cat

一、作用

 linux的一个文本输出命令，通常用于查看文件内容

二、选项

• -n 显示行号
• -E 显示回车符
• -b 对非空输出行编号
  

  三、实例

  ``` [root@xxxx:/etc ]# cat -n /etc/yum.repos.d/CentOS-fasttrack.repo 1 #CentOS-fasttrack.repo 2
  3 [fasttrack] 4 name=CentOS-7 - fasttrack 5 mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=fasttrack&infra=$infra 6 #baseurl=http://mirror.centos.org/centos/$releasever/fasttrack/$basearch/ 7 gpgcheck=1 8 enabled=0 9 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

```
[root@mysql opt]# cat -E /etc/yum.repos.d/CentOS-Base.repo 
# CentOS-Base.repo$
#$
# The mirror system uses the connecting IP address of the client and the$
# update status of each mirror to pick mirrors that are updated to and$
# geographically close to the client.  You should use this for CentOS updates$
# unless you are manually picking other mirrors.$
#$
# If the mirrorlist= does not work for you, as a fall back you can try the $
# remarked out baseurl= line instead.$

[root@localhost network-scripts]# cat 1.txt 
1  this is line 1
     2  this is line 2
     3  log2 this is line 1
     4  log2 this is line 2
     5  log2 this is line 3
//更多请阅读：https://www.yiibai.com/linux/cat.html


[root@localhost network-scripts]# cat 2.txt 
1232312
[root@localhost network-scripts]# cat -n 1.txt 2.txt 
     1    1  this is line 1
     2         2  this is line 2
     3         3  log2 this is line 1
     4         4  log2 this is line 2
     5         5  log2 this is line 3
     6    //更多请阅读：https://www.yiibai.com/linux/cat.html
     7    
     8    
     9    1232312

[root@localhost network-scripts]# cat -b 1.txt 2.txt >log.log 
[root@localhost network-scripts]# cat log.log 
     1    1  this is line 1
     2         2  this is line 2
     3         3  log2 this is line 1
     4         4  log2 this is line 2
     5         5  log2 this is line 3
     6    //更多请阅读：https://www.yiibai.com/linux/cat.html


     7    1232312
[root@localhost network-scripts]# cat  1.txt 2.txt >log.log 
[root@localhost network-scripts]# cat log.log 
1  this is line 1
     2  this is line 2
     3  log2 this is line 1
     4  log2 this is line 2
     5  log2 this is line 3
//更多请阅读：https://www.yiibai.com/linux/cat.html


1232312

[root@localhost network-scripts]# cat >log.txt <<EOF
> jasaid
> lkk
> EOF
[root@localhost network-scripts]# cat log.txt 
jasaid
lkk