1 asmlinkage long sys_dup(unsigned int fildes)
2 {
3 int ret = -EBADF;
4 struct file * file = fget(fildes);
5
6 if (file)
7 ret = dupfd(file, 0);
8 return ret;
9 }
10
2 {
3 int ret = -EBADF;
4 struct file * file = fget(fildes);
5
6 if (file)
7 ret = dupfd(file, 0);
8 return ret;
9 }
10
而sys_dup()的主体是dupfd()Q定义在同一个文件中Q：
1 static int dupfd(struct file *file, int start)
2 {
3 struct files_struct * files = current->files;
4 int ret;
5
6 ret = locate_fd(files, file, start);
7 if (ret < 0)
8 goto out_putf;
9 allocate_fd(files, file, ret);
10 return ret;
11
12 out_putf:
13 write_unlock(&files->file_lock);
14 fput(file);
15 return ret;
16 }
17
2 {
3 struct files_struct * files = current->files;
4 int ret;
5
6 ret = locate_fd(files, file, start);
7 if (ret < 0)
8 goto out_putf;
9 allocate_fd(files, file, ret);
10 return ret;
11
12 out_putf:
13 write_unlock(&files->file_lock);
14 fput(file);
15 return ret;
16 }
17
注：dup和dup2的原型如下：
#include <unistd.h>
int dup(int file_descriptor);
int dup2(int file_descriptor1, int file_descriptor2)
dupq回的文件描q符L取最的可用?br />dup2q回的文件描q符或者与file_descriptor2相同Q或者是W一个大于该参数的可用倹{?/font>
而这么一个简单的pȝ调用是如何完成重定向q个艰巨的Q务的呢？我们不妨先看个例子?br /> 当我们在shell下输入如下命令：“echo hello!”，q条命o要求shellq程执行一个可执行文gechoQ参Cؓ“hello!”。当shell接收到命令之后，先找? bin/echoQ然后fork()Z个子q程让他执行bin/echoQƈ参C递给它，而这个进E从shelll承了三个标准文Ӟx准输? QstdinQ，标准输出QstdoutQ和标准出错信息QstderrQ，他们三个的文件号分别????/font>而至于echoq程的工作很单，是参数“hello!”写到标准输出文件中去，通常都是我们的显C器上。但是如果我们将命oҎ“echo hello! > foo”，则在执行时输出将会被重定向到盘文gfoo?font color="#0000FF">Q注Q重定向于文件描q符有关Q?/font>。我们假定在此之前该shellq程只有三个标准文g打开Q文件号分别???Q以上命令行按如下序列执行Q?br /> (1) 打开或创建磁盘文件fooQ如果foo中原来有内容Q则清除原来内容Q其文g号ؓ3?br /> (2) 通过dup()复制文gstdoutQ即文件号1出的filel构指针复制到文件号4处，目的是将stdout的file指针暂时保存一?br /> (3) 关闭stdoutQ即1hӞ但是׃4h件对stdout也同时有个引用，所以stdout文gq未真正关闭Q只是腾?h件号位置?br /> (4) 通过dup()Q复?hӞ即磁盘文件fooQ，׃1h件关闭，其位|空~，?h件被复制?P卌E中原来指向stdout的指针指向了foo?br /> (5) 通过pȝ调用fork()和exec()创徏子进Eƈ执行echoQ子q程在执行echo前夕关闭3号和4hӞ只留???三个文gQ请注意Q这 时的1h件已l不是stdout而是盘文gfoo了。当echo惛_stdout文g写入“hello!”时自然写入到了foo中?br /> (6) 回到shell后，关闭指向foo?号与3h件文Ӟ再用dup()和close()?h复至stdoutQ这样shell恢复了0??三个标准输入/输出文g?br />
由此可见Q?font color="#FF0000">当echoE序Q或其他Q在q行的时候ƈ不知道stdoutQ对于stdin和stderr同样Q指向什么，q程与实际输出文件或讑֤的结合是在运行时由其父进E“包办”的。这样就化了子进E的E序设计Q因为在设计时只要跟三个逻辑上存在的文g打交道就可以?/font>。可能有Z觉得q很像面向对象中 的多态和重蝲Q没有什么新奇之处，但是如果你活?0甚至40q前Q可能你会改变你的看法。?
