Bash的基础知识man手册 Posted 2021-05-02 细说Linux tags: 篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了Bash的基础知识man手册相关的知识,希望对你有一定的参考价值。 Bash的基础知识man手册 Bash是一个为GNU计划编写的Unix Shell。它是许多Linux平台内定Shell,还有许多传统UNIX上用的Shell,如tcsh、csh、ash、bsh、ksh等。Bash是大多数Linux系统上默认的Shell,本章将介绍Bash的基础知识。 2.1 man手册 Linux man中的man就是manual的缩写,中文说法是手册。在Linux中,man手册就是用来查看系统中自带的各种参考手册。通过查看man手册,可以从中获取到各种命令、文件、库函数等帮助信息。本节将介绍从man手册。 使用man文件是很容易的,这里首先介绍下它的语法格式及相关参数。man命令的语法格式如下所示: · man [SECTION NUMBER] MAN PAGE NAME 以上命令中,两个选项的含义如下所示: q SECTION NUMBER:表示man手册页的章节号。 q MAN PAGE NAME:表示man手册名称,通常是命令、系统或库本身的名称。例如,如果查找man命令的手册页,执行命令如下所示: · man 1 man 在以上命令中,1表示告诉man命令为第1节,而man参数后面的命令就man手册页的名称。 Man手册页章节号是根据它们自己的规范定义的,主要分为几个部分。如下所示: q 1:普通命令用这个段查找使用在命令行的命令信息。在上面这个命令中,使用它来查找关于man文件的信息。 q 2:系统调用:即由内核提供的函数。 q 3:C库函数。对于C语言开发,该文档是非常有用的,并且开发者使用开发语言作为C延伸工具,如Python。它将显示参数相关的信息,头文件的定义、行为和基本C库函数调用的目的。 q 4:特殊文件,也就是各种设备文件。这些文件通常保存在/dev/目录中,如字符设备、伪终端等。 q 5:文件格式和转化。该文档包含了Linux系统中文件的格式。如密码文件passwd,该手册页将会说明这个文件中各个字段的含义。 q 6:游戏和屏幕保护。该文档中包含关于游戏和屏幕保护程序信息。 q 7:杂集。该文档中包括各种命令信息和其它信息。 q 8:系统管理员命令和守护进程。该文档中命令和系统守护进程只能由管理员使用。 man手册的页面布局是标准化的,包含一个特定部分的集合。man手册页的每个部分都包含了描述、系统调用或库函数。下面分别介绍一下在man文件中目的相同的部分,如下所示: q Name:表示命令、函数、系统调用或文件格式的名称。 q Synopsis:表示命令、函数、系统调用、文件格式等语法格式。 q Description:对命令功能的描述 q Examples:表示对命令如何使用给出的例子。 q See also:表示参考文档、Web页面及与该程序有关的其它程序。 为了验证man手册的语法格式及内容格式等,下面举几个例子作为验证。 【实例2-1】查看本机伪终端的man手册页。执行命令如下所示: · android@localhost:~$ man 4 pts 执行以上命令后,将显示如下所示的信息: · PTS(4) LinuxProgrammer'sManual PTS(4) · NAME · ptmx, pts - pseudoterminal master and slave · DESCRIPTION · The file /dev/ptmx is a character filewith major number 5 and minor · number 2, usually of mode 0666 andowner.group of root.root. It is · used to create a pseudoterminal master andslave pair. · When a process opens /dev/ptmx, itgets a file descriptor for a pseu‐ · doterminal master (PTM), and apseudoterminal slave (PTS) device is · created in the /dev/ptsdirectory. Each file descriptor obtained by · opening /dev/ptmx is an independent PTM withits own associated PTS, · whose path can be found by passing thedescriptor to ptsname(3). · Before opening the pseudoterminal slave,you must pass the master's · file descriptor to grantpt(3) and unlockpt(3). · Once both the pseudoterminal master and slaveare open, the slave pro‐ · vides processes with aninterface that is identical to that of a real · terminal. · …… · FILES · /dev/ptmx, /dev/pts/* · NOTES · The Linux support for the above (known as UNIX98 pseudoterminal nam‐ · ing) is done using the devpts filesystem, that should be mounted on · /dev/pts. · Before this UNIX 98 scheme, master pseudoterminals were called · /dev/ptyp0, ... and slave pseudoterminals/dev/ttyp0, ... and one · needed lots of preallocated device nodes. · SEE ALSO · getpt(3), grantpt(3), ptsname(3), unlockpt(3),pty(7) · COLOPHON · This page is part of release 3.44 of theLinux man-pages project. A · description of theproject, and information about reporting bugs, can · be found athttp://www.kernel.org/doc/man-pages/. 从以上输出的信息中,可以看到该手册页共有七部分,如主题、文件名称、文件保存位置、参考资料等。在输出信息的左上角可以看到显示了PTS(4)。其中,PTS表示手册名称,(4)表示手册位于第四章节。最后,按下q键退出man手册页 【实例2-2】查看passwd文件的man手册页。执行命令如下所示: · android@localhost:~$ man 5 passwd 执行以上命令后,将输出如下所示的信息: · PASSWD(5) FileFormats andConversions PASSWD(5) · NAME · passwd - the password file · DESCRIPTION · /etc/passwd contains one line for each useraccount, with seven fields · delimited by colons (“:”). These fields are: · · login name · · optional encrypted password · · numerical user ID · · numerical group ID · · user name or comment field · · user home directory · · optional user command interpreter · The encrypted password field may be blank, inwhich case no password is · required to authenticate as the specified loginname. However, some · applications which read the /etc/passwd filemay decide not to permit · any access at all if the password field