如何批量删除Linux mail中的Cron邮件
我在 cron 中设置了每天定时运行 Linux中国 的选题脚本。然后由于cron会将任务的执行结果通过邮件通知用户，这样一来过了一段时间后我的 mail box 中就充满了 CRON 发来邮箱了。
看了网上的一些资料，我知道可以通过 echo 'd *'|mail 来删除所有 mail box 中的邮件，但是这样会把非 CRON 的邮件也删掉，这不是我想要的。
好在翻阅了一下 man mail 发现 d 命令后面可以通过直接跟 发件人地址 或 /关键字 的方式删除指定发件人的邮件，或删除标题中包含 关键字 的邮件。
由于所有的 CRON 发送的邮件都以 (Cron Daemon) 作为发件人，因此可以通过 echo '"(Cron Daemon)"'|mail 来删除所有 CRON 发出的邮件（这里不要忘了括号外的双引号，因为 () 在指定邮件的语法中有特殊意义）
那么若我只是想删除某个 CRON 任务发送的邮件又该怎么办呢？
CRON 发送的邮件的标题格式一般都是这样的 Cron <主机名> CRON命令.
echo -n |mail
Heirloom Mail version 12.5 7/5/10. Type ? for help. "/var/spool/mail/lujun9972": 11 messages 10 unread >U 1 (Cron Daemon) Mon May 25 15:03 26/964 "Cron <lujun9972@VM_0_8_centos> date" U 2 (Cron Daemon) Mon May 25 15:04 26/964 "Cron <lujun9972@VM_0_8_centos> date" U 3 (Cron Daemon) Mon May 25 15:05 26/964 "Cron <lujun9972@VM_0_8_centos> date" U 4 (Cron Daemon) Mon May 25 15:06 26/964 "Cron <lujun9972@VM_0_8_centos> date" U 5 (Cron Daemon) Mon May 25 15:07 26/964 "Cron <lujun9972@VM_0_8_centos> date" U 6 (Cron Daemon) Mon May 25 15:08 26/964 "Cron <lujun9972@VM_0_8_centos> date" 7 (Cron Daemon) Mon May 25 15:09 26/965 "Cron <lujun9972@VM_0_8_centos> date" U 8 (Cron Daemon) Mon May 25 15:10 26/964 "Cron <lujun9972@VM_0_8_centos> date" U 9 (Cron Daemon) Mon May 25 15:11 26/964 "Cron <lujun9972@VM_0_8_centos> date" U 10 (Cron Daemon) Mon May 25 15:12 26/964 "Cron <lujun9972@VM_0_8_centos> date" U 11 (Cron Daemon) Mon May 25 15:13 26/964 "Cron <lujun9972@VM_0_8_centos> date" Held 11 messages in /var/spool/mail/lujun9972
因此，我们可以通过 echo 'd /命令关键字'|mail 来删除某个特定任务的邮件，比如下面命令删除 date 命令产生的邮件：
echo 'd /date' |mail echo -n |mail
No mail for lujun9972
mail 命令中关于指定邮件的语法特别灵活，下面说明摘取自 man mail
man mail |sed -n '/Specifying messages/,/Replying to or originating mail/p'
Specifying messages
Commands such as print and delete can be given a list of message num‐
bers as arguments to apply to a number of messages at once. Thus
`delete 1 2' deletes messages 1 and 2, while `delete 1-5' deletes mes‐
sages 1 through 5. In sorted or threaded mode (see the sort and thread
commands), `delete 1-5' deletes the messages that are located between
(and including) messages 1 through 5 in the sorted/threaded order, as
shown in the header summary. The following special message names
exist:
:n All new messages.
:o All old messages (any not in state read or new).
:u All unread messages.
:d All deleted messages (for the undelete command).
:r All read messages.
:f All `flagged' messages.
:a All answered messages (cf. the markanswered variable).
:t All messages marked as draft.
:k All `killed' messages.
:j All messages classified as junk.
. The current message.
; The message that was previously the current message.
, The parent message of the current message, that is the message
with the Message-ID given in the `In-Reply-To:' field or the
last entry of the `References:' field of the current message.
