安装了Linux后当然希望能进入XWindow，象在Windows一样方便地工作，于是大家都可能用过startx命令，也可能是直接在XWindow登录界面进入XWindow。
这两种方式的XWindow启动过程有没有区别呢?如果你没有做过个性化设置可能体会不到，但如果你设置过中文输入法，不管是用SCIM还是fcitx，可能都有过设置输入法为随XWindow启动的经验。
朋友们开始修改各种启动脚本，经常可能会修改到的方法有：
1、修改/etc/X11/xinit/xinitrc
2、修改/etc/X11/Xsession
3、在/etc/X11/Xsession.d目录下增加一个自定义的脚本
4、修改$HOME/.xsession
5、修改$HOME/.xinitrc
6、修改/etc/X11/xdm/Xsession
……
总之，看起来是八仙过海各有各的神通了。这些方法有没有不同?为什么有时候明明设置好了，startx起来可以用了，但重启在XWindow管理界面登录后却不能用了?为什么有时从XWindow管理界面登录后可用，但startx后却用不了?
下面我们一起来分析一下吧。
#!/bin/sh
#
# /etc/X11/Xsession
#
# global Xsession file — used by display managers and xinit (startx)
# $Id: Xsession 2186 2005-02-11 07:11:05Z branden $
set -e
PROGNAME=Xsession
message () {
# pretty-print messages of arbitrary length; use xmessage if it
# is available and $DISPLAY is set
MESSAGE=”$PROGNAME: $*”
echo “$MESSAGE” | fold -s -w ${COLUMNS:-80} >&2
if [ -n “$DISPLAY” ] && which xmessage > /dev/null 2>&1; then
echo “$MESSAGE” | fold -s -w ${COLUMNS:-80} | xmessage -center -file –
fi
}
message_nonl () {
# pretty-print messages of arbitrary length (no trailing newline); use
# xmessage if it is available and $DISPLAY is set
MESSAGE=”$PROGNAME: $*”
echo -n “$MESSAGE” | fold -s -w ${COLUMNS:-80} >&2;
if [ -n “$DISPLAY” ] && which xmessage > /dev/null 2>&1; then
echo -n “$MESSAGE” | fold -s -w ${COLUMNS:-80} | xmessage -center -file –
fi
}
errormsg () {
# exit script with error
message “$*”
exit 1
}
internal_errormsg () {
# exit script with error; essentially a “THIS SHOULD NEVER HAPPEN” message
# One big call to message() for the sake of xmessage; if we had two then
# the user would have dismissed the error we want reported before seeing the
# request to report it.
errormsg “$*”
“Please report the installed version of the “xfree86-common””
“package and the complete text of this error message to”
“.”
}
# initialize variables for use by all session scripts
OPTIONFILE=/etc/X11/Xsession.options
SYSRESOURCES=/etc/X11/Xresources
USRRESOURCES=$HOME/.Xresources
SYSSESSIONDIR=/etc/X11/Xsession.d
USERXSESSION=$HOME/.xsession
ALTUSERXSESSION=$HOME/.Xsession
ERRFILE=$HOME/.xsession-errors
# attempt to create an error file; abort if we cannot
if touch “$ERRFILE” 2> /dev/null && [ -w “$ERRFILE” ] &&
[ ! -L “$ERRFILE” ]; then
chmod 600 “$ERRFILE”
elif ERRFILE=$(tempfile 2> /dev/null); then
if ! ln -sf “$ERRFILE” “${TMPDIR:=/tmp}/xsession-$USER”; then
message “warning: unable to symlink “$TMPDIR/xsession-$USER” to”
“”$ERRFILE”; look for session log/errors in”
“”$TMPDIR/xsession-$USER”.”
fi
else
errormsg “unable to create X session log/error file; aborting.”
fi
exec >>”$ERRFILE” 2>&1
echo “$PROGNAME: X session started for $LOGNAME at $(date)”
# sanity check; is our session script directory present?
if [ ! -d “$SYSSESSIONDIR” ]; then
errormsg “no “$SYSSESSIONDIR” directory found; aborting.”
fi
# Attempt to create a file of non-zero length in /tmp; a full filesystem can
# cause mysterious X session failures. We do not use touch, :, or test -w
# because they won’t actually create a file with contents. We also let standard
# error from tempfile and echo go to the error file to aid the user in
# determining what went wrong.
WRITE_TEST=$(tempfile)
if ! echo “*” >>”$WRITE_TEST”; then
message “warning: unable to write to ${WRITE_TEST%/*}; X session may exit”
“with an error”
fi
rm -f “$WRITE_TEST”
# Use run-parts to source every file in the session directory; we source
# instead of executing so that the variables and functions defined above
# are available to the scripts, and so that they can pass variables to each
# other.
SESSIONFILES=$(run-parts –list $SYSSESSIONDIR)
if [ -n “$SESSIONFILES” ]; then
for SESSIONFILE in $SESSIONFILES; do
. $SESSIONFILE
done
fi
exit 0
此文件的第五行“# global Xsession file — used by display managers and xinit (startx)”已经说明/etc/X11/Xsession脚本是大家公用的，无论你是用XWindow管理器(比如kdm、gdm、xdm)进入还 是通过命令行输入startx(即xinit方式)进入XWindow，都会调用此脚本程序。再看看这个脚本程序做了些什么吧。这一行 “SYSSESSIONDIR=/etc/X11/Xsession.d”定义了一个变量指向了目录/etc/X11/Xsession.d，后面又出现 一段代码：
SESSIONFILES=$(run-parts –list $SYSSESSIONDIR)
if [ -n “$SESSIONFILES” ]; then
for SESSIONFILE in $SESSIONFILES; do
. $SESSIONFILE
done
fi
显然这里是搜索了目录/etc/X11/Xsession.d里面所有的脚本并一一执行完毕。
同时请注意有这么两行：
USERXSESSION=$HOME/.xsession
ALTUSERXSESSION=$HOME/.Xsession
在这里并没有看到使用这两个变量，那么在这个脚本里定义来做什么?下面再看一下脚本/etc/X11/Xsession.d/50xfree86-common_determine-startup里的内容，原文如下：
