catheadsed 三盟友

Posted 2020-11-13 qianxiaoruofeng

在linux 中我们必不可少的会使用到这三个命令
他们有什么作用呢？
就是查看文档了，但他的功能远不止于此

来我们学习一下吧
cat

[root@ESProbe ~]# cat --help
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.

GNU coreutils online help: http://www.gnu.org/software/coreutils/
For complete documentation, run: info coreutils ‘cat invocation‘

-b 显示行号

[root@ESProbe ~]# cat -b /etc/passwd
1 root?0:0:root:/root:/bin/bash
2 bin?1:1:bin:/bin:/sbin/nologin
3 daemon?2:2:daemon:/sbin:/sbin/nologin
4 adm?3:4:adm:/var/adm:/sbin/nologin
5 lp?4:7:lp:/var/spool/lpd:/sbin/nologin
6 sync?5:0:sync:/sbin:/bin/sync
7 shutdown?6:0:shutdown:/sbin:/sbin/shutdown
8 halt?7:0:halt:/sbin:/sbin/halt
9 mail?8:12:mail:/var/spool/mail:/sbin/nologin
10 operator?11:0:operator:/root:/sbin/nologin
11 games?12??games:/usr/games:/sbin/nologin
12 ftp?14:50:FTP User:/var/ftp:/sbin/nologin
13 nobody?99:99:Nobody:/:/sbin/nologin
14 systemd-network?192:192:systemd Network Management:/:/sbin/nologin
15 dbus?81:81:System message bus:/:/sbin/nologin
16 polkitd?999:998:User for polkitd:/:/sbin/nologin
17 sshd?74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
18 postfix?89:89::/var/spool/postfix:/sbin/nologin
19 es?1000:1000::/home/es:/bin/bash
-A 显示所有字符
[root@ESProbe ~]# cat -A /etc/passwd
root?0:0:root:/root:/bin/bash$
bin?1:1:bin:/bin:/sbin/nologin$
daemon?2:2:daemon:/sbin:/sbin/nologin$
adm?3:4:adm:/var/adm:/sbin/nologin$
lp?4:7:lp:/var/spool/lpd:/sbin/nologin$
sync?5:0:sync:/sbin:/bin/sync$
shutdown?6:0:shutdown:/sbin:/sbin/shutdown$
halt?7:0:halt:/sbin:/sbin/halt$
mail?8:12:mail:/var/spool/mail:/sbin/nologin$
operator?11:0:operator:/root:/sbin/nologin$
games?12??games:/usr/games:/sbin/nologin$
ftp?14:50:FTP User:/var/ftp:/sbin/nologin$
nobody?99:99:Nobody:/:/sbin/nologin$
systemd-network?192:192:systemd Network Management:/:/sbin/nologin$
dbus?81:81:System message bus:/:/sbin/nologin$
polkitd?999:998:User for polkitd:/:/sbin/nologin$
sshd?74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin$
postfix?89:89::/var/spool/postfix:/sbin/nologin$
es?1000:1000::/home/es:/bin/bash$

-E 显示结束符结尾多了一个(符号 [root@ESProbe ~]# cat -E /etc/passwd root:x:0:0:root:/root:/bin/bash)
bin?1:1:bin:/bin:/sbin/nologin$
daemon?2:2:daemon:/sbin:/sbin/nologin$
adm?3:4:adm:/var/adm:/sbin/nologin$
lp?4:7:lp:/var/spool/lpd:/sbin/nologin$
sync?5:0:sync:/sbin:/bin/sync$
shutdown?6:0:shutdown:/sbin:/sbin/shutdown$
halt?7:0:halt:/sbin:/sbin/halt$
mail?8:12:mail:/var/spool/mail:/sbin/nologin$
operator?11:0:operator:/root:/sbin/nologin$
games?12??games:/usr/games:/sbin/nologin$
ftp?14:50:FTP User:/var/ftp:/sbin/nologin$
nobody?99:99:Nobody:/:/sbin/nologin$
systemd-network?192:192:systemd Network Management:/:/sbin/nologin$
dbus?81:81:System message bus:/:/sbin/nologin$
polkitd?999:998:User for polkitd:/:/sbin/nologin$
sshd?74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin$
postfix?89:89::/var/spool/postfix:/sbin/nologin$
es?1000:1000::/home/es:/bin/bash$

