++-------------
 tests/ls/color-dtype-dir |    4 +-
 tests/misc/ls-misc       |   17 ++++++++++--
 5 files changed, 63 insertions(+), 25 deletions(-)

diff --git a/NEWS b/NEWS
index e05e1c3..b9f25e6 100644
--- a/NEWS
+++ b/NEWS
@@ -10,6 +10,10 @@ GNU coreutils NEWS                                    -*- 
outline -*-
   "rmdir --ignore-fail-on-non-empty" detects and ignores the failure
   in more cases when a directory is empty.

+** Improvements
+
+  ls --color no longer outputs unnecessary escape sequences
+
 ** Consistency

   mkdir and split now write --verbose output to stdout, not stderr.
diff --git a/TODO b/TODO
index 3cec054..f8cc66a 100644
--- a/TODO
+++ b/TODO
@@ -133,9 +133,6 @@ Changes expected to go in, someday.

   Pending copyright papers:
   ------------------------
-  ls --color: Ed Avis' patch to suppress escape sequences for
-    non-highlighted files
-
   getpwnam from Bruce Korb

   pb (progress bar) from Miika Pekkarinen
diff --git a/src/ls.c b/src/ls.c
index 46713f2..bf94e8f 100644
--- a/src/ls.c
+++ b/src/ls.c
@@ -207,7 +207,7 @@ static bool file_ignored (char const *name);
 static uintmax_t gobble_file (char const *name, enum filetype type,
                              ino_t inode, bool command_line_arg,
                              char const *dirname);
-static void print_color_indicator (const char *name, mode_t mode, int linkok,
+static bool print_color_indicator (const char *name, mode_t mode, int linkok,
                                   bool stat_ok, enum filetype type);
 static void put_indicator (const struct bin_str *ind);
 static void add_ignore_pattern (const char *pattern);
@@ -489,6 +489,12 @@ ARGMATCH_VERIFY (indicator_style_args, 
indicator_style_types);

 static bool print_with_color;

+/* Whether we used any colors in the output so far.  If so, we will
+   need to restore the default color later.  If not, we will need to
+   call prep_non_filename_text before using color for the first time. */
+
+static bool used_color = false;
+
 enum color_type
   {
     color_never,               /* 0: default or --color=never */
@@ -507,14 +513,15 @@ enum Dereference_symlink

 enum indicator_no
   {
-    C_LEFT, C_RIGHT, C_END, C_NORM, C_FILE, C_DIR, C_LINK, C_FIFO, C_SOCK,
+    C_LEFT, C_RIGHT, C_END, C_RESET, C_NORM, C_FILE, C_DIR, C_LINK,
+    C_FIFO, C_SOCK,
     C_BLK, C_CHR, C_MISSING, C_ORPHAN, C_EXEC, C_DOOR, C_SETUID, C_SETGID,
     C_STICKY, C_OTHER_WRITABLE, C_STICKY_OTHER_WRITABLE
   };

 static const char *const indicator_name[]=
   {
-    "lc", "rc", "ec", "no", "fi", "di", "ln", "pi", "so",
+    "lc", "rc", "ec", "rs", "no", "fi", "di", "ln", "pi", "so",
     "bd", "cd", "mi", "or", "ex", "do", "su", "sg", "st",
     "ow", "tw", NULL
   };
@@ -531,8 +538,9 @@ static struct bin_str color_indicator[] =
     { LEN_STR_PAIR ("\033[") },                /* lc: Left of color sequence */
     { LEN_STR_PAIR ("m") },            /* rc: Right of color sequence */
     { 0, NULL },                       /* ec: End color (replaces lc+no+rc) */
-    { LEN_STR_PAIR ("0") },            /* no: Normal */
-    { LEN_STR_PAIR ("0") },            /* fi: File: default */
+    { LEN_STR_PAIR ("0") },            /* rs: Reset to ordinary colors */
+    { 0, NULL },                       /* no: Normal */
+    { 0, NULL },                       /* fi: File: default */
     { LEN_STR_PAIR ("01;34") },                /* di: Directory: bright blue */
     { LEN_STR_PAIR ("01;36") },                /* ln: Symlink: bright cyan */
     { LEN_STR_PAIR ("33") },           /* pi: Pipe: yellow/brown */
@@ -1072,7 +1080,8 @@ process_signals (void)
       int stops;
       sigset_t oldset;

