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https://github.com/johnsonjh/isnewer

isnewer: A utility to compare file modification dates; re-implementation of AT&T Research UNIX V8 newer(1)
https://github.com/johnsonjh/isnewer

compare date newer shell unix utility v8

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isnewer: A utility to compare file modification dates; re-implementation of AT&T Research UNIX V8 newer(1)

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README 

        



# isnewer - compare file modification dates



A free implementation of AT&T Research UNIX V8 `newer(1)`.



## Overview



* It is unfortunately difficult to portably and robustly determine the

  newer of two files from a UNIX shell script - the POSIX baseline

  [`test(1)`](https://pubs.opengroup.org/onlinepubs/9699919799/utilities/test.html)

  does not include the `-nt` and `-ot` operators commonly seen on GNU

  and BSD systems.  Efforts to update the POSIX specification to include

  these and other widely-implemented `test(1)` extensions appears to have

  [stalled](https://www.austingroupbugs.net/view.php?id=375).



* AT&T Research UNIX V8 (never released under a proper FLOSS license)

  from 1985 offers a reasonable precedent, having provided this

  functionality via the `newer(1)` shell utility:



  ```

    NAME

         newer - test file modification dates



    SYNOPSIS

         newer file1 file2



    DESCRIPTION

         Newer yields a zero return code if file1 exists and file2

         does not, or if file1 and file2 both exist and file1's

         modification time is at least as recent as that of file2.

         It yields a non-zero return code otherwise.

  ```



* `isnewer` intends to be compatible with the AT&T Research UNIX V8

  `newer(1)` implementation, with the addition of supporting the

  following command-line arguments:



  * `-v` or `--version` - Prints version information to standard error

  * `-h` or `--help`    - Prints usage information to standard error



* These new arguments are exclusive; that is, they may not combined

  with each other and may not be used in conjunction with any date

  comparisons.



* The name `isnewer` was chosen for this package to avoid clashing with

  other utilities of the same name that may be provided by operating

  systems (*i.e.* Research UNIX V8) or as components of other packages

  (*i.e.* some versions of teTeX).  Users, system administrators, and

  distribution packagers can make use of

  [`alternatives`](https://wiki.debian.org/DebianAlternatives) or a

  similar facility to provide more convenient access to this utility.



## Building



* `isnewer` should work on any POSIX-like system with a C compiler.

* A convenient `Makefile` for building and running tests is provided.



## Notes



* No effort is made to utilize sub-second mtime precision

* [mtime comparison considered harmful](https://apenwarr.ca/log/20181113)

  (according to some people)



## License



* `isnewer` is distributed under the terms and conditions of the

  following Zero-Clause BSD (*0BSD*) license.



  ```

  Copyright (c) 2022 Jeffrey H. Johnson 



  Permission to use, copy, modify, and/or distribute this software for

  any purpose with or without fee is hereby granted.



  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

  MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR

  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN

  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF

  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

  ```