Liunx中 ls -al 释义
ls 选项
[root@node2 ~]# ls --help
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.
Mandatory arguments to long options are mandatory for short options too.
-a, --all do not ignore entries starting with . ===> 不忽略当前目录下所有，即显示当前目录中所有
-A, --almost-all do not list implied . and .. ===> 不以长整型输出当前目录且显示隐藏目录，并隐藏 . 和 .. 目录
--author with -l, print the author of each file
-b, --escape print C-style escapes for nongraphic characters
--block-size=SIZE scale sizes by SIZE before printing them; e.g.,
'--block-size=M' prints sizes in units of
1,048,576 bytes; see SIZE format below
-B, --ignore-backups do not list implied entries ending with ~
-c with -lt: sort by, and show, ctime (time of last
modification of file status information);
with -l: show ctime and sort by name;
otherwise: sort by ctime, newest first
-C list entries by columns
--color[=WHEN] colorize the output; WHEN can be 'never', 'auto',
or 'always' (the default); more info below
-d, --directory list directories themselves, not their contents ===> 列出目录本身，而不是它们的内容
-D, --dired generate output designed for Emacs' dired mode
-f do not sort, enable -aU, disable -ls --color
-F, --classify append indicator (one of */=>@|) to entries ===> 可使用特殊字符，即正则
--file-type likewise, except do not append '*'
--format=WORD across -x, commas -m, horizontal -x, long -l,
single-column -1, verbose -l, vertical -C
--full-time like -l --time-style=full-iso
-g like -l, but do not list owner
--group-directories-first
group directories before files;
can be augmented with a --sort option, but any
use of --sort=none (-U) disables grouping
-G, --no-group in a long listing, don't print group names
-h, --human-readable with -l, print sizes in human readable format
(e.g., 1K 234M 2G)
--si likewise, but use powers of 1000 not 1024
-H, --dereference-command-line
follow symbolic links listed on the command line
--dereference-command-line-symlink-to-dir
follow each command line symbolic link
that points to a directory
--hide=PATTERN do not list implied entries matching shell PATTERN
(overridden by -a or -A)
--indicator-style=WORD append indicator with style WORD to entry names:
none (default), slash (-p),
file-type (--file-type), classify (-F)
-i, --inode print the index number of each file ===> 打印每个文件的索引号
-I, --ignore=PATTERN do not list implied entries matching shell PATTERN ===> 不列出与 shell PATTERN 匹配的隐含条目
-k, --kibibytes default to 1024-byte blocks for disk usage ===> 默认为 1024 字节块用于磁盘使用
-l use a long listing format
-L, --dereference when showing file information for a symbolic
link, show information for the file the link
references rather than for the link itself
-m fill width with a comma separated list of entries
-n, --numeric-uid-gid like -l, but list numeric user and group IDs
-N, --literal print raw entry names (don't treat e.g. control
characters specially)
-o like -l, but do not list group information
-p, --indicator-style=slash
append / indicator to directories
-q, --hide-control-chars print ? instead of nongraphic characters
--show-control-chars show nongraphic characters as-is (the default,
unless program is 'ls' and output is a terminal)
-Q, --quote-name enclose entry names in double quotes
--quoting-style=WORD use quoting style WORD for entry names:
literal, locale, shell, shell-always, c, escape
-r, --reverse reverse order while sorting
-R, --recursive list subdirectories recursively
-s, --size print the allocated size of each file, in blocks
-S sort by file size
--sort=WORD sort by WORD instead of name: none (-U), size (-S),
time (-t), version (-v), extension (-X)
--time=WORD with -l, show time as WORD instead of default
modification time: atime or access or use (-u)
ctime or status (-c); also use specified time
as sort key if --sort=time
--time-style=STYLE with -l, show times using style STYLE:
full-iso, long-iso, iso, locale, or +FORMAT;
FORMAT is interpreted like in 'date'; if FORMAT
is FORMAT1<newline>FORMAT2, then FORMAT1 applies
to non-recent files and FORMAT2 to recent files;
if STYLE is prefixed with 'posix-', STYLE
takes effect only outside the POSIX locale
-t sort by modification time, newest first
-T, --tabsize=COLS assume tab stops at each COLS instead of 8
-u with -lt: sort by, and show, access time;
with -l: show access time and sort by name;
otherwise: sort by access time
-U do not sort; list entries in directory order
-v natural sort of (version) numbers within text
-w, --width=COLS assume screen width instead of current value
-x list entries by lines instead of by columns
-X sort alphabetically by entry extension
-1 list one file per line
SELinux options:
--lcontext Display security context. Enable -l. Lines
will probably be too wide for most displays.
