Changing the date format in a file [closed] - linux

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I'm working on redHat linux.
I've a file which looks like :
$vi filename
Jan,1,00:00:01,someone checked your file
Jan,3,09:38:02,applebee
Jan,16,10:20:03, ****************
Jan,18,03:04:03, ***************
I want the output to look like:
2015/01/01,00:00:01,someone checked your file
2015/01/03,3,09:38:02,applebee
2015/01/16,16,10:20:03, ****************
2015/01/18,03:04:03, ***************
Please help me to do this. Thanks

Answer 1

If you have GNU date, try:
$ awk -F, '{cmd="date -d \""$1" "$2"\" +%Y/%m/%d"; cmd|getline d; print d","$3","$4; close(cmd)}' file
2015/01/01,00:00:01,someone checked your file
2015/01/03,09:38:02,applebee
2015/01/16,10:20:03, ****************
2015/01/18,03:04:03, ***************
This approach cannot be used with the BSD (OSX) version of date because it does not support any comparable -d option.
How it works
awk implicitly loops over lines of input, breaking each line into fields.
-F,
This tells awk to use a comma as the field separator
cmd="date -d \""$1" "$2"\" +%Y/%m/%d"
This creates a string variable, cmd, and contains a date command. I am assuming that you have GNU date.
cmd|getline d
This runs the command and captures the output in variable d.
print d","$3","$4
This prints the output that you asked for.
close(cmd)
This closes the command.