much more accurate age

files/file-age

@@ -1,5 +1,5 @@
 #!/bin/bash
-
+set -e
 function _help() {
   echo '
 Usage: file-age {file} [units]
@@ -7,27 +7,67 @@ Usage: file-age {file} [units]
   Checks file modification date, and the current time. Prints the age of
   the file in [units].
 
-  [units] is one of S, M, H, d, w, m, y, human
+  [units] is one of S, M, H, d, w, m, y, full, human
           seconds is the default. All values floored.
           month = 30 days
-          year = 365 days
-          human = YY-MM-DD hh:mm:ss
-'
-exit
+          year  = 365 days
+          full  = YY-MM-DD hh:mm:ss
+          human = 3 months 2 days
+  '
+  exit
 }
 for (( i=1; i<=$#; i++ ))
 do  [[ "${!i}" = "-h" ]] && _help
 done
 
 function _human {
-  local T=$1
-  local Y=$((T/60/60/24/365))
-  local m=$((T/60/60/24/30%12))
-  local D=$((T/60/60/24%30))
-  local H=$((T/60/60%24))
-  local M=$((T/60%60))
-  local S=$((T%60))
-  printf '%02d-%02d-%02d %02d:%02d:%02d\n' $Y $m $D $H $M $S
+  file_date=( $( date -r "$STATFILE" +"%Y %m %d %H %M %S" ) )
+  current_date=( $( date +"%Y %m %d %H %M %S" ) )
+  local values=()
+  for (( i=0; $i<${#file_date[@]}; i++ )); do
+    values+=( $(( ${current_date[$i]#0} - ${file_date[$i]#0})) )
+  done
+
+  if [[ ${values[5]} -lt 0 ]]; then
+    values[5]=$(( 60 + ${values[5]} )); values[4]=$(( ${values[4]}  -1 ))
+  fi
+  if [[ ${values[4]} -lt 0 ]]; then
+    values[4]=$(( 60 + ${values[4]} )); values[3]=$(( ${values[3]} -1 ))
+  fi
+  if [[ ${values[3]} -lt 0 ]]; then
+    values[3]=$(( 24 + ${values[3]} )); values[2]=$(( ${values[2]} -1 ))
+  fi
+  if [[ ${values[2]} -lt 0 ]]; then
+    case ${file_date[1]#0} in
+      1|3|5|7|8|10|12) mlen=31;;
+      2) mlen=28;;
+      *) mlen=30;;
+    esac
+    values[2]=$(( $mlen + ${values[2]} ));
+    values[1]=$(( ${values[1]} -1 ))
+  fi
+  if [[ ${values[1]} -lt 0 ]]; then
+    values[1]=$(( 12 + ${values[1]} )); values[0]=$(( ${values[0]} -1 ))
+  fi
+  if [[ "$1" = "full" ]]; then
+    printf '%02d-%02d-%02d %02d:%02d:%02d\n' ${values[@]}
+    return
+  fi
+  local units=( yr mo day hr min sec )
+  if [[ "${file_date[@]}" = "${current_date[@]}" ]]; then
+     printf " 0 sec\n"; return
+  fi
+  for (( i=0; $i<${#values[@]}; i++ )); do
+    if [[ ${values[$i]} -gt 0 ]]; then
+      j=$(( i + 1 ))
+      printf "%2s %-3s" ${values[$i]} ${units[$i]}
+      if [[ $j -lt ${#values[@]} ]]; then
+        printf " %2s %-3s" ${values[$j]} ${units[$j]}
+        break
+      fi
+    fi
+  done
+  printf "\n"
 }
 
 STATFILE="$1"
@@ -44,22 +84,24 @@ age=$(( $now - $created ))
 
 case $UNITS in
   S)
-    echo $age;;
+    echo $age ;;
   M)
-    echo $(( $age / 60 ));;
+    echo $(( $age / 60 )) ;;
   H)
-    echo $(( $age / 3600 ));;
+    echo $(( $age / 3600 )) ;;
   d)
-    echo $(( $age / 86400 ));;
+    echo $(( $age / 86400 )) ;;
   w)
-    echo $(( $age / 604800 ));;
+    echo $(( $age / 604800 )) ;;
   m)
-    echo $(( $age / 2592000 ));;
+    echo $(( $age / 2592000 )) ;;
   y)
-    echo $(( $age / 31536000 ));;
+    echo $(( $age / 31536000 )) ;;
+  full)
+    _human full;;
   human)
-    _human "$age";;
+    _human;;
   *)
     echo Unit $UNITS not recognized.
-    _help;;
+    _help ;;
 esac