if ! tar cf "${DIR}".tar "${DIR}"
then mail -s "tar failed $DIR" $MailAddress <<< "creating of tar $DIR failed due to error, removing $DIR.tar"
rm -f "$DIR".tar
continue
fi
if ! tar cf "${DIR}".tar "${DIR}"
then mail -s "tar failed $DIR" $MailAddress <<< "creating of tar $DIR failed due to error, removing $DIR.tar"
rm -f "$DIR".tar
continue
fi
We realize that the tab key is broken on your keyboard and you don't care about being able to see the structure of your code by properly indenting it. So, yes, the above code will be accepted by your shell.
But, some day, perhaps years from now when you have to look at your code again when something needs to be changed, you'll realize that programming style does make a difference and if statements should be indented when they appear inside a loop and statements in then and else clauses in if statements should be indented further.
Code:
if ! tar cf "${DIR}".tar "${DIR}"
then mail -s "tar failed $DIR" $MailAddress <<< "creating of tar $DIR failed due to error, removing $DIR.tar"
rm -f "$DIR".tar
continue
fi
ok so the ! (explanation mark) means if the command doesnt return a 0 or if it fails
sorry to bang on about this just learning so excuse me if i am annoying you guys
---------- Post updated at 08:43 AM ---------- Previous update was at 07:39 AM ----------
also i want to add to my script that if the directory stays the same size then it is safe to start of the script but if the directory changes size ie someones is still moving the directory in "to_be_archived" dont do it and wait till the directoey doesnt increase in size and then it can start off the script
Last edited by robertkwild; 04-25-2016 at 11:11 AM..
so the ! means if its not equal to 0/doesnt succeed/fails in doing the tar command it will send a mail and remove the tar file?
Yes. Whenever the tar-command returns a non-zero value the part between "then" and "fi" (or, in case an else-branch is there, the "then and the "else") is executed. In your case, since there is a "mail"-command and an "rm"-command it will do exactly that.
Quote:
Originally Posted by robertkwild
sorry to bang on about this just learning so excuse me if i am annoying you guys
You are not annoying us because of your questions. What is really annoying is the way you constantly ignore what we say about indenting. Believe me, i have written several hundred thousands lines of code in my life (and Don, i believe, something in the same order of magnitude) and i can tell you that it is absolutely necessary! I wrote programs in Assembler, C, FORTRAN, Clipper, and some interpreted languages (mostly shells) and this was constant in all of them!
If you do not understand how to indent properly: say so. We will explain it to you. But to simply ignore our many suggestions, THAT is really annoying - because it creates a feeling that what we do is in vain.
Here is a simple procedure how to indent properly (in every language):
Indentation is for making stand out two sorts of statements: conditionally executed ones and loop contents. Here is how a loop should look like:
Code:
loop-command (while, for, until, repeat, ....)
command to execute every iteration of the loop 1
command to execute every iteration of the loop 2
command to execute every iteration of the loop 3
[...]
end-loop command
What you see instantly is: 1) where the loop starts and 2) where it ends and 3) what it consists of (the "loops body").
Here is a real-world example in shell:
Code:
(( i = 1 ))
while [ $i -le 100 ] ; do
echo "i is now: $1"
(( i = i + 1 ))
done
Now, this is my style of doing it, Don Cragun does it a bit different (but equally correct - that is a matter of personal taste):
Code:
(( i = 1 ))
while [ $i -le 100 ]
do
echo "i is now: $1"
(( i = i + 1 ))
done
Now the conditionals: the same principle applies. Whatever is causing the condition (the "if"-part) is put into a line, then everything between that and the else-line is indented, the "else" itself is at the same level as the "if" and then everything else is indented again until the end of the "if":
Code:
if <some-condition>
command executed if condition is true 1
command executed if condition is true 2
command executed if condition is true 3
[...]
else
command executed if condition is false 1
command executed if condition is false 2
command executed if condition is false 3
[...]
end-if
Here is a real-world example, this time not in shell but in C:
Code:
if (a < b ) {
printf( "a is smaller than b\n" );
a += 1;
} else {
printf( "a is NOT smaller than b\n" );
b += 1;
}
Notice again how the important parts - which condition everything is based upon ("a < b"), which part is executed when and where each part begins and ends - stand out.
Most programming languages allow to "chain" if-statements. Altough it is not necessary i always align the various conditions horizontally so that they start at the same column. I find that easier to keep track of:
Code:
if [ $x -eq 1 ] ; then
echo "x is 1"
elif [ $x -eq 2 ] ; then
echo "x is 2"
else
echo "x is neither 1 nor 2"
fi
Finally there is another conditional in most programming languages: "case" (or, in C, "switch"). It allows for several branches depending on various values of a single variable or expression. The syntax differs from language to language, but the sctructure is always the same:
Code:
case <expression>
first-possible-value)
command 1 to execute if expression is "first-possible-value"
command 2 to execute if expression is "first-possible-value"
command 3 to execute if expression is "first-possible-value"
[...]
second-possible-value)
command 1 to execute if expression is "second-possible-value"
command 2 to execute if expression is "second-possible-value"
command 3 to execute if expression is "second-possible-value"
[...]
third-possible-value)
[...]
end-of-case
Here is the chained if-else-construct from above, this time with a "case":
Code:
case $x in
1)
echo "x has the value 1"
;;
2)
echo "x has the value 2"
;;
*)
echo "x has neither the value 1 nor 2"
;;
esac
Notice how the important parts spring right into your eyes: the beginning and end of the construct, the various possible values (1, 2, *) and what part of the code is to be executed if these were to be the case (again, with the beginning and the ending of each).
