在管道中获取命令输出，C在Linux中获取

I need to run a Linux CLI command and get its stdout output from C.

我需要运行Linux CLI命令并从C获取其stdout输出。

I can use pipe() to create a pipe, then fork/exec, redirecting child's stdout descriptor into the pipe before calling exec(), and reading from the pipe in parent. Plus I'll need to wait on the child.

我可以使用pipe()创建一个管道,然后使用fork / exec,在调用exec()之前将child的stdout描述符重定向到管道,并从父管道中读取。另外,我需要等孩子。

Is there a simple call to do fork + redirect + exec + wait, like system() does fork + exec + wait, only system() doesn't do the redirect.

是否有一个简单的调用fork + redirect + exec + wait,就像system()执行fork + exec + wait一样,只有system()不执行重定向。

There's popen(), which does fork + redirect + exec, but doesn't do wait, so I can't get exit status.

有popen(),它执行fork + redirect + exec,但是没有等待,所以我无法获得退出状态。

4 个解决方案

#1

Is this it?

是这个吗?

NAME
       popen, pclose - process I/O

SYNOPSIS
       #include <stdio.h>  

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

       int pclose(FILE *stream);

DESCRIPTION
       The  popen()  function opens a process by creating a pipe, forking, 
and invoking the shell.  Since a pipe is by definition unidirectional, the 
type argument may specify only reading or writing, not both; the resulting 
stream is correspondingly read-only or write-only.

       The command argument is a pointer to a null-terminated string 
containing a shell command line.  This command is passed to /bin/sh 
using the -c flag; interpretation, if any, is performed by the shell.  
The type argument is a pointer to a null-terminated string which must be 
either ‘r’ for reading or ‘w’ for writing.

       The  return  value  from popen() is a normal standard I/O stream in 
all respects save that it must be closed with pclose() rather than fclose().  
Writing to such a stream writes to the standard input of the command; the 
command’s standard output is the same as that of the process that called 
popen(), unless this is altered by the command itself.  Conversely, reading 
from a ‘‘popened’’ stream reads the command’s standard output, and the 
command’s standard input is the same as that of the process that called 
popen().

       Note that output popen() streams are fully buffered by default.

       The pclose() function waits for the associated process to terminate 
and returns the exit status of the command as returned by wait4().

#2

GLib has a nice function for this -- g_spawn_sync(): http://library.gnome.org/devel/glib/stable/glib-Spawning-Processes.html#g-spawn-sync

GLib有一个很好的功能 - g_spawn_sync():http://library.gnome.org/devel/glib/stable/glib-Spawning-Processes.html#g-spawn-sync

For example, to run a command and get its exit status and output:

例如,要运行命令并获取其退出状态并输出:

const char *argv[] = { "your_command", NULL };
char *output = NULL; // will contain command output
GError *error = NULL;
int exit_status = 0;
if (!g_spawn_sync(NULL, argv, NULL, 0, NULL, NULL, 
                  &output, NULL, &exit_status, &error))
{
  // handle error here
}

#3

Use popen() and pclose().

使用popen()和pclose()。

popen() does not actually wait, of course, but reads on the pipe will block until there is data available.

当然,popen()实际上并没有等待,但管道上的读取将会阻塞,直到有可用的数据。

pclose() waits, but calling it prematurely could cut off some output from the forked process. You'll want to determine from the stream when the child is done...

pclose()等待,但过早地调用它可能会切断forked进程的一些输出。当孩子完成时,你会想要从流中确定...

Possibly already discussed at How can I run an external program from C and parse its output?

可能已经讨论过如何从C运行外部程序并解析其输出?

#4

Here is what I use:

这是我使用的:

   /* simply invoke a app, pipe output*/
    pipe = popen(buf, "r" );
    if (pipe == NULL ) {
        printf("invoking %s failed: %s\n", buf, strerror(errno));
        return 1;
    }

    waitfor(10);

    while(!feof(pipe) ) {
        if( fgets( buf, 128, pipe ) != NULL ) {
            printf("%s\n", buf );
        }
    }

    /* Close pipe */
    rc = pclose(pipe);

#1