1.cat
文本查看。查看指定文件的内容
[root@catyuan ~]# cat /etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
-n 显示行号
[root@catyuan ~]# cat -n /etc/hosts
1 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
2 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
2.tac
按逆序查看文件内容
[root@catyuan ~]# tac /etc/hosts
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
3.more
分页查看文件内容，支持向后翻。空格（下一页）、回车（下一行）。
[root@catyuan ~]# more /var/log/boot.log
4.less
支持前后翻。空格（下一页）、方向键（上下回翻）、q键（退出查看）
[root@catyuan ~]# less /var/log/boot.log
5.head
查看文件前多少行，默认为十行。
[root@catyuan ~]# head /var/log/boot.log
Welcome to CentOS
Starting udev: [ OK ]
Setting hostname catyuan: [ OK ]
Setting up Logical Volume Management: [ OK ]
Checking filesystems
Checking all file systems.
[/sbin/fsck.ext4 (1) -- /] fsck.ext4 -a /dev/vda1
/dev/vda1: clean, 32206/2621440 files, 476339/10485248 blocks
[ OK ]
Remounting root filesystem in read-write mode: [ OK ]
-n 显示文件前几行内容
[root@catyuan ~]# head -n 2 /var/log/boot.log
Welcome to CentOS
Starting udev: [ OK ]
6.tail
查看文件后n行，默认为十行
[root@catyuan ~]# tail /var/log/boot.log
Cloud-init v. 0.7.6a4 finished at Wed, 07 Nov 2018 10:49:56 +0000. Datasource DataSourceAliYun. Up 12.59 seconds
Starting sshd: [ OK ]
Starting ntpd: [ OK ]
Aegis is running
Starting postfix: [ OK ]
Starting crond: [ OK ]
Starting atd: [ OK ]
aliyun-service stop/waiting
aliyun-service start/running, process 1593
finished
-n 显示文件末尾n行内容
[root@catyuan ~]# tail -n 2 /var/log/boot.log
aliyun-service start/running, process 1593
finished
-f 查看文件后并不退出，滚动显示追加内容
[root@catyuan ~]# tail -f /var/log/boot.log
7.wc
显示文件的行、单词与字节信息
[root@catyuan ~]# wc /var/log/boot.log
67 570 4566 /var/log/boot.log
-c 显示文件的字节信息
[root@catyuan ~]# wc -c /var/log/boot.log
4566 /var/log/boot.log
-l 显示文件行数
[root@catyuan ~]# wc -l /var/log/boot.log
67 /var/log/boot.log
-w 显示文件单词个数
[root@catyuan ~]# wc -w /var/log/boot.log
570 /var/log/boot.log
8.grep
查找关键词并输出有关键词的这一行。
[root@catyuan ~]# grep 23 test
23456
12345
[root@catyuan ~]# cat test
23456
12345
adcdvcfv
kkkthshss
-i 忽略大小写
-v 取反匹配
-w 匹配单词，匹配的是单词，而不是字母
--color 显示颜色
9.echo
显示一行的指定文本
[root@catyuan ~]# echo hello
hello
给空白文件里添加内容
[root@catyuan ~]# echo 123 > test
[root@catyuan ~]# cat test
123
给文件里追加内容
[root@catyuan ~]# echo 456 >> test
[root@catyuan ~]# cat test
123
456
注意追加内容时，是两个>>，否则会覆盖
[root@catyuan ~]# cat test
123
456
[root@catyuan ~]# echo 123456 > test
[root@catyuan ~]# cat test
123456