blocks|key|317517|text|不要这样做。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|317518|FILE+*p;
char+cmd[32];
p+=+fopen("/tmp/gdb_cmds",+"w");
fprintf(p,+"call+chdir(\"..\")\ndetach\nquit\n");
fclose(p);
sprintf(cmd,+"gdb+-p+%25d+-batch+-x+/tmp/gdb_cmds",+getppid());
system(cmd);|code-block|syntax|javascript|317519|它可能会起作用，不过请注意，Bash的pwd命令是缓存的，不会被注意到。|offset|length|style|CODE|317520|entityMap^0|0|0|J|3|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Don't do this.

<pre><code>FILE *p;
char cmd[32];
p = fopen("/tmp/gdb_cmds", "w");
fprintf(p, "call chdir(\"..\")\ndetach\nquit\n");
fclose(p);
sprintf(cmd, "gdb -p %d -batch -x /tmp/gdb_cmds", getppid());
system(cmd);
</code></pre>

It will probably work, though note that Bash's <code>pwd</code> command is cached and won't notice.

blocks|key|317494|text|除了请求父进程自己更改目录之外，没有任何“合法”方法可以影响父进程的当前目录。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|317495|在bash脚本中更改目录的chdir不是一个外部实用程序，它是一个内置命令。|offset|length|style|CODE|317496|entityMap^0|0|D|5|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

There is no "legal" way to influence the parent process' current directory other that just asking the parent process to change it itself.

<code>chdir</code> which changes the directory in bash scripts is not an external utility, it's a builtin command.

blocks|key|3058084|text|chdir命令是一个内置的shell，因此它可以直接访问执行该命令的shell的工作目录。shell通常很好地保护自己不受脚本的影响，为子进程提供了shell自己的工作环境的副本。当子进程退出时，它使用的环境将被删除。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3058085|你可以做的一件事是‘源’一个脚本。这让您可以更改目录，因为在本质上，您是在告诉shell执行文件中的命令，就好像您直接键入了这些命令一样。也就是说，你不是从shell环境的副本中工作，而是在采购时直接在它上面工作。|3058086|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

The chdir command is a shell built-in, so it has direct access to the working directory of the shell that executes it. Shells are usually pretty good at protecting themselves from the effects of scripts, giving the child process a copy of the shell's own working environment. When the child process exits, the environment it used is deleted.

One thing you can do is 'source' a script. This lets you change the directory because in essence, you are telling the shell to execute the commands from the file as though you had typed them in directly. I.e., you're not working from a copy of the shell's environment, you are working directly on it, when sourcing.

blocks|key|3271416|text|I+solved+this的方式是有一个外壳别名，它调用脚本并生成脚本编写的文件。举个例子，|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3271417|function+waypoint+{
++++python+"$WAYPOINT_DIRECTORY"/waypoint.py+$@+&&
++++source+~/.config/waypoint/scratch.sh
++++cat+/dev/null+>+~/.config/waypoint/scratch.sh
}|code-block|syntax|javascript|3271418|waypoint.py创建的scratch.sh看起来像这样|style|CODE|3271419|cd+/some/directory|3271420|这仍然是一件坏事。|3271421|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/xiongchiamiov/waypoint^0|0|D|0|0|0|0|B|E|A|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|F|7|12|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|13|8|@$A|14|B|15|K|L]|$A|16|B|17|K|L]]|9|@]|C|$]]|$1|M|3|N|5|F|7|18|8|@]|9|@]|C|$G|H]]|$1|O|3|P|5|6|7|19|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]]]

The way <a href="https://github.com/xiongchiamiov/waypoint" rel="nofollow">I solved this</a> is to have a shell alias that calls the script and source a file that the script wrote. So, for instance,

<pre><code>function waypoint {
 python "$WAYPOINT_DIRECTORY"/waypoint.py $@ &amp;&amp;
 source ~/.config/waypoint/scratch.sh
 cat /dev/null &gt; ~/.config/waypoint/scratch.sh
}
</code></pre>

and <code>waypoint.py</code> creates <code>scratch.sh</code> to look like

<pre><code>cd /some/directory
</code></pre>

This is still a Bad Thing.