-Z, --context Display security context so it fits on most
displays. Displays only mode, user, group,
security context and file name.
--scontext Display only security context and file name.
--help display this help and exit
--version output version information and exit
SIZE is an integer and optional unit (example: 10M is 10*1024*1024). Units
are K, M, G, T, P, E, Z, Y (powers of 1024) or KB, MB, ... (powers of 1000).
Using color to distinguish file types is disabled both by default and
with --color=never. With --color=auto, ls emits color codes only when
standard output is connected to a terminal. The LS_COLORS environment
variable can change the settings. Use the dircolors command to set it.
Exit status:
0 if OK,
1 if minor problems (e.g., cannot access subdirectory),
2 if serious trouble (e.g., cannot access command-line argument).
GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
For complete documentation, run: info coreutils 'ls invocation'
示例
这里主要讲解回显中第三列的数值意思，即 3 18 1 1 1...这些数值的意思
[root@node2 ~]# ls -al
total 32 ===> 第一行，下面会有单独讲的部分
dr-xr-x---. 3 root root 163 Apr 24 15:59 . ===> 第二行
dr-xr-xr-x. 18 root root 236 Apr 13 14:21 .. ===> 第三行
-rw-------. 1 root root 1325 Apr 11 10:24 anaconda-ks.cfg
-rw-------. 1 root root 2248 Apr 24 13:47 .bash_history
-rw-r--r--. 1 root root 18 Dec 29 2013 .bash_logout
-rw-r--r--. 1 root root 176 Dec 29 2013 .bash_profile
-rw-r--r--. 1 root root 176 Dec 29 2013 .bashrc
-rw-r--r--. 1 root root 100 Dec 29 2013 .cshrc
drwx------. 2 root root 29 Apr 13 10:54 .ssh ===> 示例说明目录
-rw-r--r--. 1 root root 129 Dec 29 2013 .tcshrc
-rw-------. 1 root root 3004 Apr 13 14:22 .viminfo
注:
对于目录文件，回显中第三列表示它的第一级子目录的个数。此处看到目录的第三列的值要减2才等于该目录下的子目录的实际个数。
比如这里的.ssh目录下其实是没有子目录，所以应该是0，但它这里却显示2是因为要加上.目录和..目录。
在linux下，.目录表示当前目录，..目录表示上一级目录
下面的回显也可以解释上图中第二行第三列的 . 目录下的3和第二行 .. 目录下的18的意思
因为当前目录下有一个.ssh目录，所以加上.目录和..目录这2个目录就等于3，所以回显中第二行第三列会显示3。
而第三行第三列则对于上一级目录共有16个目录，加上上一级目录的 . 目录和 .. 目录这2个目录，所以这里的第二行显示的是18（如下所示）
对于其他文件，表示指向它的链接文件的个数 ===> 注意要理解这句话！！！
[root@node2 ~]# ls -al / | grep ^d|wc -l
18
[root@node2 ~]# ls -al /
total 16
dr-xr-xr-x. 18 root root 236 Apr 13 14:21 .
dr-xr-xr-x. 18 root root 236 Apr 13 14:21 ..
