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为什么这个手册页有今天的日期？

tag-icon • tag-icon unattended-upgrades
为什么这个手册页有今天的日期？

为什么特定man页面（在我的例子中，用于nc命令）会具有今天的日期，而无需我对系统进行任何更新？另外，为什么“无人值守更新”日志没有显示当天的任何特定活动？

2018-03-14 07:47:38,124 INFO Initial blacklisted packages:
2018-03-14 07:47:38,135 INFO Starting unattended upgrades script
2018-03-14 07:47:38,135 INFO Allowed origins are: ['o=LinuxMint,a=qiana-security', 'o=LinuxMintESM,a=qiana']
2018-03-14 07:47:51,767 INFO No packages found that can be upgraded unattended and no pending auto-removals

这是nc手册页的页脚：

BSD                             March 14, 2018                             BSD

这是在 Linux Mint 17 (qiana) 上，基于 Ubuntu 14.04 (trusty)，带有 groff 1.22.2 和 man-db 2.6.7.1。

编辑

请求的命令输出：

  1. man -aw nc

    /usr/share/man/man1/nc_openbsd.1.gz

  2. ls -ld $(man -aw nc)

    -rw-r--r-- 1 root root 5.7K Dec  4  2012 /usr/share/man/man1/nc_openbsd.1.gz

这很奇怪...

  1. dpkg -S $(man -aw nc)？

    netcat-openbsd: /usr/share/man/man1/nc_openbsd.1.gz

  2. type -a man

    man is /usr/bin/man

  3. zgrep docdate $(man -aw nc)

    .Dd $Mdocdate: February 7 2012 $

  4. 添加页脚 strace -f man nc 2>&1 | grep -e '^BSD' -e '"/.*nc'

    ychaouche#ychaouche-PC 14:31:15 ~ $ strace -f man nc 2>&1 | grep -e '^BSD' -e '"/.*nc'
execve("/usr/bin/man", ["man", "nc"], [/* 87 vars */]) = 0
lstat("/usr/share/man/man1/nc.1.gz", {st_mode=S_IFLNK|0777, st_size=25, ...}) = 0
lstat("/usr/share/man/man1/nc.1.gz", {st_mode=S_IFLNK|0777, st_size=25, ...}) = 0
readlink("/usr/share/man/man1/nc.1.gz", "/etc/alternatives/nc.1.gz", 4095) = 25
lstat("/etc/alternatives/nc.1.gz", {st_mode=S_IFLNK|0777, st_size=35, ...}) = 0
readlink("/etc/alternatives/nc.1.gz", "/usr/share/man/man1/nc_openbsd.1"..., 4095) = 35
lstat("/usr/share/man/man1/nc_openbsd.1.gz", {st_mode=S_IFREG|0644, st_size=5756, ...}) = 0
stat("/usr/share/man/man1/nc_openbsd.1.gz", {st_mode=S_IFREG|0644, st_size=5756, ...}) = 0
stat("/usr/share/man/man1/nc_openbsd.1.gz", {st_mode=S_IFREG|0644, st_size=5756, ...}) = 0
open("/usr/share/man/man1/nc_openbsd.1.gz", O_RDONLY) = 3
access("/usr/share/man/man1/nc.1.gz", R_OK) = 0
lstat("/usr/share/man/man1/nc.1.gz", {st_mode=S_IFLNK|0777, st_size=25, ...}) = 0
lstat("/usr/share/man/man1/nc.1.gz", {st_mode=S_IFLNK|0777, st_size=25, ...}) = 0
readlink("/usr/share/man/man1/nc.1.gz", "/etc/alternatives/nc.1.gz", 4095) = 25
lstat("/etc/alternatives/nc.1.gz", {st_mode=S_IFLNK|0777, st_size=35, ...}) = 0
readlink("/etc/alternatives/nc.1.gz", "/usr/share/man/man1/nc_openbsd.1"..., 4095) = 35
lstat("/usr/share/man/man1/nc_openbsd.1.gz", {st_mode=S_IFREG|0644, st_size=5756, ...}) = 0
stat("/usr/share/man/man1/nc_openbsd.1.gz", {st_mode=S_IFREG|0644, st_size=5756, ...}) = 0
stat("/usr/share/man/man1/nc_openbsd.1.gz", {st_mode=S_IFREG|0644, st_size=5756, ...}) = 0
open("/usr/share/man/man1/nc_openbsd.1.gz", O_RDONLY) = 3
stat("/usr/share/man/man1/nc.1.gz", {st_mode=S_IFREG|0644, st_size=5756, ...}) = 0
stat("/usr/share/man/cat1/nc.1.gz", 0x7fffa49c0940) = -1 ENOENT (No such file or directory)
stat("/usr/share/man/man1/nc_openbsd.1.gz", {st_mode=S_IFREG|0644, st_size=5756, ...}) = 0
open("/usr/share/man/man1/nc_openbsd.1.gz", O_RDONLY) = 3
[pid  3878] stat("/usr/share/man/man1/nc_openbsd.1.gz", {st_mode=S_IFREG|0644, st_size=5756, ...}) = 0
[pid  3878] access("/usr/share/man/man1/nc_openbsd.1.gz", R_OK <unfinished ...>
BSD                             March 20, 2018                             BSD

  5. strace -f man nc 2>&1 | grep -vwe -1 | grep -o '"/[^"]*"' | sort -u | grep -v /dev/ | xargs sh -c 'zgrep "March 14" "$@"' sh 2> /dev/null

     no output

    看来日期没有硬编码。可能是生成今天日期的宏。

  6. env | grep -e ROFF -e MAN -e GRO

    SESSION_MANAGER=local/ychaouche-PC:@/tmp/.ICE-unix/2915,unix/ychaouche-PC:/tmp/.ICE-unix/2915
MANDATORY_PATH=/usr/share/gconf/default.mandatory.path