]]>
W一?定ath9k_htc驱动支持你的|卡型号
http://linuxwireless.org/en/users/Drivers/ath9k_htc/devices 列出了支持的型号列表Q你可以通过lsusb查看自己的网卡型h否在列表当中?br />
W二?安装firmwire
?a >q里下蝲htc_9271.fwQ拷贝到/lib/firmwire?br />
W三?安装compact wireless
安装compact wireless有打包好的deb包，?a >q里下蝲GUI Program to install ath9k_htcQ安装完后直接运行，{待安装完成重启机器可以了?br />爱折腄也可以到http://wireless.kernel.org/download/
最新的compact wireless驱动Q然后编译安装：
sudo make
sudo make install
sudo make unload
sudo make load ath9k_htc
重启机器卛_?br />
http://forum.ubuntu.com.cn/viewtopic.php?f=116&t=326568&p=2388841
http://blog.chinaunix.net/space.php?uid=20620288&do=blog&id=2691282
]]>
| Code | Meaning |
|---|---|
| D | Uninterruptible sleep (usually IO) |
| R | Running or runnable (on run queue) |
| S | Interruptible sleep (waiting for an event to complete) |
| T | Stopped, either by a job control signal or because it is being traced. |
| W | paging (not valid since the 2.6.xx kernel) |
| X | dead (should never be seen) |
| Z | Defunct (“zombie? process, terminated but not reaped by its parent. |
For BSD formats and when the stat keyword is used, additional characters may be displayed:
| Code | Meaning |
|---|---|
| < | high-priority (not nice to other users) |
| N | low-priority (nice to other users) |
| L | has pages locked into memory (for real-time and custom IO) |
| s | is a session leader |
| l | is multi-threaded (using CLONE_THREAD, like NPTL pthreads do) |
| + | is in the foreground process group |
Process in D state
If there are a lot of processes in D state in your system, then something is wrong with it.
What is D state and a process state in general? A process in Linux can be in several states: running,
sleeping, etc. Running process runs on a CPU just now, sleeping process waits for its turn on CPU
or for some other event. Using ps command you can obtain information about state of each process in the system: STAT column shows that:
# ps a PID TTY STAT TIME COMMAND 4975 tty1 Ss+ 0:00 /sbin/mingetty tty1 4976 tty2 Ss+ 0:00 /sbin/mingetty tty2 6202 pts/0 Ss+ 0:01 -bash 10312 pts/1 Ss 0:00 -bash 639 pts/1 R+ 0:00 ps a
First big S stands for Sleeping, R stands for running ("+" means that the process is foreground and small "s" means that the process is session leader, but it is not relevant for this article).
D state occurs then the process is in uninterruptible
sleep. This state is bad, because you can't do anything with the process
in D state. Fortunately, process normally remains in such state not for
so long. But if you have a heap of D state processes then some logic in
system is disrupt. If that is happening, the very important thing is to
determine where this unlucky sleep occurs. It is easy to do with ps
command with l option. WCHAN column shows the name of the kernel function where the process is sleeping:
# ps axl | grep D F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND vass 13478 7.2 0.0 1732 624 pts/1 D+ 17:36 0:00 find ./
http://wiki.preshweb.co.uk/doku.php?id=linux:psflags
http://wiki.openvz.org/Processes_in_D_state
]]>
interactive-program <<delimiter
command #1
command #2
...
