how to get linux command output string and output status in c++

Question

I want to get a Linux command's output string as well as command output status in a C++ program. I am executing Linux commands in my application.

for example: Command:

rmdir abcd

Command output string:

rmdir: failed to remove `abcd': No such file or directory

Command Status:

1 (Which means command has been failed)

I tried using Linux function system() which gives the output status, and function popen() which gives me output string of a command, but neither function gives me both the output string and output status of a Linux command.

Answer 1

The output string is in standard output or standard error descriptor (1 or 2, respectively).

You have to redirect these streams (take a look at dup and dup2 function) to a place, where you can read them (for example - a POSIX pipe).

In C I'd do something like this:

int pd[2];
int retValue;
char buffer[MAXBUF] = {0};
pipe(pd);
dup2(pd[1],1);
retValue = system("your command");
read(pd[0], buffer, MAXBUF);

Now, you have (a part of) your output in buffer and the return code in retValue.

Alternatively, you can use a function from exec (i.e. execve) and get the return value with wait or waitpid.

Update: this will redirect only standard output. To redirect standard error, use dup2(pd[1],1).

Answer 2

The simplest solution is to use system, and to redirect standard out and standard error to a temporarly file, which you can delete later.