The Bits 2.0

They are many reasons why I wanted to get this meter working in Linux. But whatever your reason is, this guide is for you.

Screenshot of QtDMM 0.8.13 reading of the N56FU. This screenshot was captured from an Asus EeePC 900 running Ubuntu 9.10.

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Ever wanted to grab the output of a command via C++?

In PHP, we are all very familiar with @exec and popen, but what about C++?

Try this:

string cmd = “/usr/bin/netstat -na”;
string OutString;
FILE *FileStream;
char stdbuffer[1024];
FileStream = popen(cmd.c_str(), “r”);
while (fgets(stdbuffer, 1024, FileStream) != NULL)
OutString.append(stdbuffer);
pclose(FileStream);

• The first 3 lines are variable declarations.
• This is followed by popen command which opens a pipe to the external program. r here means to read from the program output.
• We will now use a 1024 character buffer to read the pipe until a null terminator is encountered.
• Remember to close the process pipe once you’re done!

You ask: “What if I want to have the stderr captured as well?”. No problem! Just add:

2>&1

to the back of your command, just like how you would do it in BASH.

cron is probably one of the most useful services in the UNIX world. It is a time-based scheduling service that executes commands at a set interval.

Most flavours of Linux should have cron bundled. Unfortunately, not every distribution has the same method of configuration. The following example is based on CentOS 5, a popular enterprise web server distribution based on the Red Hat Enterprise Linux.

The configuration file for cron is stored in /etc/crontab. This file stores a list of commands to execute at a certain time interval you set.

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