tests/example_exec.c: Sort environment variables.

[coloredstderr/coloredstderr.git] / README

diff --git a/README b/README
index 6bedd742c33faf44818ec01e06029d20f8cc19ec..5e2209efdd37a5c29813359150938da8f770e31f 100644 (file)
--- a/README
+++ b/README
@@ -6,6 +6,8 @@ coloredstderr is a small library which uses 'LD_PRELOAD' to color stderr.
 
 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')
@@ -31,6 +33,32 @@ DEPENDENCIES
 - dynamic linker/loader which supports 'LD_PRELOAD' (e.g. GNU/Linux'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
 -----
 
@@ -57,8 +85,7 @@ A default setup could look like this:
 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).
@@ -67,6 +94,25 @@ The following additional environment variables are available:
   terminal, e.g. when writing to a file. By default, only writes to a terminal
   are colored.
 
+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" # red
+    COLORED_STDERR_POST="${esc}[0m" # default
+    export COLORED_STDERR_PRE COLORED_STDERR_POST
+
 
 DEBUG
 -----
@@ -74,15 +120,15 @@ DEBUG
 To enable debug mode, configure coloredstderr with '--enable-debug'.
 
 *Important:* Debug mode enables `assert()`s in the code which might abort the
-process if an error condition is detected!
+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'. `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
@@ -90,6 +136,14 @@ doesn't exist it's created. An existing file isn't overwritten, but the
 warnings are appended at the end.
 
 
+KNOWN ISSUES
+------------
+
+- `{fputc,putc,putchar}_unlocked()` are not hooked 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.
+
+
 BUGS
 ----