touch - change file timestamps

SYNOPSIS       touch [OPTION]... FILE...DESCRIPTION       Update  the  access  and modification times of each FILE to the current       time.           timestamp更新到当前时间，链接文件需要-h选项才可以       A FILE argument that does not exist is created empty, unless -c  or  -h       is supplied.           文件不存在会被创建       A  FILE  argument  string of - is handled specially and causes touch to       change the times of the file associated with standard output.       Mandatory arguments to long options are  mandatory  for  short  options       too.       -a     change only the access time         改变文件的读取时间记录       -c, --no-create              do not create any files        假如目标文件不存在，不会建立新的文件。与 --no-create 的效果一样       -d, --date=STRING              parse STRING and use it instead of current time        指定时间，字符串的格式见后文       -f     (ignored)        <不使用，是为了与其他 unix 系统的相容性而保留       -h, --no-dereference              affect each symbolic link instead of any referenced file (useful              only on systems that can change the timestamps of a symlink)        可以更改链接文件的timestamps       -m     change only the modification time        改变文件的修改时间记录       -r, --reference=FILE              use this file's times instead of current time        使用参考文件的时间记录，与 --file 的效果一样       -t STAMP              use [[CC]YY]MMDDhhmm[.ss] instead of current time       --time=WORD              change the specified time: WORD is access, atime, or use: equiv‐              alent to -a WORD is modify or mtime: equivalent to -m       --help display this help and exit       --version              output version information and exit       Note that the -d and -t options accept different time-date formats.DATE STRING       The  --date=STRING  is  a mostly free format human readable date string       such as "Sun, 29 Feb 2004 16:21:42 -0800" or "2004-02-29  16:21:42"  or       even  "next Thursday".  A date string may contain items indicating cal‐       endar date, time of day, time zone, day of week, relative  time,  rela‐       tive date, and numbers.  An empty string indicates the beginning of the       day.  The date string format is more complex than is easily  documented       here but is fully described in the info documentation.AUTHOR       Written  by  Paul  Rubin, Arnold Robbins, Jim Kingdon, David MacKenzie,       and Randy Smith.