head

[root@ESProbe ~]# head --help
Usage: head [OPTION]... [FILE]...
Print the first 10 lines of each FILE to standard output.
With more than one FILE, precede each with a header giving the file name.
With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.
-c, --bytes=[-]K print the first K bytes of each file;
with the leading ‘-‘, print all but the last
K bytes of each file
-n, --lines=[-]K print the first K lines instead of the first 10;
with the leading ‘-‘, print all but the last
K lines of each file
-q, --quiet, --silent never print headers giving file names
-v, --verbose always print headers giving file names
--help display this help and exit
--version output version information and exit

K may have a multiplier suffix:
b 512, kB 1000, K 1024, MB 10001000, M 10241024,
GB 100010001000, G 102410241024, and so on for T, P, E, Z, Y.

GNU coreutils online help: http://www.gnu.org/software/coreutils/
For complete documentation, run: info coreutils ‘head invocation‘

eg:查看开头到第二行
[root@ESProbe ~]# head -n 2 /etc/passwd
root?0:0:root:/root:/bin/bash
bin?1:1:bin:/bin:/sbin/nologin

eg:查看前5-10 行内容
[root@ESProbe ~]# cat -n /etc/passwd | head -10 | tail -6
5 lp?4:7:lp:/var/spool/lpd:/sbin/nologin
6 sync?5:0:sync:/sbin:/bin/sync
7 shutdown?6:0:shutdown:/sbin:/sbin/shutdown
8 halt?7:0:halt:/sbin:/sbin/halt
9 mail?8:12:mail:/var/spool/mail:/sbin/nologin
10 operator?11:0:operator:/root:/sbin/nologin

sed

[root@ESProbe ~]# sed --help
Usage: sed [OPTION]... {script-only-if-no-other-script} [input-file]...

-n, --quiet, --silent
suppress automatic printing of pattern space
-e script, --expression=script
add the script to the commands to be executed
-f script-file, --file=script-file
add the contents of script-file to the commands to be executed
--follow-symlinks
follow symlinks when processing in place
-i[SUFFIX], --in-place[=SUFFIX]
edit files in place (makes backup if SUFFIX supplied)
-c, --copy
use copy instead of rename when shuffling files in -i mode
-b, --binary
does nothing; for compatibility with WIN32/CYGWIN/MSDOS/EMX (
open files in binary mode (CR+LFs are not treated specially))
-l N, --line-length=N
specify the desired line-wrap length for the `l‘ command
--posix
disable all GNU extensions.
-r, --regexp-extended
use extended regular expressions in the script.
-s, --separate
consider files as separate rather than as a single continuous
long stream.
-u, --unbuffered
load minimal amounts of data from the input files and flush
the output buffers more often
-z, --null-data
separate lines by NUL characters
--help
display this help and exit
--version
output version information and exit

If no -e, --expression, -f, or --file option is given, then the first
non-option argument is taken as the sed script to interpret. All
remaining arguments are names of input files; if no input files are
specified, then the standard input is read.

GNU sed home page: http://www.gnu.org/software/sed/.
General help using GNU software: http://www.gnu.org/gethelp/.
E-mail bug reports to: [e-mail].
Be sure to include the word sed‘‘ somewhere in theSubject:‘‘ field.

sed -n ‘70,75p‘ date.log 输出第70行到第75行的内容

sed -n ‘6p;260,400p; ‘ 文件名 输出第6行 和 260到400行

sed -n 5p 文件名 输出第5行