lrwxrwxrwx. 1 root root 7 Apr 11 10:21 bin -> usr/bin
dr-xr-xr-x. 5 root root 4096 Apr 14 08:22 boot
drwxr-xr-x. 21 root root 3420 Apr 24 13:55 dev
drwxr-xr-x. 76 root root 8192 Apr 24 13:55 etc
drwxr-xr-x. 2 root root 6 Apr 11 2018 home
lrwxrwxrwx. 1 root root 7 Apr 11 10:21 lib -> usr/lib
lrwxrwxrwx. 1 root root 9 Apr 11 10:21 lib64 -> usr/lib64
drwxr-xr-x. 2 root root 6 Apr 11 2018 media
drwxr-xr-x. 2 root root 6 Apr 11 2018 mnt
drwxr-xr-x. 3 root root 19 Apr 13 15:44 opop
drwxr-xr-x. 2 root root 6 Apr 11 2018 opt
dr-xr-xr-x. 156 root root 0 Apr 24 13:55 proc
dr-xr-x---. 3 root root 163 Apr 24 15:59 root
drwxr-xr-x. 26 root root 840 Apr 24 15:35 run
lrwxrwxrwx. 1 root root 8 Apr 11 10:21 sbin -> usr/sbin
drwxr-xr-x. 2 root root 6 Apr 11 2018 srv
dr-xr-xr-x. 13 root root 0 Apr 24 13:55 sys
drwxrwxrwt. 10 root root 195 Apr 24 15:59 tmp
drwxr-xr-x. 13 root root 155 Apr 11 10:21 usr
drwxr-xr-x. 19 root root 267 Apr 11 10:25 var
total 32由来
把上面的图拿下来，方便查看和讲解
[root@node2 ~]# ls -als
total 32
0 dr-xr-x---. 3 root root 163 Apr 24 17:59 .
0 dr-xr-xr-x. 18 root root 236 Apr 13 14:21 ..
4 -rw-------. 1 root root 1325 Apr 11 10:24 anaconda-ks.cfg
4 -rw-------. 1 root root 2248 Apr 24 13:47 .bash_history
4 -rw-r--r--. 1 root root 18 Dec 29 2013 .bash_logout
4 -rw-r--r--. 1 root root 176 Dec 29 2013 .bash_profile
4 -rw-r--r--. 1 root root 176 Dec 29 2013 .bashrc
4 -rw-r--r--. 1 root root 100 Dec 29 2013 .cshrc
0 drwx------. 2 root root 29 Apr 13 10:54 .ssh
4 -rw-r--r--. 1 root root 129 Dec 29 2013 .tcshrc
4 -rw-------. 1 root root 3416 Apr 24 16:42 .viminfo
注: 要明白该项是什么意思，首先要了解一个数据块（Block）的概念，linux的数据存储是以block(块)为单位的。
-s以块大小为单位列出所有文件的大小
文件系统在格式化时就规范好了block的大小，在ext2/ext3的环境下这个block不变
每一个 block 仅能容纳一个文件/目录，所以如果block大小为4K ，而单一个文件/目录只有1K则会有3K的空间被浪费。而那个total会记录的则是4K的容量
[root@node2 ~]# ll -h
total 4.0K
-rw-------. 1 root root 1.3K Apr 11 10:24 anaconda-ks.cfg
注: 使用上述命令查询即只查询的是一个块，所以是4K
计算一共浪费了多少空间的计算方法：
4*8=32K # 上述使用-s选项出来的是每个文件所占的块大小，乘8是总共占的block大小
1325占用1个block，所以总共耗去4Kbytes
2248占用1个block，所以总共耗去4Kbytes
18占用1个block，所以总共耗去4Kbytes
176占用1个block，所以总共耗去4Kbytes ===> 低于4096都是占一个block
176占用1个block，所以总共耗去4Kbytes
100占用1个block，所以总共耗去4Kbytes
129占用1个block，所以总共耗去4Kbytes
3416占用1个block，所以总共耗去4Kbytes
(1325+2248+18+176+176+100+29+129+3416)/1024=7K
32K-7K=25K
一共浪费了25K左右的空间
其他
在大多数的linux shell窗口中，还能用颜色来区分不同文件的属性：（指回显中最后一列，文件名/目录名）
灰白色表示普通文件；
亮绿色表示可执行文件；
亮红色表示压缩文件；
灰蓝色表示目录；
亮蓝色表示链接文件；
亮黄色表示设备文件；
~]# ll －t 是降序， ll －t ｜ tac 是升序
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