delimiter
默认情况下，变量会被替换Q?br /> $ cat << EOF
> Working dir $PWD
> EOF
Working dir /home/user
如果delimiter用双引号引v来，则不会有变量替换Q?br /> $ cat << "EOF"
> Working dir $PWD
> EOF
Working dir $PWD
重定?W号 << 可以使用 <<- Q在q种情况下，heredoc 文本中的前导 tab 字符会被删除Q但是空g会被删除Q?br />
注意Q?br />l束标记前一定不能有MI格或者tabQ否则执行失败！
heredoc 另外一个比较有用的是显C消息块Q如Usage信息Q?br />
cat <<End-of-message ------------------------------------- This is line 1 of the message. This is line 2 of the message. This is line 3 of the message. This is line 4 of the message. This is the last line of the message. ------------------------------------- End-of-message
参考：
http://tldp.org/LDP/abs/html/here-docs.html
http://febird.iteye.com/blog/588509
http://en.wikipedia.org/wiki/Here_document
]]>
1 cat data.dat | while read line
2 do
3 echo "File: ${line}"
4 done
5
6 while read line
7 do
8 echo "File: ${line}"
9 done < data.dat
2 do
3 echo "File: ${line}"
4 done
5
6 while read line
7 do
8 echo "File: ${line}"
9 done < data.dat
如果输入文本每行中没有空|也可以采用以下两U进行处理，代码如下Q?br />
1 for line in $(cat data.dat)
2 do
3 echo "File: ${line}"
4 done
5
6 for line in `cat data.dat`
7 do
8 echo "File: ${line}"
9 done
2 do
3 echo "File: ${line}"
4 done
5
6 for line in `cat data.dat`
7 do
8 echo "File: ${line}"
9 done
如输入文本行中包括空|那么会以I格来区分开多个元素Q结果就不是按行d了?br />
当然如果只是单纯的数据或文本的按行读取和昄的话Q用awk命o会更为方ѝ?/span>
当然如果只是单纯的数据或文本的按行读取和昄的话Q用awk命o会更为方ѝ?/span>
http://witmax.cn/shell-read-line.html
]]>
pȝ声卡信息为：
$ lspci -v|grep -i audio
00:1b.0 Audio device: Intel Corporation 5 Series/3400 Series Chipset High Definition Audio (rev 05)
$ cat /proc/asound/card0/codec* | grep Codec
Codec: IDT 92HD81B1X5
Codec: Intel G45 DEVIB
google一通，有帖子说要修?/etc/modprobe.d/alsa-base.conf
加上Q?br /> alias snd-card-0 snd-hda-intel
alias sound-slot-0 snd-hda-intel
options snd-hda-intel model=hp(q里需要找到和你机器匹配的mode)
options snd-hda-intel enable_msi=1
重启后不用?br />
查看机器上的alsa驱动的版本：
cat /proc/asound/version
昄版本?.0.21Q怀疑是不是版本太低了，于是试更新alsa驱动版本Q搜索到q篇帖子Q?br /> http://monespaceperso.org/blog-en/2010/05/02/upgrade-alsa-1-0-23-on-ubuntu-lucid-lynx-10-04/
升alsa驱动?.0.24版本后，故障排除?br /> $ cat /proc/asound/version
Advanced Linux Sound Architecture Driver Version 1.0.24.
Compiled on May 15 2011 for kernel 2.6.32-31-generic (SMP).
