Accidents Will Happen 19If Dennis and Ken had a Selectric instead of a Teletype, we’d probably be
typing “copy” and “remove” instead of “cp” and “rm.”^1 Proof again that
technology limits our choices as often as it expands them.
After more than two decades, what is the excuse for continuing this tradi-
tion? The implacable force of history, AKA existing code and books. If a
vendor replaced rm by, say, remove, then every book describing Unix
would no longer apply to its system, and every shell script that calls rm
would also no longer apply. Such a vendor might as well stop implement-
ing the POSIX standard while it was at it.
A century ago, fast typists were jamming their keyboards, so engineers
designed the QWERTY keyboard to slow them down. Computer key-
boards don’t jam, but we’re still living with QWERTY today. A century
from now, the world will still be living with rm.
Accidents Will Happen................................................................
Users care deeply about their files and data. They use computers to gener-
ate, analyze, and store important information. They trust the computer to
safeguard their valuable belongings. Without this trust, the relationship
becomes strained. Unix abuses our trust by steadfastly refusing to protect
its clients from dangerous commands. In particular, there is rm, that most
dangerous of commands, whose raison d’etre is deleting files.
All Unix novices have “accidentally” and irretrievably deleted important
files. Even experts and sysadmins “accidentally” delete files. The bill for
lost time, lost effort, and file restoration probably runs in the millions of
dollars annually. This should be a problem worth solving; we don’t under-
stand why the Unixcenti are in denial on this point. Does misery love com-
pany that much?
Files die and require reincarnation more often under Unix than under any
other operating system. Here’s why:
- The Unix file system lacks version numbers.
(^1) Ken Thompson was once asked by a reporter what he would have changed about
Unix if he had it all to do over again. His answer: “I would spell creat with an ‘e.’”