What does the command mean in linux

在linux中，凡是在字符操作界面中输入能够完成特定操作和任务的字符串都可以称为命令；命令通常只代表实现某一类功能的程序的名称。命令格式为“命令字 选项 参数”，选项包含段格式选项和长格式选项，段格式选项使用“-”符号引导后面通常跟一个字母，长格式选项使用“--”符号引导通常后面接完整单词。

本教程操作环境：linux7.3系统、Dell G3电脑。

一、命令行格式

1.1、何为命令？

• 在Linux操作系统中，凡是在字符操作界面中输入能够完成特定操作和任务的字符串都可以称为命令
• 命令通常只代表实现某一类功能的程序的名称

命令的格式：命令字 +选项+参数（中间用空格隔开）

选项包含段格式选项和长格式选项，段格式选项使用“-”符号引导后面通常跟一个字母，长格式选项使用“--”符号引导通常后面接完整单词

1.2、获得命令帮助

help：

[root@localhost ~]# help echo
#内部命令查看帮助
echo: echo [-neE] [参数 ...]
    将参数写到标准输出。

    在标准输出上显示 ARG 参数后跟一个换行。

    选项：
      -n    不要追加换行
      -e    启用下列反斜杠转义的解释
      -E    显式地抑制对于反斜杠转义的解释

    `echo' 对下列反斜杠字符进行转义：
      \a    警告（响铃）
      \b    退格
      \c    抑制更多的输出
      \e    转义字符
      \f    格式提供
      \n    换行
      \r    回车
      \t    横向制表符
      \v    纵向制表符
      \\    反斜杠
      \0nnn    以 NNN （八进制）为 ASCII 码的字符。 NNN 可以是
        0到3个八进制数字
      \xHH    以 HH （十六进制）为值的八比特字符。HH可以是
        一个或两个十六进制数字

    退出状态：
    返回成功除非有写错误发生。

--help （查看外部命令帮助）

[root@localhost ~]# ls --help

man

[root@localhost ~]# whatis ls
ls (1)               - 列目录内容
ls (1p)              - list directory contents
[root@localhost ~]# whatis passwd# 可以查看命令的章节
passwd (5)           - (未知的主题)
sslpasswd (1ssl)     - compute password hashes
passwd (1)           - update user's authentication tokens
[root@localhost ~]#

info

[root@localhost
 ~]# info ls

二、目录操作

 [root@localhost ~]# pwd                 //显示当前路径2 /root
 [root@localhost ~]# cd /bin
 [root@localhost bin]# pwd [-lp]        // -p 显示真实路径
 /bin
 [root@localhost bin]#

2.1、cd

命令（cd）	效果
~	切换到当前用户的宿主目录（家目录）
-	到前一次目录
.（一个点号）	以当前工作目录为起点
.. (两个点号）	以当前目录的上一级目录为起点

2.2、ls

格式：ls [选项] [文件或目录]

选项	效果	实操
-l	以长格式显示文件和目录列表	1 [root@localhost ~]# ls -l
-a	显示全部包括隐藏文件	1 [root@localhost ~]# ls -a
-A	显示全部文件或隐藏文件，但不包括 . 和 ..	1 [root@localhost ~]# ls -A
-d	仅列出目录本身，而不是列出目录内的文件数据	1 [root@localhost ~]# ls -d
-h	人性化显示	1 [root@localhost ~]# ls -h
-R	递归显示该目录及该目录的子目录下的所有内容	1 [root@localhost ~]# ls -R
--color	显示颜色	1 [root@localhost ~]# ls --color
-S	以文件容量大小排序	1 [root@localhost ~]# ls -S
-i	indoe号	1 [root@localhost ~]# ls -i

Note:

ls is generally not used alone. Options must be added, otherwise all files in the current folder will be displayed. Excessive number of files may cause a crash

ls can be used with wildcards to filter the required files

2.3. Wildcards

The role of wildcards: match names in files and fuzzy search files

##A~Z (uppercase) [123]Any number among 123[a-z]Any lowercase letter# from a~z #[0-9]##\[^zhao]

Symbol

Effect

?

# Matches one character Example: f? .txt (file starting with f)

*

Match all non-hidden characters, but not hidden files

##{1....10}

1~10

##{a...z}or [[:lower:]]

a~z (lowercase)

{A....Z} or [[:upper:]]

0~9 Any number

escape character (Indicates the original meaning)

Match all characters in the list except z, h, a, o (can be deduced by analogy)

##[[:digit: ]]

Any number is equivalent to 0~9

实操，列几个例子

ls -a *

[root@localhost ~]# ls -a *
{1...10}.txt  anaconda-ks.cfg  elsfk.sh  initial-setup-ks.cfg
# 本来ls -a 表示显示隐藏文件，和通配符 * 一起使用后表示不显示隐藏文件

ls [[:digit:]]
[root@localhost ~]# touch 1 2 3             #创建 1 2 3
 [root@localhost ~]# ls [[:digit:]]          #显示0-9任意的数字
1 2 3                                       #1 2 3 被显示

2.4、alias 命令别名

• alias 命令别名="命令"
• unalias 删除别名
• \+别名命令 显示原始命令
• alias 直接显示所有别名

[root@localhost dev]# alias myvim=vim
# 设置vim的别名myvim
[root@localhost dev]# unalias myvim
# 删除别名
[root@localhost dev]# myvim
bash: myvim: 未找到命令...

2.5、du（disk usage）

选项	说明	效果
-a	统计占用时的所有文件
-h	人性化显示（以kb计数不显示单位）
-s	只统计所占用空间总的大小
--max-depth=n	最大显示到第n层
--exclude	不计入统计

du和ls

• du：统计的当前文件占磁盘的大小，不足4k按4k算

• ls：看到的是真是大小

相关推荐：《Linux视频教程》

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