如何让我的 C++ 代码知道从“system(cmd)”运行的命令是否失败？

Question

Let's assume I am running a unix command using system("foocmd param1") on c++. If foocmd returns "Invalid argument" back to the terminal via stderr, then how do I get my c++ code to know whether foocmd failed?

Here is my attempted solution:

My assumption is that I should check whether anything got returned to stderr by calling the command. To do that, I tried switching over to popen. Currently, this is the way I check. I first output my stderr into a file.

sprintf(cmd, "foocmd param1 2>temp.txt");
system(cmd);

Then I check if temp.txt is empty or not.

But there has to be a better way. Can anyone lend me a hand?

Answer 1

The usual way is to examine the return value of system() :

• If it's zero, the command executed successfully and exited with a status of 0 .
• If it's negative, there was a problem with system() itself, and you can't assume anything.
• If it's positive, then you can use WEXITSTATUS() and related macros to find out how the process exited.

See the system(3) man page for the full details.

---

Most of the time, you are only interested in whether the command says it succeeded:

if (!system(cmd)) {
    syslog(LOG_WARNING, "Command \"%s\" failed", cmd);
    /* maybe some more error handling here */
    goto err_return;
}