isblank. If the password field · is a lower-case “x”, then theencrypted password is actually stored in · the shadow(5) file instead; there must be acorresponding line in the · /etc/shadow file, or else the user account isinvalid. If the password · field is any other string, then it will betreated as an encrypted · password, as specified by crypt(3). · The comment field is used by various systemutilities, such as · finger(1). · The home directory field provides the name ofthe initial working · directory. The login program uses thisinformation to set the value of · the $HOME environmental variable. · The command interpreter field provides the nameof the user's command · language interpreter, or the name of theinitial program to execute. · The login program uses this information to setthe value of the $SHELL · environmental variable. If this field is empty,it defaults to the · value /bin/sh. · FILES · /etc/passwd · User account information. · /etc/shadow · optional encrypted password file · /etc/passwd- · Backup file for /etc/passwd. · Note that this file is used bythe tools of the shadow toolsuite, · but not by all user and passwordmanagement tools. · SEE ALSO · crypt(3), getent(1), getpwnam(3), login(1),passwd(1), pwck(8), · pwconv(8), pwunconv(8), shadow(5), su(1),sulogin(8). · shadow-utils4.1.5.1 05/25/2012 PASSWD(5) 从以上输出信息中,可以看到passwd文件中共有七个字段,并且每个字段使用“冒号:”分割。具体每个字段的作用,在该文档中都有详细介绍。在Linux系统中也有passwd命令,如果查看该命令的帮助信息,执行命令如下所示: · android@localhost:~$ man 1 passwd 输出信息如下所示: · PASSWD(1) UserCommands PASSWD(1) · NAME · passwd - change user password · SYNOPSIS · passwd [options] [LOGIN] · DESCRIPTION · The passwd command changes passwords for useraccounts. A normal user · may only change the password for his/her ownaccount, while the · superuser may change the password for anyaccount. passwd also changes · the account or associated password validityperiod. · …… · OPTIONS · The options which apply to the passwd commandare: · -a, --all · This option can be used only with-S and causes show status for all · users. · -d, --delete · Delete a user's password (make itempty). This is a quick way to · disable a password for anaccount. It will set the named account · passwordless. · -e, --expire · Immediately expire an account'spassword. This in effect can force · a user to change his/her passwordat the user's next login. · -h, --help · Display help message and exit. · -i, --inactive INACTIVE · This option is used to disable anaccount after the password has · been expired for a number ofdays. After a user account has had an · expired password for INACTIVE days,the user may no longer sign on · to the account. · …… · CAVEATS · Password complexity checking may vary from siteto site. The user is · urged to select a password as complex as he orshe feels comfortable · with. · Users may not be able to change their passwordon a system if NIS is · enabled and they are not logged into the NISserver. · passwd uses PAM to authenticate users and tochange their passwords. · FILES · /etc/passwd · User account information. · /etc/shadow · Secure user account information. · /etc/pam.d/passwd · PAM configuration for passwd. · EXIT VALUES · The passwd command exits with the followingvalues: · 0 · success · 1 · permission denied · 2 · invalid combination of options · 3 · unexpected failure, nothing done · 4 · unexpected failure, passwd filemissing · 5 · passwd file busy, try again · 6 · invalid argument to option · SEE ALSO · chpasswd(8), passwd(5), shadow(5), usermod(8). · shadow-utils4.1.5.1 05/25/2012 PASSWD(1) 在以上输出信息中,显示了passwd命令的语法格式、选项、描述等信息。从以上的输出信息中,可以发现使用的章节编号不同,显示的帮助文档内容也不同。在以上命令中,也可以不输入章节号1的。因为,man命令默认是从数字较小的手册中寻找相关命令和函数。 以上是关于Bash的基础知识man手册的主要内容,如果未能解决你的问题,请参考以下文章 linux 设置中文版man手册 Linux的bash shell与man查看手册 计算机基础——Linux的bash.shell,help,man命令 计算机基础——Linux的bash.shell,help,man命令 计算机基础——Linux的bash.shell,help,man命令 Linux基础篇一