Return value of shell-command ?

I've been looking at this piece of code (from package-admin.el) (if (shell-command (concat "gunzip -c " filename " | tar xvf -") buf) 0 1) and it seems to me that "shell-command" always returns 't. The documentation for shell-command doesn't really say anything about the return value. I've tested on both WinNT and Linux and get the same behavior: This is from Linux: ELISP> (shell-command "ls") t ELISP> (shell-command "grep foo bar") t ELISP> (shell-command "grep cgw /etc/passwd") t ELISP> (shell-command "grep foo /etc/passwd") t ELISP> (shell-command "nosuchcommand") t Is this the expected behavior? If shell-command always returns 't what is the test in package-admin trying to do?