filename last modification date shell in script

Question

I'm using bash to build a script where I will get a filename in a variable an then with this variable get the file unix last modification date.

I need to get this modification date value and I can't use stat command.

Do you know any way to get it with the common available *nix commands?

Answer 1

Why you shouldn't use ls:

Parsing ls is a bad idea. Not only is the behaviour of certain characters in filenames undefined and platform dependant, for your purposes, it'll mess with dates when they're six months in the past. In short, yes, it'll probably work for you in your limited testing. It will not be platform-independent (so no portability) and the behaviour of your parsing is not guaranteed given the range of 'legal' filenames on various systems. (Ext4, for example, allows spaces and newlines in filenames).

Having said all that, personally, I'd use ls because it's fast and easy ;)

Edit

As pointed out by Hugo in the comments, the OP doesn't want to use stat. In addition, I should point out that the below section is BSD-stat specific (the %Sm flag doesn't work when I test on Ubuntu; Linux has a stat command, if you're interested in it read the man page).

So, a non-stat solution: use date

date, at least on Linux, has a flag: -r, which according to the man page:

display the last modification time of FILE

So, the scripted solution would be similar to this:

date -r ${MY_FILE_VARIABLE}

which would return you something similar to this:

zsh% date -r MyFile.foo
Thu Feb 23 07:41:27 CST 2012

To address the OP's comment:

If possible with a configurable date format

date has a rather extensive set of time-format variables; read the man page for more information.

I'm not 100% sure how portable date is across all 'UNIX-like systems'. For BSD-based (such as OS X), this will not work; the -r flag for the BSD-date does something completely different. The question doesn't' specify exactly how portable a solution is required to be. For a BSD-based solution, see the below section ;)

A better solution, BSD systems (tested on OS X, using BSD-stat; GNU stat is slightly different but could be made to work in the same way).

Use stat. You can format the output of stat with the -f flag, and you can select to display only the file modification data (which, for this question, is nice).

For example, stat -f "%m%t%Sm %N" ./*:

1340738054  Jun 26 21:14:14 2012 ./build
1340738921  Jun 26 21:28:41 2012 ./build.xml
1340738140  Jun 26 21:15:40 2012 ./lib
1340657124  Jun 25 22:45:24 2012 ./tests

Where the first bit is the UNIX epoch time, the date is the file modification time, and the rest is the filename.

Breakdown of the example command

stat -f "%m%t%Sm %N" ./*

1. stat -f: call stat, and specify the format (-f).
2. %m: The UNIX epoch time.
3. %t: A tab seperator in the output.
4. %Sm: S says to display the output as a string, m says to use the file modification data.
5. %N: Display the name of the file in question.

A command in your script along the lines of the following:

stat -f "%Sm" ${FILE_VARIABLE}

will give you output such as:

Jun 26 21:28:41 2012

Read the man page for stat for further information; timestamp formatting is done by strftime.