What is the difference between '<' and '<<' in linux

Difference:

In Linux, > means overwriting the original file content (the date of the file will also be automatically updated), >> means appending the content (it will start a new file) line, the date of the file will also be updated automatically).

(Recommended tutorial: linux tutorial)

Example:

1. Save the results of the history command execution to the history.log file

[root@gxzs-solr1 ~]# history > history.log      （history.log 文件 会自动生成）
[root@gxzs-solr1 ~]# cat history.log

2. Execute the command curl 'xxx' and save the return result in log.log

[root@gx-solr1 ~]# curl 'http://192.168.0.110:8983/solr/scan_detail/admin/file?_=1544066402749&contentType=text/plain;charset=utf-8&file=managed-schema&wt=json' > log.log

3. Execute the command cat /etc/hosts and save the return result in hosts.log中

[root@slave1 ~]# cat /etc/hosts > hosts.log
[root@slave1 ~]# more hosts.log 
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

Note: When using > , when executing a command, a new file following > will be generated each time, replacing the previously generated file (the file creation time will also change accordingly).

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