-      restore_default_color ();
+      if (used_color)
+       restore_default_color ();
       fflush (stdout);

       sigprocmask (SIG_BLOCK, &caught_signals, &oldset);
@@ -1209,8 +1218,6 @@ main (int argc, char **argv)
            }
 #endif
        }
-
-      prep_non_filename_text ();
     }

   if (dereference == DEREF_UNDEFINED)
@@ -1325,7 +1332,8 @@ main (int argc, char **argv)
     {
       int j;

-      restore_default_color ();
+      if (used_color)
+       restore_default_color ();
       fflush (stdout);

       /* Restore the default signal handling.  */
@@ -3826,8 +3834,9 @@ print_name_with_quoting (const char *p, mode_t mode, int 
linkok,
                         bool stat_ok, enum filetype type,
                         struct obstack *stack)
 {
-  if (print_with_color)
-    print_color_indicator (p, mode, linkok, stat_ok, type);
+  bool used_color_this_time
+    = (print_with_color
+       && print_color_indicator (p, mode, linkok, stat_ok, type));

   if (stack)
     PUSH_CURRENT_DIRED_POS (stack);
@@ -3837,7 +3846,7 @@ print_name_with_quoting (const char *p, mode_t mode, int 
linkok,
   if (stack)
     PUSH_CURRENT_DIRED_POS (stack);

-  if (print_with_color)
+  if (used_color_this_time)
     {
       process_signals ();
       prep_non_filename_text ();
@@ -3852,7 +3861,7 @@ prep_non_filename_text (void)
   else
     {
       put_indicator (&color_indicator[C_LEFT]);
-      put_indicator (&color_indicator[C_NORM]);
+      put_indicator (&color_indicator[C_RESET]);
       put_indicator (&color_indicator[C_RIGHT]);
     }
 }
@@ -3927,7 +3936,8 @@ print_type_indicator (bool stat_ok, mode_t mode, enum 
filetype type)
     DIRED_PUTCHAR (c);
 }

-static void
+/* Returns whether any color sequence was printed. */
+static bool
 print_color_indicator (const char *name, mode_t mode, int linkok,
                       bool stat_ok, enum filetype filetype)
 {
@@ -4004,9 +4014,19 @@ print_color_indicator (const char *name, mode_t mode, 
int linkok,
        }
     }

-  put_indicator (&color_indicator[C_LEFT]);
-  put_indicator (ext ? &(ext->seq) : &color_indicator[type]);
-  put_indicator (&color_indicator[C_RIGHT]);
+  {
+    const struct bin_str *const s
+      = ext ? &(ext->seq) : &color_indicator[type];
+    if (s->string != NULL)
+      {
+       put_indicator (&color_indicator[C_LEFT]);
+       put_indicator (s);
+       put_indicator (&color_indicator[C_RIGHT]);
+       return true;
+      }
+    else
+      return false;
+  }
 }

 /* Output a color indicator (which may contain nulls).  */
@@ -4016,6 +4036,12 @@ put_indicator (const struct bin_str *ind)
   size_t i;
   const char *p;

+  if (! used_color)
+    {
+      used_color = true;
+      prep_non_filename_text ();
+    }
+
   p = ind->string;

   for (i = ind->len; i != 0; --i)
diff --git a/tests/ls/color-dtype-dir b/tests/ls/color-dtype-dir
index 7a25c06..b969701 100755
--- a/tests/ls/color-dtype-dir
+++ b/tests/ls/color-dtype-dir
@@ -4,7 +4,7 @@
 # directories the same as the first one -- but only on a file system
 # with dirent.d_type support.

