All print statements encountered in the block are printed to the file instead of your standard output device. No output will be displayed on your standard output device. This message is sent to a string containing the name of the operating system level command or program to run. The parameter is a block. Any printing performed within the block is sent to the external program as standard input.
Any output generating by the external program is returned and printed by default.
For example, suppose you wanted to use the Unix utility grep to select the numbers in the first 1000 integers that contain the digits 10. The message formatForExcel can be sent to a block and generates tab-delimited output suitable for loading into Excel and other many other packages. The message returns a string. Any print statement encountered while executing this block will be followed by a tab character. Each print statement encountered while evaluating the block will be followed by the octal 377 character, returning the result as a string.