Linux获取命令帮助信息有哪些方式
在 Linux 系统中，获取命令帮助信息是一项非常重要的技能，它可以帮助用户快速了解命令的用法、参数和选项等内容。以下是几种常见的获取命令帮助信息的方式：
一、使用 man 命令
`man`（manual 的缩写）命令是 Linux 系统中最常用的获取命令帮助信息的方式之一。它可以显示命令的手册页，其中包含了命令的详细说明、用法示例、参数列表等信息。
例如，要获取`ls`命令的帮助信息，可以在终端中输入`man ls`命令。这将会打开`ls`命令的手册页，显示如下内容：
```
LS(1) User Commands LS(1)
NAME
ls - list directory contents
SYNOPSIS
ls [OPTION]... [FILE]...
DESCRIPTION
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.
-a, --all
do not hide entries starting with.
-A, --almost-all
do not list implied. and..
-b, --escape
print C-style escapes for nongraphic characters.
-B, --ignore-backups
do not list implied entries ending with ~.
-c, --time=ctime
with -lt: sort by, and show, ctime (time of last status change);
with -l: show ctime and sort by name; otherwise: sort by ctime, newest first.
-d, --directory
list directory entries instead of contents, and do not dereference symbolic links.
-f, --format=single-column
list one file per line.
-F, --classify
append indicator (one of */=>@|) to entries.
-g, --group
with -l: display the group names as well as the owner.
-h, --human-readable
with -l: print sizes in human readable format (e.g., 1K 234M 2G).
-i, --inode
print the index number of each file.
-l, --long
use a long listing format.
-L, --dereference
follow symbolic links only if they are listed.
-n, --numeric-uid-gid
print user and group IDs numerically.
-N, --literal
do not print ~ and.. for entries.
-o, --omit-dir-names
do not list names of directories.
-p, --indicator-style=slash
append / to directories.
-q, --hide-control-chars
print non-printing characters using ^ and M- notation.
-r, --reverse
reverse order while sorting.
-s, --size
print the allocated size of each file, in blocks.
-t, --time=atime
with -lt: sort by, and show, atime (time of last access);
with -l: show atime and sort by name; otherwise: sort by atime, newest first.
-T, --tabsize=N
assume tab stops at every N columns.
-u, --time=atime
with -lt: sort by, and show, atime (time of last access);
with -l: show atime and sort by name; otherwise: sort by atime, newest first.
-U, --unsorted
do not sort; list entries in directory order.
-v, --version-sort
sort alphabetically, but compare numeric suffixes first.
-w, --width=N
set output width to N columns.
-X, --sort=extension
sort by file extension.
-1, --one-file-system
list only files on one file system.
--color[=WHEN]
control whether color is used to distinguish file types.
WHEN can be 'never','always', or 'auto'.
--help
display this help and exit.
--version
output version information and exit.
EXAMPLES
ls
list the contents of the current directory.
ls -l
list the contents of the current directory in long format.
ls -a
list all files in the current directory, including hidden files.
ls -R
list the contents of all subdirectories recursively.
AUTHOR
GNU coreutils online help version 8.32
Written by David MacKenzie and others.
COPYRIGHT
Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.
SEE ALSO
dircolors(1), vdir(1), vdircolors(1), find(1), glob(7), pathchk(1), printf(1), test(1), touch(1).
```
通过阅读`man`页面，用户可以了解`ls`命令的各种选项和用法，以及如何根据自己的需求进行定制。`man`页面通常非常详细，包含了命令的所有相关信息，是学习和使用 Linux 命令的重要参考资料。
二、使用 info 命令
`info`命令是另一种获取命令帮助信息的方式，它提供了更加结构化和交互式的帮助文档。`info`页面通常包含了命令的概述、详细说明、示例、相关命令等内容，并且可以通过链接和索引进行导航。
要获取`ls`命令的`info`页面，可以在终端中输入`info ls`命令。这将会打开`ls`命令的`info`页面，显示如下内容：
```
Node: ls invocation, Contents: [Top] [Index] [Search] [Next] [Previous] [Home] [Up]
ls invocation
(ls invocation)
Summary: List information about files.
Description:
The `ls' command lists information about the files in the current directory or the specified directory. It can display file names, sizes, timestamps, permissions, and other attributes.
Options:
- a: List all files, including hidden files.
- A: List all files except. and..
- b: Print non-printable characters in octal escape format.
- B: Do not list implied entries ending with ~.
- c: Sort by file status change time.
- d: List directories instead of their contents.
- f: List files in a single column.
- F: Append file type indicators to file names.
- g: Print group names instead of user names.
- h: Print human-readable file sizes.
- i: Print file inode numbers.
- l: Use a long listing format.
- L: Follow symbolic links.
