touch - 创建空文件，修改时间
Usage：
Usage: touch [OPTION]... FILE...
Update the access and modification times of each FILE to the current time.
A FILE argument that does not exist is created empty, unless -c or -h
is supplied.
A FILE argument string of - is handled specially and causes touch to
change the times of the file associated with standard output.
Mandatory arguments to long options are mandatory for short options too.
-a change only the access time
-c, --no-create do not create any files
-d, --date=STRING parse STRING and use it instead of current time
-f (ignored)
-h, --no-dereference affect each symbolic link instead of any referenced
file (useful only on systems that can change the
timestamps of a symlink)
-m change only the modification time
-r, --reference=FILE use this file's times instead of current time
-t STAMP use [[CC]YY]MMDDhhmm[.ss] instead of current time
--time=WORD change the specified time:
WORD is access, atime, or use: equivalent to -a
WORD is modify or mtime: equivalent to -m
--help display this help and exit
--version output version information and exit
Note that the -d and -t options accept different time-date formats.
mtime ：modification time （默认）
文件的内容被修改时会更新
ctime ：status time
文件的属性或权限被修改时会更新
atime ： access time
文件的内容被读取时会更新
[root@78063f0fe2e8 etc]# ls -l login.defs
-rw-r--r-- 1 root root 2028 Nov 4 2016 login.defs
[root@78063f0fe2e8 etc]# ls -l login.defs --time=atime
-rw-r--r-- 1 root root 2028 Nov 4 2016 login.defs
[root@78063f0fe2e8 etc]# ls -l login.defs --time=ctime
-rw-r--r-- 1 root root 2028 Apr 20 14:19 login.defs
常用选项：
-a（access） ：仅修改访问时间
-c（）：仅修改文件时间，若文件不存在则不创建新文件
-m（modification）： 仅修改 mtime
-t （time）：想要修改的时间[YYMMDDhhmm]
-d（date）：修改的日期
- 新建空文件
sh-4.2# cd /tmp
sh-4.2# touch testtouch
sh-4.2# ls -l testtouch
-rw-r--r-- 1 root root 0 Apr 21 07:52 testtouch
sh-4.2# ls -l testtouch --time=atime
-rw-r--r-- 1 root root 0 Apr 21 07:52 testtouch
sh-4.2# ls -l testtouch --time=ctime
-rw-r--r-- 1 root root 0 Apr 21 07:52 testtouch
- 修改时间
sh-4.2# cp -a ~/.bashrc bashrc
sh-4.2# ls -l bashrc
-rw-r--r-- 1 root root 176 Dec 29 2013 bashrc
sh-4.2# ls -l bashrc --time=atime
-rw-r--r-- 1 root root 176 Dec 29 2013 bashrc
sh-4.2# ls -l bashrc --time=ctime
-rw-r--r-- 1 root root 176 Apr 21 07:53 bashrc
sh-4.2# touch -d "2 days ago" bashrc
sh-4.2# ls -l bashrc
-rw-r--r-- 1 root root 176 Apr 19 07:55 bashrc
sh-4.2# ls -l bashrc --time=atime
-rw-r--r-- 1 root root 176 Apr 19 07:55 bashrc
sh-4.2# ls -l bashrc --time=ctime
-rw-r--r-- 1 root root 176 Apr 21 07:55 bashrc
sh-4.2# touch -t 1801011000 bashrc
sh-4.2# ls -l bashrc
-rw-r--r-- 1 root root 176 Jan 1 10:00 bashrc
sh-4.2# ls -l bashrc --time=ctime
-rw-r--r-- 1 root root 176 Apr 21 07:57 bashrc
sh-4.2# ls -l bashrc --time=atime
-rw-r--r-- 1 root root 176 Jan 1 10:00 bashrc
cat - concatenate 浏览文件
Usage：
Usage: cat [OPTION]... [FILE]...
Concatenate FILE(s), or standard input, to standard output.
-A, --show-all equivalent to -vET
-b, --number-nonblank number nonempty output lines, overrides -n
-e equivalent to -vE
-E, --show-ends display $ at end of each line
-n, --number number all output lines
-s, --squeeze-blank suppress repeated empty output lines
-t equivalent to -vT
-T, --show-tabs display TAB characters as ^I
-u (ignored)
-v, --show-nonprinting use ^ and M- notation, except for LFD and TAB
--help display this help and exit
--version output version information and exit
With no FILE, or when FILE is -, read standard input.
Examples:
cat f - g Output f's contents, then standard input, then g's contents.
cat Copy standard input to standard output.
