C++/Linux run an external command and get output

[Red Squirrel]

What is a way in C++ to run a Linux shell command (basically equivalent to typing it in the standard shell environment) and get the output?

I know with system() I can run a command, but there is no way to get the output unless I specificly pipe it to a file then read that file. I'm looking for a way to do it on the fly.

 

[iCyborg]

Can you take a look at popen() and see if it does what you want?

 

[Markbnj]

You want standard output (stdout). In Windows you can use an option to the CreateProcess call to redirect standard output. I'm not sure what the right method is in Linux.

 

[Red Squirrel]

Can you take a look at popen() and see if it does what you want?

Checking this out right now, I think that may do what I need. Thanks.

Edit: yep it works!

 

[bobross419]

I'm assuming that C++ is similar to Perl in this regard, but those system calls are much more expensive than the same actions performed in code. If its something that will be run quite frequently and doesn't require you to rewrite an entire package it might be beneficial to source dive the other package and see if you can get it working in code.

 

[Red Squirrel]

Yeah normally I would not do it that way, but this is for a monitoring program where data comes from the output of various commands such as cat, sed etc... so the full command is put as part of the config file for each monitor. Using this method I can monitor literally anything by just putting the right command, or script. In this case ms differences don't really matter.

There's also the security issue where if someone maliciously has access to the config files puts something like rm -rf / then the app will execute it, but this is meant to run on a stand alone system that nobody should have access to.

 

[mv2devnull]

Qt does have a "QProcess" class, but learning to use Qt takes some effort.