- The next previous undeleted message, or the next previous
deleted message for the undelete command. In sorted/threaded
mode, the next previous such message in the sorted/threaded
order.
+ The next undeleted message, or the next deleted message for the
undelete command. In sorted/threaded mode, the next such mes‐
sage in the sorted/threaded order.
^ The first undeleted message, or the first deleted message for
the undelete command. In sorted/threaded mode, the first such
message in the sorted/threaded order.
$ The last message. In sorted/threaded mode, the last message in
the sorted/threaded order.
&x In threaded mode, selects the message addressed with x, where x
is any other message specification, and all messages from the
thread that begins at it. Otherwise, it is identical to x. If
x is omitted, the thread beginning with the current message is
selected.
* All messages.
` All messages that were included in the message list for the pre‐
vious command.
/string
All messages that contain string in the subject field (case
ignored). See also the searchheaders variable. If string is
empty, the string from the previous specification of that type
is used again.
address
All messages from address. By default, this is a case-sensitive
search for the complete email address. If the allnet variable
is set, only the local part of the addresses is evaluated for
the comparison. Otherwise if the showname variable is set, a
case-sensitive search for the complete real name of a sender is
performed. The IMAP-style (from address) expression can be used
instead if substring matches are desired.
(criterion)
All messages that satisfy the given IMAP-style SEARCH criterion.
This addressing mode is available with all types of folders; for
folders not located on IMAP servers, or for servers unable to
execute the SEARCH command, mailx will perform the search
locally. Strings must be enclosed by double quotes `"' in their
entirety if they contain white space or parentheses; within the
quotes, only backslash `\' is recognized as an escape character.
All string searches are case-insensitive. When the description
indicates that the `envelope' representation of an address field
is used, this means that the search string is checked against
both a list constructed as
("real name" "source-route" "local-part" "domain-part")
for each address, and the addresses without real names from the
respective header field. Criteria can be nested using parenthe‐
ses.
(criterion1 criterion2 ... criterionN)
All messages that satisfy all of the given criteria.
(or criterion1 criterion2)
All messages that satisfy either criterion1 or criterion2, or
both. To connect more than two criteria using `or', (or) speci‐
fications have to be nested using additional parentheses, as
with `(or a (or b c))'; `(or a b c)' means ((a or b) and c).
For a simple `or' operation of independent criteria on the low‐
est nesting level, it is possible to achieve similar effects by
using three separate criteria, as with `(a) (b) (c)'.
(not criterion)
All messages that do not satisfy criterion.
(bcc string)
All messages that contain string in the `envelope' representa‐
tion of the Bcc: field.
(cc string)
All messages that contain string in the `envelope' representa‐
tion of the Cc: field.
(from string)
All messages that contain string in the `envelope' representa‐
tion of the From: field.
(subject string)
All messages that contain string in the Subject: field.
(to string)
All messages that contain string in the `envelope' representa‐
tion of the To: field.
(header name string)
All messages that contain string in the specified Name: field.
(body string)
All messages that contain string in their body.
(text string)
All messages that contain string in their header or body.
(larger size)
All messages that are larger than size (in bytes).
(smaller size)
All messages that are smaller than size (in bytes).
(before date)
All messages that were received before date; date must be in the
form d[d]-mon-yyyy, where d[d] is the day of the month as one or
two digits, mon is the name of the month—one of `Jan', `Feb',
`Mar', `Apr', `May', `Jun', `Jul', `Aug', `Sep', `Oct', `Nov',
or `Dec', and yyyy is the year as four digits; e.g.
"30-Aug-2004".
(on date)
All messages that were received on the specified date.
(since date)
All messages that were received since the specified date.
(sentbefore date)
All messages that were sent on the specified date.
(senton date)
All messages that were sent on the specified date.
(sentsince date)
All messages that were sent since the specified date.
() The same criterion as for the previous search. This specifica‐
tion cannot be used as part of another criterion. If the previ‐
ous command line contained more than one independent criterion,
the last of those criteria is used.
A practical method to read a set of messages is to issue a from command
with the search criteria first to check for appropriate messages, and
to read each single message then by typing ``' repeatedly.
Replying to or originating mail
