命令在什么时候使用。这里我知道可以使用它来建立空文件。
如：
[OK_008@CentOS4 ~]$ touch aa --建立一个aa的文件
[OK_008@CentOS4 ~]$ ls -l --Full-time --在Linux中大小写是很敏感的，就如c语言一样。
ls: unrecognized option `--Full-time'
Try `ls --help' for more information.
[OK_008@CentOS4 ~]$ ls -l --full-time --显示列表
total 12
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:11:49.000000000 +0800 aa
drwxrwxr-x 2 OK_008 OK_008 4096 2007-09-28 17:05:35.000000000 +0800 OK008Filed
[OK_008@CentOS4 ~]$ touch {bb.txt,cc.txt,dd.txt}
[OK_008@CentOS4 ~]$ ls -l --full-time
total 24
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:11:49.000000000 +0800 aa
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:28.000000000 +0800 bb.txt
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:28.000000000 +0800 cc.txt
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:28.000000000 +0800 dd.txt --注意这一行的时间
drwxrwxr-x 2 OK_008 OK_008 4096 2007-09-28 17:05:35.000000000 +0800 OK008Filed
[OK_008@CentOS4 ~]$ touch {bb,cc,dd} --touch命令还可以一次建立多个空文件
[OK_008@CentOS4 ~]$ ls -l --full-time
total 36
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:11:49.000000000 +0800 aa
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:52.000000000 +0800 bb
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:28.000000000 +0800 bb.txt
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:52.000000000 +0800 cc
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:28.000000000 +0800 cc.txt
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:52.000000000 +0800 dd
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:28.000000000 +0800 dd.txt
drwxrwxr-x 2 OK_008 OK_008 4096 2007-09-28 17:05:35.000000000 +0800 OK008Filed
[OK_008@CentOS4 ~]$ touch {dd.txt,ee.txt} --这里重新建立多个文件，注意的是dd.txt与上前面代码写dd.txt的时间显示。
[OK_008@CentOS4 ~]$ ls -l --full-time
total 40
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:11:49.000000000 +0800 aa
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:52.000000000 +0800 bb
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:28.000000000 +0800 bb.txt
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:52.000000000 +0800 cc
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:28.000000000 +0800 cc.txt
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:12:52.000000000 +0800 dd
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:13:13.000000000 +0800 dd.txt --注意这一行的时间
-rw-rw-r-- 1 OK_008 OK_008 0 2007-09-28 17:13:13.000000000 +0800 ee.txt
drwxrwxr-x 2 OK_008 OK_008 4096 2007-09-28 17:05:35.000000000 +0800 OK008Filed
[OK_008@CentOS4 ~]$
[OK_008@CentOS4 ~]$ rm aa bb bb.txt cc cc.txt dd dd.txt ee.txt --删除刚才建立的几个空文件
[OK_008@CentOS4 ~]$ ls
OK008Filed
可能这一点就说明touch命令的作用，是于它的修改意义还得参考资料和实践中才能知道了。