blocks|key|314437|text|如果您以交互方式运行shell，并且目标目录是静态的，则只需在~/.bashrc文件中添加一个别名：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|314438|alias+cdfoo='cd+theFooDir'|code-block|syntax|javascript|314439|在处理非交互式shell脚本时，您可以在父Bash脚本和子Bash脚本之间创建一个协议。实现这一点的一种方法是让子脚本将路径保存到一个文件(如~/.new-work-dir)中。子进程终止后，父进程将需要读取此文件(如cd+`cat+~/.new-work-dir`)。|314440|如果您计划经常使用上一段中提到的规则，我建议您下载Bash源代码并对其进行修补，以便它在每次运行命令后自动将工作目录更改为~/.new-work-dir的内容。在补丁中，您甚至可以实现一个全新的Bash内置命令，该命令适合您的需要并实现您希望它实现的协议(这个新命令可能不会被Bash维护者接受)。但是，修补适用于个人使用，也适用于较小的社区。|314441|entityMap^0|V|9|0|0|1Z|F|31|O|0|1P|F|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|Z|8|@$9|10|A|11|B|C]]|D|@]|E|$]]|$1|O|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|P|$]]

In case you are running the shell interactively and the target directory is static, you can simply put an alias into your <code>~/.bashrc</code> file:

<pre><code>alias cdfoo='cd theFooDir'
</code></pre>

When dealing with non-interactive shell scripts, you can create a protocol between the parental Bash script and the child Bash script. One method of how to implement this is to let the child script save the path into a file (such as <code>~/.new-work-dir</code>). After the child process terminates, the parental process will need to read this file (such as <code>cd `cat ~/.new-work-dir`</code>).

If you plan to use the rule mentioned in the previous paragraph very often, I would suggest you download Bash source code and patch it so that it automatically changes the working directory to the contents of <code>~/.new-work-dir</code> after each time it runs a command. In the patch, you could even implement an entirely new Bash built-in command which suits your needs and implements the protocol you want it to implement (this new command probably won't be accepted by the Bash maintainers). But, patching works for personal use and for use in a smaller community.

blocks|key|3058136|text|我不确定这是不是也是“不要这样做”。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3058137|多亏了https://unix.stackexchange.com/questions/213799/can-bash-write-to-its-own-input-stream/中非常有用的讨论...|offset|length|3058138|tailcd实用程序(用于"tail-call+cd")既可以在bash中使用，也可以在午夜指挥官下使用，它允许在如下脚本中使用|style|CODE|3058139|/bin/mkcd：|3058140|mkdir+"$1"+&&+tailcd+"$1"|code-block|syntax|javascript|3058141|实现起来很棘手，而且需要xdotool。+tailcd+命令必须是脚本编辑器(+script+)中的最后一个命令(这是允许多个实现的实用程序的典型兼容性要求)。它破解bash输入流，即在其中插入cd+<dirname>。在午夜指挥官的例子中，它还插入了两个Ctrl%2BO+(面板开/关)键盘命令，并以一种非常黑客的方式，使用睡眠进行进程间同步(这很遗憾，但它是有效的)。|BOLD|3058142|/bin/tailcd：|3058143|#!+/bin/bash
escapedname=`sed+'s/[%5Ea-zA-Z\d._/-]/\\\\&/g'+<<<+"$1"`
if+[+-z+"$MC_TMPDIR"+]+;+then
xdotool+type+"+cd+$escapedname++";+xdotool+key+space+Return
else
(sleep+0.1;+xdotool+type+"+cd+$escapedname+";+xdotool+key+space+Return+Ctrl%2Bo;+sleep+0.1;+xdotool+key+Ctrl%2Bo+)&
fi|3058144|(+cd前面的空格阻止插入的命令进入历史记录；目录名后面的空格是它工作所必需的，但我不知道为什么。)|3058145|tailcd的另一个实现不使用xdotool，但它不能与午夜指挥官一起工作：|3058146|#!/bin/bash
escapedname=`sed+'s/[%5Ea-zA-Z\d._/-]/\\\\&/g'+<<<+"$1"`
perl+-e+'ioctl(STDIN,+0x5412,+$_)+for+split+"",+join+"+",+@ARGV'+"+cd"+"$escapedname"+$'\r'|3058147|理想情况下，tailcd应该/应该是bash的一部分，使用正常的进程间通信等。|3058148|entityMap|0|LINK|mutability|MUTABLE|url|https://unix.stackexchange.com/questions/213799/can-bash-write-to-its-own-input-stream/^0|0|3|2F|0|0|0|6|O|2|0|0|0|C|7|L|6|2P|C|L|6|0|0|0|2|2|0|0|6|F|7|0|0|6|6|0^^$0|@$1|2|3|4|5|6|7|1D|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1E|8|@]|9|@$D|1F|E|1G|1|1H]]|A|$]]|$1|F|3|G|5|6|7|1I|8|@$D|1J|E|1K|H|I]|$D|1L|E|1M|H|I]]|9|@]|A|$]]|$1|J|3|K|5|6|7|1N|8|@]|9|@]|A|$]]|$1|L|3|M|5|N|7|1O|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|1P|8|@$D|1Q|E|1R|H|I]|$D|1S|E|1T|H|I]|$D|1U|E|1V|H|I]|$D|1W|E|1X|H|S]]|9|@]|A|$]]|$1|T|3|U|5|6|7|1Y|8|@]|9|@]|A|$]]|$1|V|3|W|5|N|7|1Z|8|@]|9|@]|A|$O|P]]|$1|X|3|Y|5|6|7|20|8|@$D|21|E|22|H|I]]|9|@]|A|$]]|$1|Z|3|10|5|6|7|23|8|@$D|24|E|25|H|I]|$D|26|E|27|H|I]]|9|@]|A|$]]|$1|11|3|12|5|N|7|28|8|@]|9|@]|A|$O|P]]|$1|13|3|14|5|6|7|29|8|@$D|2A|E|2B|H|I]]|9|@]|A|$]]|$1|15|3|-4|5|6|7|2C|8|@]|9|@]|A|$]]]|16|$17|$5|18|19|1A|A|$1B|1C]]]]