# $Id: 50xfree86-common_determine-startup 1437 2004-05-23 03:18:32Z branden $
# This file is sourced by Xsession(5), not executed.
# If no X session startup program was passed to the Xsession script as an
# argument (e.g., by the display manager), or if that program was not
# executable, fall back to looking for a user’s custom X session script, if
# allowed by the options file.
if [ -z “$STARTUP” ]; then
if grep -qs ^allow-user-xsession “$OPTIONFILE”; then
for STARTUPFILE in “$USERXSESSION” “$ALTUSERXSESSION”; do
if [ -e “$STARTUPFILE” ]; then
if [ -x “$STARTUPFILE” ]; then
STARTUP=”$STARTUPFILE”
else
STARTUP=”sh $STARTUPFILE”
fi
break
fi
done
fi
fi
# If there is still nothing to use for a startup program, try the system
# default session manager, window manager, and terminal emulator.
if [ -z “$STARTUP” ]; then
if [ -x /usr/bin/x-session-manager ]; then
STARTUP=x-session-manager
elif [ -x /usr/bin/x-window-manager ]; then
STARTUP=x-window-manager
elif [ -x /usr/bin/x-terminal-emulator ]; then
STARTUP=x-terminal-emulator
fi
fi
# If we still have not found a startup program, give up.
if [ -z “$STARTUP” ]; then
ERRMSG=”unable to start X session —”
if grep -qs ^allow-user-xsession “$OPTIONFILE”; then
ERRMSG=”$ERRMSG no “$USERXSESSION” file, no “$ALTUSERXSESSION” file,”
fi
errormsg “$ERRMSG no session managers, no window managers, and no terminal”
“emulators found; aborting.”
fi
# vim:set ai et sts=2 sw=2 tw=80:
这一行“# This file is sourced by Xsession(5), not executed.”证明脚本是被之前的
/etc/X11/Xsession调用的，而后面这一段：
for STARTUPFILE in “$USERXSESSION” “$ALTUSERXSESSION”; do
if [ -e “$STARTUPFILE” ]; then
if [ -x “$STARTUPFILE” ]; then
STARTUP=”$STARTUPFILE”
else
STARTUP=”sh $STARTUPFILE”
fi
break
fi
done
更证明了这一点。在这里脚本搜索用户目录$HOME下的.xsession或.Xsession脚本来执行。
(在/etc/X11/Xsession.d目录下还有一些脚本，这里就不再分析了，各位有兴趣可以自己看看)
另外来看看/etc/X11/xinit/xinitrc这个脚本，其原文内容如下：
##!/bin/sh
## $Xorg: xinitrc.cpp,v 1.3 2000/08/17 19:54:30 cpqbld Exp $
#
## /etc/X11/xinit/xinitrc
##
## global xinitrc file, used by all X sessions started by xinit (startx)
#
## invoke global X session script
. /etc/X11/Xsession
注意这一句“## global xinitrc file, used by all X sessions started by xinit (startx)”，这说明这个脚本只被xinit调用(即用户输入startx时)。而其执行的最后还是执行了/etc/X11/Xsession脚 本。而用户如果用其它XWindow管理界面登录系统时这个脚本里的内容是不会被执行的。最后再来看看/etc/X11/xdm/Xsession这个脚 本吧，其原文内容如下：
#!/bin/sh
#
# $Xorg: Xsession,v 1.4 2000/08/17 19:54:17 cpqbld Exp $
#
#
#
#
# $XFree86: xc/programs/xdm/config/Xsession,v 1.3 2001/01/17 23:45:24 dawes Exp $
# invoke global X session script
. /etc/X11/Xsession
从内容来看，也是最终执行了/etc/X11/Xsession。
再看看/etc/X11里面的目录结构：
X Xsession.d cursors gdm rstart xinit
XF86Config-4 Xsession.options default-display-manager lbxproxy sysconfig xkb
Xresources Xwrapper.config fonts proxymngr twm xserver
Xsession app-defaults fs rgb.txt xdm xsm
显然，这里把xinit和xdm、twm及gdm是分开的，在xinit里执行的脚本是不会被xdm里的脚本调用的。从上面对代码的分析，大家 可以看到：其实XWindow执行的关键脚本是/etc/X11/Xsession，这个脚本会去 /etc/X11/Xsession.d目录里搜索脚本执行，也会去$HOME/下搜索脚本运行，而其它目录xinit、xdm等里面的脚本都会去调用 /etc/X11/Xsession这个脚本。
所以，如果你想把中文输入法fcitx、SCIM等设置成随Xwindow启动，比如要加入如下脚本：
export LC_CTYPE=zh_CN.GBK
export XMODIFIERS=”@im=fcitx”
export XIM=fcitx
export XIM_PROGRAM=fcitx
fcitx
那么可以用如下几种方法：
1、加到/etc/X11/Xsession。这种方法对所有启动方法都管理。
2、在/etc/X11/Xsession.d目录里自己写一个脚本，这种方法也对所有启动方法都管理。
3、在$HOME目录下生成.xsession或.Xsession脚本，这种方法也对当前登录用户有效。
4、加到/etc/X11/xinit/xinitrc脚本里。这个方法只对xinit方式(即命令行输入startx)管用。
5、加到/etc/X11/xdm/xsession脚本里，只对用xdm管理界面登录的方式管用。
from http://www.soft6.com/html/tech/17/173854.shtml
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