Finally: you define some "indenting step" for yourself. Pick anything you are comfortable with. I prefer 5 spaces because i like the clear picture it gives. On the other hand you start pretty soon to get far right if you have many indentation steps. Some prefer only 3 spaces, some even two. One can nest more levels with less indentation but at the same time different parts of the code are not separated as clearly as with more indentation. Find your own optimum but FIND one. Do NOT write code the way you do because you will hate yourself once you have to correct or change your own programs after a while.
I hope this helps.
bakunin
These 3 Users Gave Thanks to bakunin For This Post:
ok so the ! (explanation mark) means if the command doesnt return a 0 or if it fails
sorry to bang on about this just learning so excuse me if i am annoying you guys
---------- Post updated at 08:43 AM ---------- Previous update was at 07:39 AM ----------
also i want to add to my script that if the directory stays the same size then it is safe to start of the script but if the directory changes size i.e. someones is still moving the directory in "to_be_archived" dont do it and wait till the directoey doesnt increase in size and then it can start off the script
It isn't that you're annoying us. We know you're learning. As bakunin said, what bothers us is that you ask questions, we make suggestions, and you ignore our suggestions. (Did you try the script I suggested in post #16 in this thread to see what it would do? Did you even read that post?)
The size of a directory tells you very little about whether or not files in that directory are growing, and (if any files have ever been removed from a directory) even if a new file is created in a directory, its size might not change.
It would be much better if you would create a hidden directory under /to_be_archived (such as /to_be_archived/.in_progress/project), move everything into that directory, and then after that project directory contains everything you want to archive, issue the command:
which will be an atomic operation. Your existing script won't see the hidden directory so it won't see .in_progress/project until it is ready to process after it has been moved up.
Last edited by Don Cragun; 04-25-2016 at 07:47 PM..
My take is that directory space is allocated not just one entry at a time, but by blocks. So that there may be no noticeable change when objects are added to a directory.
Similarly, on some systems (perhaps older), directory space was not reduced when object are deleted.
So trying to detect a change in directory content by monitoring the size seems to be fruitless.
However, there are, as can be seen from the responses at LQ, that there may be ways to monitor events within a directory. (I thought I had posted a demonstration of that, but I cannot find it just now.)
Best wishes ... cheers, drl
---------- Post updated at 06:17 ---------- Previous update was at 06:08 ----------
Hi.
Quote:
Originally Posted by bakunin
Finally: you define some "indenting step" for yourself. Pick anything you are comfortable with. I prefer 5 spaces because i like the clear picture it gives. On the other hand you start pretty soon to get far right if you have many indentation steps. Some prefer only 3 spaces, some even two. One can nest more levels with less indentation but at the same time different parts of the code are not separated as clearly as with more indentation. Find your own optimum but FIND one. Do NOT write code the way you do because you will hate yourself once you have to correct or change your own programs after a while.
Exactly.
In my situation, I almost never format/indent manually because I'm too fallible and there are tools to do this. I apply these continually while I am developing. Here are some:
dont believe it, on the last hurdle i get this error while running my script
bash: /archive_script.sh: /bin/bash^M: bad interpreter: No such file or directory
this is my code
Code:
#!/bin/bash
cd /to_be_archived/
for DIR in * ;
do
MailAddress="robertw@molinare.co.uk"
if ! inotifywait -rq -e modify,create,delete -t 60 /to_be_archived/"$DIR" ; then
mail -s "Modified $DIR" $MailAddress <<< "$DIR failed has been modified within the last minute"
continue
fi
if ! tar cf "$DIR".tar "$DIR" ; then
mail -s "tar failed $DIR" $MailAddress <<< "creating of tar $DIR failed due to error, removing $DIR.tar"
rm -f "$DIR".tar
continue
fi
if [ -f /archived_projects/"$DIR".tar ]; then
mail -s "duplicate exists $DIR" $MailAddress <<< "$DIR.tar already exists"
rm -f "$DIR".tar
continue
fi
if ! rsync -a "$DIR".tar /archived_projects/ ; then
mail -s "rsync failed $DIR" $MailAddress <<< "rsync of $DIR failed due to error, removing $DIR.tar"
rm -f "$DIR".tar
continue
fi
if ! rm -f "$DIR".tar ; then
mail -s "remove tar failed $DIR" $MailAddress <<< "removing of tar $DIR failed due to error"
continue
fi
if ! rm -rf "$DIR" ; then
mail -s "remove folder failed $DIR" $MailAddress <<< "removing of $DIR failed due to error"
continue
else
mail -s "success $DIR" $MailAddress <<< "successfully completed archiving $DIR"
fi
done
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04-25-2016