  7. env -i man nc显示今天的日期（2018 年 3 月 20 日）

  8. zcat /usr/share/man/man1/nc_openbsd.1.gz | nroff -mandoc | grep BSD

    ychaouche#ychaouche-PC 06:59:53 ~ $ zcat /usr/share/man/man1/nc_openbsd.1.gz | nroff -mandoc | grep BSD
NC(1)                     BSD General Commands Manual                    NC(1)
BSD                             March 20, 2018                             BSD
ychaouche#ychaouche-PC 07:01:41 ~ $

  9. strace -f man nc 2>&1 | grep -vwe -1 | grep -o '"/[^"]*tmac/[^"]*"' | sort -u | xargs ls -lrtd

    ychaouche#ychaouche-PC 17:26:08 /usr/share/man/man1 $ unalias ls
ychaouche#ychaouche-PC 17:26:12 /usr/share/man/man1 $ unalias xargs
ychaouche#ychaouche-PC 17:26:14 /usr/share/man/man1 $ unalias grep
ychaouche#ychaouche-PC 17:26:16 /usr/share/man/man1 $ strace -f man nc 2>&1 | grep -vwe -1 | grep -o '"/[^"]*tmac/[^"]*"' | sort -u | xargs ls -lrtd
-rw-r--r-- 1 root root  4065 Jan 22  2014 /usr/share/groff/1.22.2/tmac/papersize.tmac
-rw-r--r-- 1 root root  1860 Jan 22  2014 /usr/share/groff/1.22.2/tmac/andoc.tmac
-rw-r--r-- 1 root root    71 Jan 22  2014 /usr/share/groff/1.22.2/tmac/unicode.tmac
-rw-r--r-- 1 root root  1552 Jan 22  2014 /usr/share/groff/1.22.2/tmac/tty.tmac
-rw-r--r-- 1 root root  5183 Jan 22  2014 /usr/share/groff/1.22.2/tmac/tty-char.tmac
-rw-r--r-- 1 root root  1145 Jan 22  2014 /usr/share/groff/1.22.2/tmac/troffrc-end
-rw-r--r-- 1 root root  1387 Jan 22  2014 /usr/share/groff/1.22.2/tmac/troffrc
-rw-r--r-- 1 root root  4729 Jan 22  2014 /usr/share/groff/1.22.2/tmac/pspic.tmac
-rw-r--r-- 1 root root 22042 Jan 22  2014 /usr/share/groff/1.22.2/tmac/mdoc/doc-syms
-rw-r--r-- 1 root root  4048 Jan 22  2014 /usr/share/groff/1.22.2/tmac/mdoc/doc-nroff
-rw-r--r-- 1 root root 29284 Jan 22  2014 /usr/share/groff/1.22.2/tmac/mdoc/doc-common
-rw-r--r-- 1 root root  2250 Jan 22  2014 /usr/share/groff/1.22.2/tmac/latin1.tmac
-rw-r--r-- 1 root root 27860 Jan 22  2014 /usr/share/groff/1.22.2/tmac/hyphen.us
-rw-r--r-- 1 root root 15678 Jan 22  2014 /usr/share/groff/1.22.2/tmac/hyphenex.us
-rw-r--r-- 1 root root  1362 Jan 22  2014 /usr/share/groff/1.22.2/tmac/fallbacks.tmac
-rw-r--r-- 1 root root 73807 Jan 22  2014 /usr/share/groff/1.22.2/tmac/doc.tmac
-rw-r--r-- 1 root root   537 Jan 22  2014 /usr/share/groff/1.22.2/tmac/composite.tmac
-rw-r--r-- 1 root root   704 Jan 22  2014 /usr/share/groff/site-tmac/mdoc.local
ychaouche#ychaouche-PC 17:26:18 /usr/share/man/man1 $

答案1

GNU roff 过去不支持这些：

 .Dd $Mdocdate: February 7 2012 $

OpenBSD 扩展（这里$Mdocdate: ...$是由 CVS（OpenBSD 用于对代码进行版本控制）扩展的 CVS/RCS 关键字以及手动修订的日期），导致当前日期而不是指定的日期被扩展。我可以在 Ubuntu 14.04 上为所有具有此类Mdocdate.

看https://savannah.gnu.org/bugs/?42968实施于https://lists.gnu.org/archive/html/groff-commit/2014-10/msg00092.html（groff 版本 1.22.3）。

对于 MirBSD（现在的 MirOS）的手册页，例如您的paxcpio或mksh，它们使用相同的$Mdocdate: ...$CVS 关键字，您会发现手册页.Dd本身重新定义（包装） mdoc 宏，因此 roff 系统宏不必支持它：

.\"
.\" Implement .Dd with the Mdocdate RCS keyword
.\"
.rn Dd xD
.de Dd
.ie ^G\\$1^G$Mdocdate:^G \{\
.       xD \\$2 \\$3, \\$4
.\}
.el .xD \\$1 \\$2 \\$3 \\$4 \\$5 \\$6 \\$7 \\$8
..
.\"
.\" .Dd must come before definition of .Mx, because when called
.\" with -mandoc, it might implement .Mx itself, but we want to
.\" use our own definition. And .Dd must come *first*, always.
.\"
.Dd $Mdocdate: August 16 2017 $

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