4 coloredstderr is a small library which uses 'LD_PRELOAD' to color stderr.
7 Like all solutions using 'LD_PRELOAD' it only works with dynamically linked
8 binaries. Statically linked binaries, for example valgrind, are not supported.
9 setuid binaries are also not supported ('LD_PRELOAD' disabled for security
13 It was inspired by stderred [2]. Similar solutions (using 'LD_PRELOAD')
16 - stderred [1], but doesn't `follow' dups (I somehow missed it when looking
17 for existing implementations)
18 - stderred [2], but only hooks `write()`
20 [1]: https://github.com/sickill/stderred
21 [2]: https://github.com/trapd00r/stderred
23 Most other existing solutions use a second process which colors its input and
24 pipe stderr to it. However this creates different runtime behaviour resulting
25 in a different ordering of the output. Partial lines (no newline) also often
32 - C99 compiler (variable length arrays)
33 - dynamic linker/loader which supports 'LD_PRELOAD' (e.g. GNU/Linux's ld.so)
39 ./configure && make && make check
41 Then either install the library with `make install` or just copy it from
42 `src/.libs/` to wherever you want to install it:
44 rm -f /destination/path/for/library/libcoloredstderr.so
45 cp -L src/.libs/libcoloredstderr.so /destination/path/for/library/
47 *Important:* If you install `libcoloredstderr.so` manually, make sure _not_ to
48 use plain `cp` to overwrite an existing `libcoloredstderr.so` file which is in
49 use! Doing so will crash most processes which were started with 'LD_PRELOAD'
50 set to this file. This is not a bug in coloredstderr, but a general problem.
51 `cp` truncates the file which causes the `mmap()` ed library to be in an
52 inconsistent state causing a segmentation fault when using any functions of
53 the library. Just remove the file first and then copy it. `make install`
54 handles the install in this way and is therefore not affected.
56 As a simple safeguard, `make` builds and installs the `libcoloredstderr.so`
57 file non-writable to prevent accidental overwrites. Even if the overwrite is
58 forced with `cp -f`, the file is unlinked and recreated by `cp` because the
59 file is non-writable, preventing the problem.
65 Set 'LD_PRELOAD' to include the _absolute_ path to `libcoloredstderr.so`:
67 LD_PRELOAD=/absolute/path/to/libcoloredstderr.so
69 The 'COLORED_STDERR_FDS' environment variable must be set to the file
70 descriptors which should be colored (comma separated list). Normally this is
75 The trailing comma is important!
78 A default setup could look like this:
80 LD_PRELOAD="$HOME/bin/libcoloredstderr.so"
82 export LD_PRELOAD COLORED_STDERR_FDS
85 The following additional environment variables are available:
87 - 'COLORED_STDERR_PRE'
88 String to write before each write to stderr, defaults to "\033[31m" (red).
89 - 'COLORED_STDERR_POST'
90 String to write after each write to stderr, defaults to "\033[0m" (reset
92 - 'COLORED_STDERR_FORCE_WRITE'
93 If set to an non-empty value add pre/post strings even when not writing to a
94 terminal, e.g. when writing to a file. By default, only writes to a terminal
96 - 'COLORED_STDERR_IGNORED_BINARIES'
97 Comma separated list of binary names/paths which should not be tracked
98 (including their children). Useful for `reset` which writes to the terminal
99 but fails to work if the output is colored. See below for an example.
101 All environment variables starting with 'COLORED_STDERR_PRIVATE_*' are
102 internal variables used by the implementation and should not be set manually.
103 See the source for details.
106 To set custom colors as pre/post strings you can use the `$''` feature of Bash
109 export COLORED_STDERR_PRE=$'\033[91m' # bright red
110 export COLORED_STDERR_POST=$'\033[0m' # default
112 Or to be more compatible you can use the following which should work in any
116 COLORED_STDERR_PRE="${esc}[91m" # red
117 COLORED_STDERR_POST="${esc}[0m" # default
118 export COLORED_STDERR_PRE COLORED_STDERR_POST
120 Fix `reset`; its writes to the terminal must be unaltered. `reset` is
121 symbolic-link to `tset` on some systems, adapt as necessary:
123 COLORED_STDERR_IGNORED_BINARIES=/usr/bin/tset
124 export COLORED_STDERR_IGNORED_BINARIES
130 To enable debug mode, configure coloredstderr with '--enable-debug'.
132 *Important:* Debug mode enables `assert()`s in the code which might abort the
133 process using 'LD_PRELOAD' if an error condition is detected!
135 Debug mode is slower than normal mode. To log only warnings without the
136 overhead of debug mode use '--enable-warnings'. `assert()`s are not enabled
137 with '--enable-warnings', so it's safe to use.
139 Debug messages are appended to the file `colored_stderr_debug_log.txt` in the
140 current working directory _if_ it exists. Be careful, this file might grow
143 *Important:* Warnings are written to `$HOME/colored_stderr_warning_log.txt`
144 even if it _does not_ exist (only if debug or warning mode is enabled)! If it
145 doesn't exist it's created. An existing file isn't overwritten, but the
146 warnings are appended at the end.
152 - `{fputc,putc,putchar}_unlocked()` are not hooked when writing to stdout
153 (which might be redirected to stderr). Can't be fixed as the compiler
154 inlines the code into the program without calling any function.
155 - Test `test_stdio.sh` fails for this reason on FreeBSD.
156 - 'COLORED_STDERR_IGNORED_BINARIES' requries the `/proc` file system.
163 If you find any bugs not mentioned in this document please report them to
164 <simon@ruderich.org> with coloredstderr in the subject.
170 Written by Simon Ruderich <simon@ruderich.org>.
176 coloredstderr is licensed under GPL version 3 or later.
178 Copyright (C) 2013 Simon Ruderich
180 This program is free software: you can redistribute it and/or modify
181 it under the terms of the GNU General Public License as published by
182 the Free Software Foundation, either version 3 of the License, or
183 (at your option) any later version.
185 This program is distributed in the hope that it will be useful,
186 but WITHOUT ANY WARRANTY; without even the implied warranty of
187 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
188 GNU General Public License for more details.
190 You should have received a copy of the GNU General Public License
191 along with this program. If not, see <http://www.gnu.org/licenses/>.