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Opening Pipes to and from Processes with popen() and proc_open()

Just as you open a file for writing or reading with fopen(), you can open a pipe to a process with popen(). popen() requires the path to a command and a string representing a mode (read or write). It returns a file pointer that can be used similarly to the file pointer returned by fopen(). You can pass popen() one of two mode flags: "w" to write to the process and "r" to read from it. You cannot, however, both read and write to a process in the same connection.

When you have finished working with the file handle returned by popen(), you must close the connection by calling pclose(), which requires a valid file handler.

Reading from popen() is useful when you want to parse the output ...