CT320 HW5: File Tracker

Motivation

Files appear and disappear. It’s all so hard to follow. If only there were a program to help you keep track of things!                 

Summary

For this assignment, you will write a program called “track”, which helps you keep track of things. It can be a bash script, a perl script, or a python3 script, but nothing else. This program is useful for system monitoring. It will tell you about any files underneath your home directory that have appeared or vanished since the last time this program executed.                 

Output

Normal track output goes to standard output. Only write to standard error for errors.                 

track would typically be executed from cron, where the output gets mailed to you. Of course, track itself knows nothing about email—track simply produces output or not. cron handles emailing the output to you.                 

Sample Runs

Here are some sample runs ($ is my prompt):                 

$ cd
$ ./track
$ touch ~/tmp/alpha
$ date >~/tmp/beta
$ sleep 60
$ cd src
$ echo "Hello" >>gamma
$ ~/track
New:
    -rw------- 1 ct320 class  6 Oct 16 15:13 src/gamma
    -rw------- 1 ct320 class  0 Oct 16 15:12 tmp/alpha
    -rw------- 1 ct320 class 29 Oct 16 15:12 tmp/beta
$ rm ~/tmp/beta
$ cp /etc/group ~/vote-for-jack-in-the-year-65535
$ ~/track
Deleted:
    tmp/beta
New:
    -rw------- 1 ct320 class 1021 Oct 16 15:13 vote-for-jack-in-the-year-65535
$ rm ~/tmp/alpha ~/vote-for-jack-in-the-year-65535
$ ~/track
Deleted:
    tmp/alpha
    vote-for-jack-in-the-year-65535
$ ~/track
$

~/.track-info

• If ~/.track-info does not exist, that means that this is the first run, so be silent.
• Otherwise, use ~/.track-info to keep track of what’s there.

    export STACK_FRAME_LINK_OVERRIDE=ffff-ad921d60486366258809553a3db49a4a

Hints

• Don’t track file data; just remember of which files exist.
• This script must work for any user, no matter what their username is, no matter what the path of their home directory is, and no matter what their current directory is.
• Show changes since the previous run; do not show all changes since the first run.

Requirements

• Produce a message to standard error, including the name of the file containing the script, upon any unexpected error, including:
  • can’t read or write ~/.track-info.
  • any arguments are given
  • can’t access a directory (the message must name the directory)
• Produce no output the first time track is executed.
• Only report files that have been created or removed—not those that have merely had their data modified.
• If file alpha gets renamed to beta, that’s the same as deleting alpha and creating beta.
• If either section (deleted or new files) is empty, then nothing is printed for that section, not even a header line.
• Within a section, the files must be presented in sorted order by path.
• Display results for plain files only—ignore directories, symlinks, etc.
• Ignore any plain file whose name begins with a dot. For example:
  • ignore foo/42/.zip
  • do not ignore .glorp/177777 or iota/.ajbaxah/bozo.
• Clean up any temporary files that you create.
• If you need to store data between runs, put it in ~/.track-info, which may be a file or a directory. Your program must create ~/.track-info, as needed. We won’t create it for you.
• Your output should be exactly the same as the output shown above, if you were to modify those files at that time.
  • Spaces matter (there are four leading spaces in the ls-like output).
    • Even indentation.
• Did you notice how the filenames in a given section all lined up, even when they had different sizes? That’s no accident.

Submission

Use web checkin, or:                 

    ~ct320/bin/checkin HW5 track

How to receive negative points: