I was trying to find the time of database backup. Normally i use ls -ltchBut this time i usedls -lrthIt gave me different result for One file and all date-stamps were same for both commands -rw-r----- 1 oracle dba  41M Dec  7 23:59 ctrl_071223-rw-r----- 1 oracle dba  42M Dec  7 20:52 c-4249173797-20121207-00-rw-r----- 1 oracle dba 202M Dec  7 20:52 ALG_OSLPRD_jens9rfr.alg-rw-r----- 1 oracle dba 189M Dec  7 20:52 ALG_OSLPRD_jfns9rfr.alg-rw-r----- 1 oracle dba 140M Dec  7 20:52 ALG_OSLPRD_jgns9rfr.alg-rw-r----- 1 oracle dba 3.0G Dec  7 20:51 BKPOSLPRD_jbns9p1f.F_bkp-rw-r----- 1 oracle dba 4.2G Dec  7 20:46 BKPOSLPRD_jdns9p1f.F_bkp-rw-r----- 1 oracle dba 3.8G Dec  7 20:43 BKPOSLPRD_jcns9p1f.F_bkp[root@pdbosl02 daily]# ls -lrthtotal 12G-rw-r----- 1 oracle dba 3.8G Dec  7 20:43 BKPOSLPRD_jcns9p1f.F_bkp-rw-r----- 1 oracle dba 4.2G Dec  7 20:46 BKPOSLPRD_jdns9p1f.F_bkp-rw-r----- 1 oracle dba 3.0G Dec  7 20:51 BKPOSLPRD_jbns9p1f.F_bkp-rw-r----- 1 oracle dba 140M Dec  7 20:52 ALG_OSLPRD_jgns9rfr.alg-rw-r----- 1 oracle dba 189M Dec  7 20:52 ALG_OSLPRD_jfns9rfr.alg-rw-r----- 1 oracle dba 202M Dec  7 20:52 ALG_OSLPRD_jens9rfr.alg-rw-r----- 1 oracle dba  42M Dec  7 20:52 c-4249173797-20121207-00-rw-r----- 1 oracle dba  41M Dec  7 20:52 ctrl_071223What I'm missing 
Why ls -lrth and ls -ltch gives different results
ls;timestamps
The differences between both commands are:the 2nd listing is sorted in reverse (-r)the 2nd listing uses the modification time stamp as sort key (-t)the 1st listing uses the ctime stamp as sort key (-tc)On UNIX a file has 3 time stamps (atime, ctime, mtime) which are updated under different conditions.To quote the wikipedia article on stat:atime: time of last access (ls -lu),  mtime: time of last modification (ls -l), and  ctime: time of last status change (ls -lc).An example for a status change is changing the permissions of a file.