blocks|key|1745149|text|摘自popen手册：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1745150|#include+<stdio.h>

FILE+*popen(const+char+*command,+const+char+*type);

int+pclose(FILE+*stream);|code-block|syntax|javascript|1745151|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

From the popen manual:

<pre><code>#include &lt;stdio.h&gt;

FILE *popen(const char *command, const char *type);

int pclose(FILE *stream);
</code></pre>

blocks|key|1745218|text|尝试popen()函数。它执行一个命令，如system()，但将输出定向到一个新文件中。返回指向该流的指针。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1745219|++FILE+*lsofFile_p+=+popen("lsof",+"r");

++if+(!lsofFile_p)
++{
++++return+-1;
++}

++char+buffer[1024];
++char+*line_p+=+fgets(buffer,+sizeof(buffer),+lsofFile_p);
++pclose(lsofFile_p);|code-block|syntax|javascript|1745220|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try the popen() function. It executes a command, like system(), but directs the output into a new file. A pointer to the stream is returned.

<pre><code> FILE *lsofFile_p = popen("lsof", "r");

 if (!lsofFile_p)
 {
 return -1;
 }

 char buffer[1024];
 char *line_p = fgets(buffer, sizeof(buffer), lsofFile_p);
 pclose(lsofFile_p);
</code></pre>

blocks|key|1745062|text|编辑:将问题误读为希望将输出传递给另一个程序，而不是另一个函数。popen()几乎肯定是您想要的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1745063|系统为您提供对shell的完全访问权限。如果你想继续使用它，你可以通过系统将它的输出重定向到一个临时文件(“ls>+tempfile.txt")，但是选择一个安全的临时文件是一件痛苦的事情。或者，您甚至可以通过另一个程序重定向它:+system("ls+%7C+otherprogram")；|1745064|有些人可能会推荐popen()命令。如果您可以自己处理输出，这就是您想要的结果：|1745065|FILE+*output+=+popen("ls",+"r");|code-block|syntax|javascript|1745066|这将为您提供一个文件指针，您可以从中读取命令的输出。|1745067|您还可以使用管道()调用来创建连接，同时使用fork()来创建新进程，使用dup2()来更改它们的标准输入和输出，使用exec()来运行新程序，并在主程序中使用wait()来等待它们。这只是在设置管道，就像shell一样。有关详细信息和示例，请参阅管道()手册页。|1745068|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|S|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|T|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

EDIT: misread question as wanting to pass output to another program, not another function. popen() is almost certainly what you want.

System gives you full access to the shell. If you want to continue using it, you can
 redirect it's output to a temporary file, by system("ls > tempfile.txt"), but choosing a secure temporary file is a pain. Or, you can even redirect it through another program: system("ls | otherprogram");

Some may recommend the popen() command. This is what you want if you can process the output yourself:

<pre><code>FILE *output = popen("ls", "r");
</code></pre>

which will give you a FILE pointer you can read from with the command's output on it.

You can also use the pipe() call to create a connection in combination with fork() to create new processes, dup2() to change the standard input and output of them, exec() to run the new programs, and wait() in the main program to wait for them. This is just setting up the pipeline much like the shell would. See the pipe() man page for details and an example.

blocks|key|1745336|text|函数popen()等不会重定向stderr等；我为此编写了popen3()。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1745337|下面是我的popen3()的简化版本：|1745338|int+popen3(int+fd[3],const+char+**const+cmd)+{
++++++++int+i,+e;
++++++++int+p[3][2];
++++++++pid_t+pid;
++++++++//+set+all+the+FDs+to+invalid
++++++++for(i=0;+i<3;+i%2B%2B)
++++++++++++++++p[i][0]+=+p[i][1]+=+-1;
++++++++//+create+the+pipes
++++++++for(int+i=0;+i<3;+i%2B%2B)
++++++++++++++++if(pipe(p[i]))
++++++++++++++++++++++++goto+error;
++++++++//+and+fork
++++++++pid+=+fork();
++++++++if(-1+==+pid)
++++++++++++++++goto+error;
++++++++//+in+the+parent?
++++++++if(pid)+{
++++++++++++++++//+parent
++++++++++++++++fd[STDIN_FILENO]+=+p[STDIN_FILENO][1];
++++++++++++++++close(p[STDIN_FILENO][0]);
++++++++++++++++fd[STDOUT_FILENO]+=+p[STDOUT_FILENO][0];
++++++++++++++++close(p[STDOUT_FILENO][1]);
++++++++++++++++fd[STDERR_FILENO]+=+p[STDERR_FILENO][0];
++++++++++++++++close(p[STDERR_FILENO][1]);
++++++++++++++++//+success
++++++++++++++++return+0;
++++++++}+else+{
++++++++++++++++//+child
++++++++++++++++dup2(p[STDIN_FILENO][0],STDIN_FILENO);
++++++++++++++++close(p[STDIN_FILENO][1]);
++++++++++++++++dup2(p[STDOUT_FILENO][1],STDOUT_FILENO);
++++++++++++++++close(p[STDOUT_FILENO][0]);
++++++++++++++++dup2(p[STDERR_FILENO][1],STDERR_FILENO);
++++++++++++++++close(p[STDERR_FILENO][0]);
++++++++++++++++//+here+we+try+and+run+it
++++++++++++++++execv(*cmd,const_cast<char*const*>(cmd));
++++++++++++++++//+if+we+are+there,+then+we+failed+to+launch+our+program
++++++++++++++++perror("Could+not+launch");
++++++++++++++++fprintf(stderr,"+\"%25s\"\n",*cmd);
++++++++++++++++_exit(EXIT_FAILURE);
++++++++}

