This article explains about touch command with an example in unix.
-a Change the access time of file. Do not change the modification time unless -m is also specified.-c Do not create a specified file if it does not exist. Do not write any diagnostic messages concerning this condition.-m Change the modification time of file. Do not change the access time unless -a is also specified.-r ref_file Use the corresponding times of the file named by ref_file instead of the current time.-t time Use the specified time instead of the current time. time will be a decimal number of the form : [[CC]YY]MMDDhhmm [.SS]-f ref_file Use the corresponding times of the file named by ref_file instead of the current time.file A path name of a file whose times are to be modified.