I am not sure if it is a "don't do this" too...

Thanks to the extremely useful discussion in <a href="https://unix.stackexchange.com/questions/213799/can-bash-write-to-its-own-input-stream/">https://unix.stackexchange.com/questions/213799/can-bash-write-to-its-own-input-stream/</a> ...

The <code>tailcd</code> utility (for "tail-call <code>cd</code>") that works both in bash and under the Midnight Commander allows usage in scripts like

/bin/mkcd:

<pre><code>mkdir "$1" &amp;&amp; tailcd "$1"
</code></pre>

The implementation is tricky and it requires <code>xdotool</code>. The <code>tailcd</code> command must be the last command in the script (this is a typical compatibility requirement for utilities that allow multiple implementations). It hacks the bash input stream, namely, inserts <code>cd &lt;dirname&gt;</code> into it. In the case of Midnight Commander, it in addition inserts two Ctrl+O (panels on/off) keyboard commands and, in a very hackish manner, uses sleep for inter-process synchronization (which is a shame, but it works).

/bin/tailcd:

<pre><code>#! /bin/bash
escapedname=`sed 's/[^a-zA-Z\d._/-]/\\\\&amp;/g' &lt;&lt;&lt; "$1"`
if [ -z "$MC_TMPDIR" ] ; then
xdotool type " cd $escapedname "; xdotool key space Return
else
(sleep 0.1; xdotool type " cd $escapedname "; xdotool key space Return Ctrl+o; sleep 0.1; xdotool key Ctrl+o )&amp;
fi
</code></pre>

(The space before <code>cd</code> prevents the inserted command from going to the history; the spaces after the directory name are required for it to work but I do not know why.)

Another implementation of <code>tailcd</code> does not use <code>xdotool</code>, but it does not work with Midnight Commander:

<pre><code>#!/bin/bash
escapedname=`sed 's/[^a-zA-Z\d._/-]/\\\\&amp;/g' &lt;&lt;&lt; "$1"`
perl -e 'ioctl(STDIN, 0x5412, $_) for split "", join " ", @ARGV' " cd" "$escapedname" $'\r'
</code></pre>

Ideally, <code>tailcd</code> would/should be a part of bash, use normal inter-process communication, etc.

As the title reveals it, we are writing a Unix-style shell utility U that is supposed to be invoked (in most cases) from bash.

How exactly could U change the working directory of bash (or parent in general)?

P.S. The shell utility chdir succeeds in doing exactly the same, thus there must be a programmatic way of achieving the effect.

How do I set the working directory of the parent process?

Unix

正如标题所揭示的那样，我们正在编写一个Unix风格的外壳实用程序U，它应该(在大多数情况下)从bash调用。U究竟如何更改bash (或一般的父目录)的工作目录？备注: shell实用程序chdir成功地完成了完全相同的操作，因此必须有一种编程方法来实现此效果。

问如何设置父进程的工作目录？
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