常用选项：
-A（All）：显示所有，包括特殊字符，等价于-vET
-v（verbose）：列出看不出来的特殊字符
-T（Tab）：将 Tab 按键以^I 显示出来
-b（blank）：列出行号，空白行不标号
-n（number）：列出行号，空白行也有
-E（End）：将结尾的断行字符$显示出来
sh-4.2# cat /etc/issue
\S
Kernel \r on an \m
sh-4.2# cat -n /etc/issue
1 \S
2 Kernel \r on an \m
3
sh-4.2# cat -b /etc/issue
1 \S
2 Kernel \r on an \m
sh-4.2# cd /tmp
sh-4.2# ls
bashrc mvtest2 testtouch yum.log
ks-script-hE5IPf test.conf tmpk3saal44-ascii.cast
sh-4.2# cat -A test.conf
^Ihello$
this is a test file only...$
sh-4.2# cat -An test.conf
1 ^Ihello$
2 this is a test file only...$
tac - 反向 cat
Usage：
Usage: tac [OPTION]... [FILE]...
Write each FILE to standard output, last line first.
With no FILE, or when FILE is -, read standard input.
Mandatory arguments to long options are mandatory for short options too.
-b, --before attach the separator before instead of after
-r, --regex interpret the separator as a regular expression
-s, --separator=STRING use STRING as the separator instead of newline
--help display this help and exit
--version output version information and exit
tac 没有 -n 选项
[root@78063f0fe2e8 ~]# tac /etc/issue
Kernel \r on an \m
\S
nl - 添加行号显示文件
Usage：
Usage: nl [OPTION]... [FILE]...
Write each FILE to standard output, with line numbers added.
With no FILE, or when FILE is -, read standard input.
Mandatory arguments to long options are mandatory for short options too.
-b, --body-numbering=STYLE use STYLE for numbering body lines
-d, --section-delimiter=CC use CC for separating logical pages
-f, --footer-numbering=STYLE use STYLE for numbering footer lines
-h, --header-numbering=STYLE use STYLE for numbering header lines
-i, --line-increment=NUMBER line number increment at each line
-l, --join-blank-lines=NUMBER group of NUMBER empty lines counted as one
-n, --number-format=FORMAT insert line numbers according to FORMAT
-p, --no-renumber do not reset line numbers at logical pages
-s, --number-separator=STRING add STRING after (possible) line number
-v, --starting-line-number=NUMBER first line number on each logical page
-w, --number-width=NUMBER use NUMBER columns for line numbers
--help display this help and exit
--version output version information and exit
By default, selects -v1 -i1 -l1 -sTAB -w6 -nrn -hn -bt -fn. CC are
two delimiter characters for separating logical pages, a missing
second character implies :. Type \\ for \. STYLE is one of:
a number all lines
t number only nonempty lines
n number no lines
pBRE number only lines that contain a match for the basic regular
expression, BRE
FORMAT is one of:
ln left justified, no leading zeros
rn right justified, no leading zeros
rz right justified, leading zeros
[root@78063f0fe2e8 ~]# nl /etc/issue
1 \S
2 Kernel \r on an \m
[root@78063f0fe2e8 ~]# nl /etc/issue -b a
1 \S
2 Kernel \r on an \m
3
[root@78063f0fe2e8 ~]# nl /etc/issue -b a -n rz
000001 \S
000002 Kernel \r on an \m
000003
[root@78063f0fe2e8 ~]# nl /etc/issue -b a -n ln
1 \S
2 Kernel \r on an \m
3
[root@78063f0fe2e8 ~]# nl /etc/issue -b a -n rn
1 \S
2 Kernel \r on an \m
3
[root@78063f0fe2e8 ~]# nl /etc/issue -b a -n rn -w 3
1 \S
2 Kernel \r on an \m
3
[root@78063f0fe2e8 ~]# nl /etc/issue -b a -n rz -w 3
001 \S
002 Kernel \r on an \m
003
more - 一页一页显示文件内容
Usage：
more: unknown option -help
Usage: more [options] file...
Options:
-d display help instead of ring bell
-f count logical, rather than screen lines
-l suppress pause after form feed
-p do not scroll, clean screen and display text
-c do not scroll, display text and clean line ends
-u suppress underlining
-s squeeze multiple blank lines into one
-NUM specify the number of lines per screenful
+NUM display file beginning from line number NUM
+/STRING display file beginning from search string match
-V output version information and exit
空格：向下翻一页
Enter：向下一行
/字符串：向下查询字符串
q：退出查看
b：往回翻页
less - more 的进阶
略