The Ruby Programming Language

Calling the OS

Ruby supports a number of global functions for interacting with the operating system to execute programs, fork new processes, handle signals, and so on. Ruby was initially developed for Unix-like operating systems, and many of these OS-related functions reflect that heritage. By their very nature, these functions are less portable than most others, and some may not be implemented at all on Windows and other non-Unix platforms. The subsections that follow describe some of the most commonly used of the OS-dependent functions. Functions, such a syscall, that are particularly low-level or platform-dependent are not covered here.

Invoking OS Commands

The Kernel.` method expects a single string argument representing an OS shell command. It starts a subshell and passes the specified text to it. The return value is the text printed to standard output. This method is typically invoked using special syntax; it is invoked on string literals surrounded by backquotes or on string literals delimited with %x (see Backtick command execution). For example:

os = `uname`             # String literal and method invocation in one
os = %x{uname}           # Another quoting syntax
os = Kernel.`("uname")   # Invoke the method explicitly

This method does not simply invoke the specified executable; it invokes a shell, which means that shell features such as filename wildcard expansion are available:

files = `echo *.xml`

Another way to start a process and read its output is with the Kernel.open function. This method is ...