-# Copyright (C) 2006-2007 Free Software Foundation, Inc.
+# Copyright (C) 2006-2008 Free Software Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -43,7 +43,7 @@ mv o1 out || fail=1
 cat <<\EOF > exp || fail=1
 ^[[0m^[[01;34md^[[0m$
 ^[[34;42mother-writable^[[0m$
-^[[0mout^[[0m$
+out$
 ^[[37;44msticky^[[0m$
 ^[[m
 EOF
diff --git a/tests/misc/ls-misc b/tests/misc/ls-misc
index 9290eb4..4182fa1 100755
--- a/tests/misc/ls-misc
+++ b/tests/misc/ls-misc
@@ -1,7 +1,7 @@
 #!/bin/sh
 # -*- perl -*-

-# Copyright (C) 1998, 2000-2007 Free Software Foundation, Inc.
+# Copyright (C) 1998, 2000-2008 Free Software Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -55,8 +55,14 @@ system (qq(touch setuid && chmod u+s setuid && $test -u 
setuid &&
   or (warn "$program_name: cannot create setuid/setgid/sticky files,"
       . "so can't run this test\n"), exit 77;

-my $mkdir = {PRE => sub {mkdir 'd',0755 or die "d: $!\n"}};
-my $rmdir = {POST => sub {rmdir 'd' or die "d: $!\n"}};
+sub mkdir_d {mkdir 'd',0755 or die "d: $!\n"}
+sub rmdir_d {rmdir 'd'      or die "d: $!\n"}
+my $mkdir = {PRE => sub {mkdir_d}};
+my $rmdir = {POST => sub {rmdir_d}};
+my $mkdir_reg = {PRE => sub {mkdir_d; open (FH, '>d/f') && close FH
+                              or die "d/f: $!\n" }};
+my $rmdir_reg = {POST => sub {unlink 'd/f' or die "d/f: $!\n";
+                             rmdir 'd' or die "d: $!\n"}};

 my $mkdir2 = {PRE => sub {mkdir 'd',0755 or die "d: $!\n";
                          mkdir 'd/e',0755 or die "d/e: $!\n" }};
@@ -132,6 +138,11 @@ my @Tests =
                                 {OUT => "\e[0m\e[01;address@hidden"},
                                  $slink_d, $unlink_d],

+     # A listing with no output should have no color sequences at all.
+     ['no-c-empty', '--color=always d', {OUT => ""}, $mkdir, $rmdir],
+     # A listing with only regular files should have no color sequences at all.
+     ['no-c-reg', '--color=always d', {OUT => "f\n"}, $mkdir_reg, $rmdir_reg],
+
      # Test for a bug fixed after coreutils-6.9.
      ['sl-target', '--color=always d',
       {OUT => "\e[0m\e[01;34mX\e[0m\n\e[m"}, $target, $target2],
--
1.5.4.1.98.gf3293


>From afeb251602c3d5ec9cffdadde25c4173dad498b0 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Tue, 12 Feb 2008 18:13:09 +0100
Subject: [PATCH] * src/ls.c (put_indicator): Use fwrite, not a loop.


Signed-off-by: Jim Meyering <address@hidden>
---
 src/ls.c |    8 +-------
 1 files changed, 1 insertions(+), 7 deletions(-)

diff --git a/src/ls.c b/src/ls.c
index bf94e8f..d5c6efb 100644
--- a/src/ls.c
+++ b/src/ls.c
@@ -4033,19 +4033,13 @@ print_color_indicator (const char *name, mode_t mode, 
int linkok,
 static void
 put_indicator (const struct bin_str *ind)
 {
-  size_t i;
-  const char *p;
-
   if (! used_color)
     {
       used_color = true;
       prep_non_filename_text ();
     }

-  p = ind->string;
-
-  for (i = ind->len; i != 0; --i)
-    putchar (*(p++));
+  fwrite (ind->string, ind->len, 1, stdout);
 }

 static size_t
--
1.5.4.1.98.gf3293