c - 在管道中获取命令输出，C for Linux

Question

我需要运行 Linux CLI 命令并从 C 获取其标准输出。

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

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

有 popen()，它执行 fork + redirect + exec，但不执行等待，所以我无法获得退出状态。

Answer 1

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().