README
======
-coloredstderr is a small library which uses 'LD_PRELOAD' to color stderr.
+coloredstderr is a small library which uses 'LD_PRELOAD' to color stderr. It
+``follows'' dups, has minimal performance overhead and can ignore certain
+binaries (requires /proc).
Like all solutions using 'LD_PRELOAD' it only works with dynamically linked
binaries. Statically linked binaries, for example valgrind, are not supported.
+setuid binaries are also not supported ('LD_PRELOAD' disabled for security
+reasons).
It was inspired by stderred [2]. Similar solutions (using 'LD_PRELOAD')
Most other existing solutions use a second process which colors its input and
pipe stderr to it. However this creates different runtime behaviour resulting
in a different ordering of the output. Partial lines (no newline) also often
-cause problems.
+cause problems. coloredstderr handles these cases correctly.
+
+coloredstderr is licensed under GPL 3 (or later).
DEPENDENCIES
------------
- C99 compiler (variable length arrays)
-- dynamic linker/loader which supports 'LD_PRELOAD' (e.g. GNU/Linux's ld.so)
+- dynamic linker/loader which supports 'LD_PRELOAD' (e.g. GNU/Linux's or
+ FreeBSD's ld.so)
+
+
+INSTALLATION
+------------
+
+ ./configure && make && make check
+
+Then either install the library with `make install` or just copy it from
+`src/.libs/` to wherever you want to install it:
+
+ rm -f /destination/path/for/library/libcoloredstderr.so
+ cp -L src/.libs/libcoloredstderr.so /destination/path/for/library/
+
+*Important:* If you install `libcoloredstderr.so` manually, make sure _not_ to
+use plain `cp` to overwrite an existing `libcoloredstderr.so` file which is in
+use! Doing so will crash most processes which were started with 'LD_PRELOAD'
+set to this file. This is not a bug in coloredstderr, but a general problem.
+`cp` truncates the file which causes the `mmap()` ed library to be in an
+inconsistent state causing a segmentation fault when using any functions of
+the library. Just remove the file first and then copy it. `make install`
+handles the install in this way and is therefore not affected.
+
+As a simple safeguard, `make` builds and installs the `libcoloredstderr.so`
+file non-writable to prevent accidental overwrites. Even if the overwrite is
+forced with `cp -f`, the file is unlinked and recreated by `cp` because the
+file is non-writable, preventing the problem.
USAGE
The following additional environment variables are available:
- 'COLORED_STDERR_PRE'
- String to write before each write to stderr, defaults to "\033[91m" (bright
- red).
+ String to write before each write to stderr, defaults to "\033[31m" (red).
- 'COLORED_STDERR_POST'
String to write after each write to stderr, defaults to "\033[0m" (reset
color).
If set to an non-empty value add pre/post strings even when not writing to a
terminal, e.g. when writing to a file. By default, only writes to a terminal
are colored.
+- 'COLORED_STDERR_IGNORED_BINARIES'
+ Comma separated list of binary names/paths which should not be tracked
+ (including their children). Useful for `reset` which writes to the terminal
+ but fails to work if the output is colored. See below for an example.
+
+All environment variables starting with 'COLORED_STDERR_PRIVATE_*' are
+internal variables used by the implementation and should not be set manually.
+See the source for details.
+
+
+To set custom colors as pre/post strings you can use the `$''` feature of Bash
+and Zsh:
+
+ export COLORED_STDERR_PRE=$'\033[91m' # bright red
+ export COLORED_STDERR_POST=$'\033[0m' # default
+
+Or to be more compatible you can use the following which should work in any
+Bourne shell:
+
+ esc=`printf '\033'`
+ COLORED_STDERR_PRE="${esc}[91m" # bright red
+ COLORED_STDERR_POST="${esc}[0m" # default
+ export COLORED_STDERR_PRE COLORED_STDERR_POST
+
+Fix `reset`; its writes to the terminal must be unaltered. `reset` is a
+symbolic-link to `tset` on some systems, adapt as necessary:
+
+ COLORED_STDERR_IGNORED_BINARIES=/usr/bin/tset
+ export COLORED_STDERR_IGNORED_BINARIES
DEBUG
To enable debug mode, configure coloredstderr with '--enable-debug'.
+*Important:* Debug mode enables `assert()`s in the code which might abort the
+process using 'LD_PRELOAD' if an error condition is detected!
+
Debug mode is slower than normal mode. To log only warnings without the
-overhead of debug mode use '--enable-warnings'.
+overhead of debug mode use '--enable-warnings'. `assert()`s are not enabled
+with '--enable-warnings', so it's safe to use.
-Debug messages are written to the file `colored_stderr_debug_log.txt` in the
-current working directory _if_ it exists. If it exists debug messages are
-appended. Be careful, this file might grow very quickly.
+Debug messages are appended to the file `colored_stderr_debug_log.txt` in the
+current working directory _if_ it exists. Be careful, this file might grow
+very quickly.
*Important:* Warnings are written to `$HOME/colored_stderr_warning_log.txt`
even if it _does not_ exist (only if debug or warning mode is enabled)! If it
warnings are appended at the end.
+KNOWN ISSUES
+------------
+
+- `{fputc,putc,putchar}_unlocked()` are not hooked with glibc when writing to
+ stdout (which might be redirected to stderr). Can't be fixed as the compiler
+ inlines the code into the program without calling any function.
+- Test `test_stdio.sh` fails on FreeBSD because FreeBSD does handle the above
+ correctly (no inlining), but the test is designed for GNU/Linux.
+- 'COLORED_STDERR_IGNORED_BINARIES' requires the `/proc` file system.
+ Suggestions welcome.
+- Output of `strace` is not always colored correctly as the output from
+ `coloredstderr` is traced and displayed as well.
+
+
BUGS
----
ruderich.org/simon / coloredstderr / coloredstderr.git / blobdiff