- m: List files separated by commas.
- n: Print user and group names in numeric form.
- o: Do not print group information.
- p: Append / to directories.
- q: Print non-printable characters using quote characters.
- r: Reverse the order of sorting.
- s: Print file sizes in blocks.
- t: Sort by file modification time.
- u: Sort by file access time.
- v: Sort lexicographically, using version sort.
- x: Sort by file names within directories.
- 1: List one file per line.
Examples:
- ls: List files in the current directory.
- ls -l: List files in long format.
- ls -a: List all files in the current directory.
- ls -R: Recursively list files in subdirectories.
See Also:
dir(1), vdir(1), find(1), stat(1), file(1)
```
与`man`页面相比，`info`页面更加注重组织结构和交互性，用户可以通过点击链接和使用索引来快速找到自己需要的信息。`info`页面还提供了一些额外的功能，如搜索、注释和参考资料等，使得获取帮助信息更加方便和高效。
三、使用 --help 选项
许多 Linux 命令都支持`--help`选项，它可以显示命令的简短帮助信息，包括命令的用法、选项和参数等内容。
例如，要获取`ls`命令的`--help`信息，可以在终端中输入`ls --help`命令。这将会显示如下内容：
```
Usage: ls [OPTION]... [FILE]...
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.
-a, --all do not hide entries starting with.
-A, --almost-all do not list implied. and..
-b, --escape print C-style escapes for nongraphic characters
-B, --ignore-backups do not list implied entries ending with ~
-c, --time=ctime with -lt: sort by, and show, ctime (time of last status change);
with -l: show ctime and sort by name; otherwise: sort by ctime,
newest first
-d, --directory list directory entries instead of contents, and do not
dereference symbolic links
-f, --format=single-column
list one file per line
-F, --classify append indicator (one of */=>@|) to entries
-g, --group with -l: display the group names as well as the owner
-h, --human-readable with -l: print sizes in human readable format (e.g., 1K 234M 2G)
-i, --inode print the index number of each file
-l, --long use a long listing format
-L, --dereference follow symbolic links only if they are listed
-n, --numeric-uid-gid
print user and group IDs numerically
-N, --literal do not print ~ and.. for entries
-o, --omit-dir-names do not list names of directories
-p, --indicator-style=slash
append / to directories
-q, --hide-control-chars
print non-printing characters using ^ and M- notation
-r, --reverse reverse order while sorting
-s, --size print the allocated size of each file, in blocks
-t, --time=atime with -lt: sort by, and show, atime (time of last access);
with -l: show atime and sort by name; otherwise: sort by atime,
newest first
-T, --tabsize=N assume tab stops at every N columns
-u, --time=atime with -lt: sort by, and show, atime (time of last access);
with -l: show atime and sort by name; otherwise: sort by atime,
newest first
-U, --unsorted do not sort; list entries in directory order
-v, --version-sort sort alphabetically, but compare numeric suffixes first
-w, --width=N set output width to N columns
-X, --sort=extension sort by file extension
-1, --one-file-system list only files on one file system
--color[=WHEN] control whether color is used to distinguish file types
WHEN can be 'never', 'always', or 'auto'
--help display this help and exit
--version output version information and exit
GNU coreutils online help version 8.32
Written by David MacKenzie and others.
Copyright © 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.
```
`--help`选项提供了一个简洁明了的命令帮助信息，适合快速了解命令的基本用法和选项。对于一些简单的命令，`--help`选项通常就足够了。
四、使用在线文档和社区资源
除了上述本地的命令帮助方式，还可以通过在线文档和社区资源获取更详细和最新的命令帮助信息。
Linux 官方网站提供了丰富的文档和资源，包括命令手册、教程、FAQ 等。可以通过访问[https://www.gnu.org/software/coreutils/manual/coreutils.html](https://www.gnu.org/software/coreutils/manual/coreutils.html)来获取`coreutils`命令集的详细文档，其中包含了许多常用命令的帮助信息。
Linux 社区也是获取命令帮助的重要来源。可以通过在搜索引擎中输入相关命令加上“Linux 教程”、“Linux 命令帮助”等关键词，找到大量的在线教程和社区讨论。这些资源通常由经验丰富的用户和开发者提供，能够提供更深入和实用的帮助。
例如，在[https://www.linux.com/tutorials/command-line/](https://www.linux.com/tutorials/command-line/)网站上，有许多关于 Linux 命令的教程和指南，可以帮助用户更好地理解和使用各种命令。
在 Linux 系统中，获取命令帮助信息有多种方式可供选择。用户可以根据自己的需求和习惯，灵活使用`man`命令、`info`命令、`--help`选项以及在线文档和社区资源，以快速获取所需的命令帮助信息，提高工作效率。
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