在Linux平台找出某个目录下创建时间最早的文件，测试验证脚本结果是否准确的过程中发现一个很有意思的现象，stat命令在一些平台下Birth字段有值，而在一些平台则为空值，如下所示：
RHEL 8.7下， XFS文件系统
[mysql@mysqlu02 ~]$ more /etc/redhat-release
Red Hat Enterprise Linux release 8.7 (Ootpa)
[mysql@mysqlu02 ~]$ touch test.txt
[mysql@mysqlu02 ~]$ stat test.txt
File: test.txt
Size: 0 Blocks: 0 IO Block: 4096 regular empty file
Device: fd05h/64773d Inode: 144 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 801/ mysql) Gid: ( 800/ mysql)
Access: 2023-05-06 17:09:44.428050549 +0800
Modify: 2023-05-06 17:09:44.428050549 +0800
Change: 2023-05-06 17:09:44.428050549 +0800
Birth: 2023-05-06 17:09:44.428050549 +0800
RHEL 7.9 XFS文件系统
[oracle@KerryDB ~]$ more /etc/redhat-release
Red Hat Enterprise Linux Server release 7.9 (Maipo)
[oracle@KerryDB ~]$ touch test.txt
[oracle@KerryDB ~]$ stat test.txt
File: ‘test.txt’
Size: 0 Blocks: 0 IO Block: 4096 regular empty file
Device: fd03h/64771d Inode: 4238838 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 700/ oracle) Gid: ( 600/oinstall)
Access: 2023-05-06 17:03:42.964517675 +0800
Modify: 2023-05-06 17:03:42.964517675 +0800
Change: 2023-05-06 17:03:42.964517675 +0800
Birth: -
[oracle@KerryDB ~]$
stat命令的Birth字段表示文件的创建时间，该属性是ext4的新功能（当然也适用于xfs文件系统），也称为crtime或btime，但是当前两个测试环境的文件系统为xfs,之前也在xfs文件系统中测试过，发现xfs不支持creation time. 但是从xfs v5开始，xfs已经支持creation time，文档[1]中已有阐述,如下所示：
/* version 5 filesystem (inode version 3) fields start here */
__le32 di_crc;
__be64 di_changecount;
__be64 di_lsn;
&n