Page 33

The backquoted command wc -l /etc/passwd seen in the page's last command line should actually be wc -l < /etc/passwd.

The issue is that wc -l prints out filenames as well as line counts when filenames are supplied on the command line. Here, only the line count is wanted.

Page 44

Contrary to Table 2.2, bash has no string equivalents to the numeric -le and -ge operators. The >= and <= operators listed in Table 2.2 do not exist.

The > and < operators do exist. However, they must be backslash-escaped or double bracketed to prevent them from being interpreted as I/O redirection characters.

Page 45

The loop variable in the example for loop is actually called script. The text refers to it as file.

Pages 51 and 52

The regular expression shown on pages 51–52 for matching various spellings of Moammar Gadhafi's name is OK as originally printed. However, the accompanying text does not explain why the ([dtz][dhz]?)+ group (a component of the last name match) allows repetition.

The + is there to accommodate variants such as Quadhdhafi. Really, that fragment should be ([dtz][dhz]?){1,2} so that only one or two occurrences are permissible.

More generally, it's worth noting that this regex is permissive. Not every string that it matches is a legitimate spelling of Gadhafi's name. However, it should match all legitimate spellings.

Page 153

The cross-reference in the last line of the first paragraph under The setuid and setgid bits points to the wrong place.

The referenced material is on page 105, not page 106.

Page 466

The route commands at the bottom of the page are shell commands, not excerpts from a startup script as the surrounding text might imply.

The # character indicates root's shell prompt, not the comment character used in shell scripts.

Page 574

DNS Punycode names begin with xn--, not xf-- as stated in the text.

Page 808

In addition to having its own conventions, Debian's version of Exim configuration uses the m4 preprocessor.

We don't describe the Debian system in this book.

Page 817

There are two errors on this page.

In the sentence "The sender's address is not checked because many user agents get confused by error returns," replace "sender's address" with "recipient's address."

The paragraph that starts "We next check the destination domain..." claims that DKIM verification is not performed during this step. That is incorrect; DKIM is in fact enabled.

Page 821

It is not entirely accurate to say that "If a message receives a pass or decline from all the routers in the sequence, it is bounced as an unroutable address."

In fact, Exim may either bounce or reject such messages, depending on the context.

Page 827

Contrary to the statement in the Debugging section, exim does fork when given the -d flag. However, it does not detach itself from the control terminal.

Page 852

In the configuration file excerpt, the line that sets dkim_selector should do a lookup on $dkim_domain, not $sender_address_domain as shown.