只是不知道ؓ什么设备信息变成了Q?br /> $ cat /proc/asound/card0/codec* | grep Codec
Codec: IDT 92HD81B1X5
Codec: Intel IbexPeak HDMI
]]>
* 打包Q?br /> tar cf allfile.tar *.jpg
* 解包到指定的目录Q?br /> tar xf allfile.tar -C ~/Pictures
* 列出tar包中的所有文Ӟ
tar tf allfile.tar
* 往已有的tar包中增加新文Ӟ
tar rf allfile.tar *.png
使用tar命o处理其它压羃法
* gzip(.tar.gz或?tgz)
tar zcf allfile.tar.gz *.jpg
tar zxf allfile.tar.gz -C ~/Pictures
* bzip2(.tar.bz2或?bz2)
tar jcf allfile.tar.bz2 *.jpg
tar jxf allfile.tar.bz2 -C ~/Pictures
归档里面的所有文件均是相对引用，归档解压~（释放Q在了当前目录。归档文件L释放到当前目录，为的是防止破坏文件系l中重名的文件?br /> 如果惌盖的话，在归档和解压时请使用-P参数Q?br /> tar zcvf mysql.tar.gz -P /var/lib/mysql
tar -Pzxvf mysql.tar.gz(q会覆盖本地?var/lib/mysql目录)
Tar炸弹
d者利用绝对\径，或者“tar -cf bomb.tar *”的方式创徏的tar文gQ然后诱骗受完在根目录下解压Q或者用绝对\径解压。可能受害pȝ上已有的文g被覆盖掉Q或者导致当前工作目录凌׃ 堪，q就是所谓的“tar炸弹”。因此，要养成良好的解压习惯Q?/p>
- 解压前用“t”查看tar的文件内宏V?/li>
- 拒绝使用l对路径?/li>
- 新徏一个时子目录Q然后在q个子目录里解压?/li>
]]>
~辑Q?br /> ~/.mozilla/firefox/XXXXXX.default/chrome/userChrome.jsQ?br />
(function() {
var win_ctrl = document.getElementById("window-controls");
win_ctrl.setAttribute("fullscreencontrol", "false");
win_ctrl.setAttribute("hidden", "false");
var mainWindow = document.getElementById("main-window");
mainWindow.setAttribute("hidechrome", "true");
})();
That's all.
]]>
查找触摸板的idQ?br /> ?Virtual core pointer id=2 [master pointer (3)]
? ?Virtual core XTEST pointer id=4 [slave pointer (2)]
? ?USB Optical Mouse id=10 [slave pointer (2)]
? ?PS/2 Synaptics TouchPad id=13 [slave pointer (2)]
? ?Macintosh mouse button emulation id=14 [slave pointer (2)]
?Virtual core keyboard id=3 [master keyboard (2)]
?Virtual core XTEST keyboard id=5 [slave keyboard (3)]
?Power Button id=6 [slave keyboard (3)]
?Video Bus id=7 [slave keyboard (3)]
?Video Bus id=8 [slave keyboard (3)]
?Power Button id=9 [slave keyboard (3)]
?HP Webcam-101 id=11 [slave keyboard (3)]
?AT Translated Set 2 keyboard id=12 [slave keyboard (3)]
触摸板的ID?3Q?br /> 用Q?br /> 代码:
xinput set-prop 13 "Device Enabled" 0
启用Q?br /> 代码:
xinput set-prop 13 "Device Enabled" 1
]]>
1.~辑/etc/apt/sources.list文gQ将安装源更改ؓUbuntu 9.04的安装源为：
deb http://archive.Ubuntu.com/ubuntu/ jaunty main restricted universe multiverse
deb http://archive.Ubuntu.com/ubuntu/ jaunty-security main restricted universe multiverse
deb http://archive.Ubuntu.com/ubuntu/ jaunty-updates main restricted universe multiverse
deb http://archive.Ubuntu.com/ubuntu/ jaunty-proposed main restricted universe multiverse
deb http://archive.Ubuntu.com/ubuntu/ jaunty-backports main restricted universe multiverse
deb-src http://archive.Ubuntu.com/ubuntu/ jaunty main restricted universe multiverse
deb-src http://archive.Ubuntu.com/ubuntu/ jaunty-security main restricted universe multiverse
deb-src http://archive.Ubuntu.com/ubuntu/ jaunty-updates main restricted universe multiverse
deb-src http://archive.Ubuntu.com/ubuntu/ jaunty-proposed main restricted universe multiverse
2. sudo apt-get install sun-java5-jdk
]]>
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