++++++++//+preserve+original+error
++++++++e+=+errno;
++++++++for(i=0;+i<3;+i%2B%2B)+{
++++++++++++++++close(p[i][0]);
++++++++++++++++close(p[i][1]);
++++++++}
++++++++errno+=+e;
++++++++return+-1;
}|code-block|syntax|javascript|1745339|entityMap|0|LINK|mutability|MUTABLE|url|http://sites.google.com/site/williamedwardscoder/popen3^0|2|7|T|8|T|8|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|F|3|G|5|6|7|12|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|13|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

The functions <code>popen()</code> and such don't redirect stderr and such; I wrote <a href="http://sites.google.com/site/williamedwardscoder/popen3" rel="nofollow noreferrer"><code>popen3()</code></a> for that purpose.

Here's a bowdlerised version of my popen3():

<pre><code>int popen3(int fd[3],const char **const cmd) {
 int i, e;
 int p[3][2];
 pid_t pid;
 // set all the FDs to invalid
 for(i=0; i&lt;3; i++)
 p[i][0] = p[i][1] = -1;
 // create the pipes
 for(int i=0; i&lt;3; i++)
 if(pipe(p[i]))
 goto error;
 // and fork
 pid = fork();
 if(-1 == pid)
 goto error;
 // in the parent?
 if(pid) {
 // parent
 fd[STDIN_FILENO] = p[STDIN_FILENO][1];
 close(p[STDIN_FILENO][0]);
 fd[STDOUT_FILENO] = p[STDOUT_FILENO][0];
 close(p[STDOUT_FILENO][1]);
 fd[STDERR_FILENO] = p[STDERR_FILENO][0];
 close(p[STDERR_FILENO][1]);
 // success
 return 0;
 } else {
 // child
 dup2(p[STDIN_FILENO][0],STDIN_FILENO);
 close(p[STDIN_FILENO][1]);
 dup2(p[STDOUT_FILENO][1],STDOUT_FILENO);
 close(p[STDOUT_FILENO][0]);
 dup2(p[STDERR_FILENO][1],STDERR_FILENO);
 close(p[STDERR_FILENO][0]);
 // here we try and run it
 execv(*cmd,const_cast&lt;char*const*&gt;(cmd));
 // if we are there, then we failed to launch our program
 perror("Could not launch");
 fprintf(stderr," \"%s\"\n",*cmd);
 _exit(EXIT_FAILURE);
 }

 // preserve original error
 e = errno;
 for(i=0; i&lt;3; i++) {
 close(p[i][0]);
 close(p[i][1]);
 }
 errno = e;
 return -1;
}
</code></pre>

blocks|key|1745129|text|在Windows中，不使用system()，而是使用CreateProcess，将输出重定向到管道并连接到管道。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1745130|我猜这在某种POSIX方式下也是可能的？|1745131|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|$]]

In Windows, instead of using system(), use CreateProcess, redirect the output to a pipe and connect to the pipe.

I'm guessing this is also possible in some POSIX way?

blocks|key|1745268|text|函数popen()和pclose()可能就是您要找的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1745269|看看glibc+manual中的一个例子。|1745270|entityMap|0|LINK|mutability|MUTABLE|url|http://www.gnu.org/software/libc/manual/html_mono/libc.html#Pipe-to-a-Subprocess^0|2|7|A|8|0|2|C|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]|$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|U|8|@]|D|@$9|V|A|W|1|X]]|E|$]]|$1|H|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]]]

The functions <code>popen()</code> and <code>pclose()</code> could be what you're looking for.

Take a look at the <a href="http://www.gnu.org/software/libc/manual/html_mono/libc.html#Pipe-to-a-Subprocess" rel="nofollow noreferrer">glibc manual</a> for an example.

blocks|key|1530063|text|我不能完全确定这在标准C中是否可行，因为两个不同的进程通常不共享内存空间。我能想到的最简单的方法是让第二个程序将其输出重定向到一个文本文件(programname+>+textfile.txt)，然后读回该文本文件进行处理。然而，这可能不是最好的方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1530064|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I'm not entirely certain that its possible in standard C, as two different processes don't typically share memory space. The simplest way I can think of to do it would be to have the second program redirect its output to a text file (programname > textfile.txt) and then read that text file back in for processing. However, that may not be the best way.

I'm trying to start an external application through <code>system()</code> - for example, <code>system("ls")</code>. I would like to capture its output as it happens so I can send it to another function for further processing. What's the best way to do that in C/C++?

Capturing stdout from a system() command optimally

Windows

我正在尝试通过system()启动一个外部应用程序-例如，system("ls")。我想在它发生时捕获它的输出，这样我就可以将它发送到另一个函数进行进一步处理。在C/C++中做到这一点的最好方法是什么？

问以最佳方式从system()命令捕获stdout
EN

回答 7

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问以最佳方式从system()命令捕获stdoutEN

回答 7

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问以最佳方式从system()命令捕获stdout
EN