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 or
40 ./configure && make && make check
42 Then either install the library with `make install` or just copy it from
43 `src/.libs/` to wherever you want to install it:
45 rm -f /destination/path/for/library/libcoloredstderr.so
46 cp -L src/.libs/libcoloredstderr.so /destination/path/for/library/
48 *Important:* If you install `libcoloredstderr.so` manually, make sure _not_ to
49 use plain `cp` to overwrite an existing `libcoloredstderr.so` file which is in
50 use! Doing so will crash most processes which were started with 'LD_PRELOAD'
51 set to this file. This is not a bug in coloredstderr, but a general problem.
52 `cp` truncates the file which causes the `mmap()` ed library to be in an
53 inconsistent state causing a segmentation fault when using any functions of
54 the library. Just remove the file first and then copy it. `make install`
55 handles the install in this way and is therefore not affected.
57 As a simple safeguard, `make` builds and installs the `libcoloredstderr.so`
58 file non-writable to prevent accidental overwrites. Even if the overwrite is
59 forced with `cp -f`, the file is unlinked and recreated by `cp` because the
60 file is non-writable, preventing the problem.
66 Set 'LD_PRELOAD' to include the _absolute_ path to `libcoloredstderr.so`:
68 LD_PRELOAD=/absolute/path/to/libcoloredstderr.so
70 The 'COLORED_STDERR_FDS' environment variable must be set to the file
71 descriptors which should be colored (comma separated list). Normally this is
76 The trailing comma is important!
79 A default setup could look like this:
81 LD_PRELOAD="$HOME/bin/libcoloredstderr.so"
83 export LD_PRELOAD COLORED_STDERR_FDS
86 The following additional environment variables are available:
88 - 'COLORED_STDERR_PRE'
89 String to write before each write to stderr, defaults to "\033[31m" (red).
90 - 'COLORED_STDERR_POST'
91 String to write after each write to stderr, defaults to "\033[0m" (reset
93 - 'COLORED_STDERR_FORCE_WRITE'
94 If set to an non-empty value add pre/post strings even when not writing to a
95 terminal, e.g. when writing to a file. By default, only writes to a terminal
97 - 'COLORED_STDERR_IGNORED_BINARIES'
98 Comma separated list of binary names/paths which should not be tracked
99 (including their children). Useful for `reset` which writes to the terminal
100 but fails to work if the output is colored. See below for an example.
102 All environment variables starting with 'COLORED_STDERR_PRIVATE_*' are
103 internal variables used by the implementation and should not be set manually.
104 See the source for details.
107 To set custom colors as pre/post strings you can use the `$''` feature of Bash
110 export COLORED_STDERR_PRE=$'\033[91m' # bright red
111 export COLORED_STDERR_POST=$'\033[0m' # default
113 Or to be more compatible you can use the following which should work in any
117 COLORED_STDERR_PRE="${esc}[91m" # bright red
118 COLORED_STDERR_POST="${esc}[0m" # default
119 export COLORED_STDERR_PRE COLORED_STDERR_POST
121 Fix `reset`; its writes to the terminal must be unaltered. `reset` is a
122 symbolic-link to `tset` on some systems, adapt as necessary:
124 COLORED_STDERR_IGNORED_BINARIES=/usr/bin/tset
125 export COLORED_STDERR_IGNORED_BINARIES
131 To enable debug mode, configure coloredstderr with '--enable-debug'.
133 *Important:* Debug mode enables `assert()`s in the code which might abort the
134 process using 'LD_PRELOAD' if an error condition is detected!
136 Debug mode is slower than normal mode. To log only warnings without the
137 overhead of debug mode use '--enable-warnings'. `assert()`s are not enabled
138 with '--enable-warnings', so it's safe to use.
140 Debug messages are appended to the file `colored_stderr_debug_log.txt` in the
141 current working directory _if_ it exists. Be careful, this file might grow
144 *Important:* Warnings are written to `$HOME/colored_stderr_warning_log.txt`
145 even if it _does not_ exist (only if debug or warning mode is enabled)! If it
146 doesn't exist it's created. An existing file isn't overwritten, but the
147 warnings are appended at the end.
153 - `{fputc,putc,putchar}_unlocked()` are not hooked with glibc when writing to
154 stdout (which might be redirected to stderr). Can't be fixed as the compiler
155 inlines the code into the program without calling any function.
156 - Test `test_stdio.sh` fails on FreeBSD because FreeBSD does handle the above
157 correctly (no inlining), but the test is designed for GNU/Linux.
158 - 'COLORED_STDERR_IGNORED_BINARIES' requires the `/proc` file system.
160 - Output of `strace` is not always colored correctly as the output from
161 `coloredstderr` is traced and displayed as well.
167 If you find any bugs not mentioned in this document please report them to
168 <simon@ruderich.org> with coloredstderr in the subject.
174 Written by Simon Ruderich <simon@ruderich.org>.
180 coloredstderr is licensed under GPL version 3 or later.
182 Copyright (C) 2013 Simon Ruderich
184 This program is free software: you can redistribute it and/or modify
185 it under the terms of the GNU General Public License as published by
186 the Free Software Foundation, either version 3 of the License, or
187 (at your option) any later version.
189 This program is distributed in the hope that it will be useful,
190 but WITHOUT ANY WARRANTY; without even the implied warranty of
191 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
192 GNU General Public License for more details.
194 You should have received a copy of the GNU General Public License
195 along with this program. If not, see <http://www.gnu.org/licenses/>.