Puppy Linux Discussion Forum

[snayak]

Dear All,

After trying to take backup of modified files only(http://www.murga-linux.com/puppy/viewtopic.php?t=82975), I came up with two small scripts. Here I am sharing the scripts, please use it if you find it good. Please suggest improvements.

This script automatically remembers upto what date you have taken the backup.

Now it will start taking your backup since 01 Jan 2013. Then it remembers the date on which you have taken the backup. Then onwards simply run this script, it will take backup of files modified since last backup!


backup.sh

[Bruce B]

Do you have all the necessary escape provisions? This is particularly important when distributing the scripts. We should presume the user doesn't understand the innards of the script.

src_dir=$1

Example: if $1 is innacurate or not entered what happens?

I do like this.

[ ! $1 ] && echo missing argument && exit
src_dir=$1
[ ! -d $src_dir ] && echo directory $src_dir doesn\'t exist && exit

[snayak]

Dear Bruce,

Many thanks for your suggestion. I got your point.
I thought,

cd $src_dir

shall fail in case src_dir is something wrong and the user shall be able to see the error message. I have everywhere provided echo to display whatever is going inside script.

Seeing your comments, to gain a bit more knowledge, I checked these two pages for understanding "[ expression ]".

1. http://en.wikibooks.org/wiki/Bash_Shell_Scripting#Combining_conditions

2. http://www.gnu.org/software/bash/manual/bashref.html#Bash-Conditional-Expressions

What is the difference between "[ expression ]" and "[[ expression ]]" ?

In link2, the first line reads "Conditional expressions are used by the [[ compound command and the test and [ builtin commands." What does it mean?

Sincerely,
Srinivas Nayak

[snayak]

Scripts updated to automatically remember the last backup date and time. So next time when you run this script, it will take backup of files modified since last backup!

[snayak]

Script updated to use absolute path of its own.

Learnings:
1. 'realpath' command shows the absolute path of a file.
2. When a script is in /bin, and the script is executed, $0 holds its full path, like '/bin/a.sh'

[snayak]

backup script modified to backup files downloaded since last backup.

Learning:

"find /mnt/sda5 -cnewer /tmp/b.txt" searches all files whose "inode information changed" since the "last modification time" of /tmp/b.txt.

[heenry]

I'm wondering about the escape provisions also as this is a fundamental part of scriipt distribution.