Newbie sh-posix question about While loop

[Jason Martens]

I have the following bit of code, but it generates an error every time I run it:


while [[ $I -lt $CNT ]];
do
if [[ `grep ${VOLUMES[$I]} *postBackup | grep "has been successfully removed" | wc -l` -eq 1 ]]
let SucessfullyMerged = $SucessfullyMerged + 1
echo ${VOLUMES[$I]}
let I=$I+1;
done


It generates this error message:
./BackupStatus[16]: Syntax error at line 23 : `done' is not expected.

In my script, line 23 is the line immediately after the done. I'm kind of new to this, can someone tell me what I'm doing wrong?

Thanks,
Jason

[MarkSyder · Accepted solution]

You have an "if" inside your do - done loop.

You need to end the if with a "fi" before the done.

Mark Syder (like the drink but spelt different)

[Joseph C. Denman]

problems with the "if" area.

if
then
else
fi


Hope this helps.

...jcd...

[A. Clay Stephenson]

Your if statement does not conform to this:
if [[ some_condition ]]
then
command1
command2
fi

Lose the semicolon in let I=$I + 1, if fact better syntax is is simply

((I += 1))

Learn to enclose ALL variables in {}.
Start using the typeset command to type variables so that instead of
I=0
do
typeset -i10 I=0

[Jason Martens]

Thanks all! That was it. Clay, can you explain this a bit more? Why is it better to use the typeset syntax? And why enclose variables in {}?

Learn to enclose ALL variables in {}.
Start using the typeset command to type variables so that instead of
I=0
do
typeset -i10 I=0

[A. Clay Stephenson]

One word: discipline. If you "zig" each and everytime, you no longer have to decide to "zig" or "zag". In all cases, the {}'s will work; in SOME cases they are required in order for the shell to correctly parse a statement. Do it every time and you can't go wrong.

The typeset is the preferred method nowadays. It gives the shell intepreter hints about how a given variable should be treated and what are legal operations to perform on it. Typesetting also avoids ambiguities and the radix (base) of a given integer variable which in turn avoids problems. For example, consider:

I=08

Now that might be an error if your intent was to create an octal number (or if you grabbed 08 out of a cal command) BUT if
you first did:

typeset -i10 I
then
I=08
or
I=8
would be correctly interpreted in either case.

Since you indicated that you were a newbie, learn the disciplined approach early and you won't need to unlearn less than well-disciplined habits.

[Dan Martin_1]

Jason,

I would also clean up your grep statement. Either:

if grep "${VOLUMES[$I]}.*has been successfully removed" *postBackup

or

cnt=$(grep -c "${VOLUMES[$I]}.*has been successfully removed" *postBackup)
if ((cnt == 1))

. . . depending on whether you need to check for any occurence of the line (first example) or just one occurence of the line (second example).

Notice the $() - this is the POSIX shell's command substitution syntax and is more robust than the back ticks.

Also, you do not need to use the "$" when using let or (( )). ((i = i + 1)) or ((i += 1)) or let "i += 1"

Dan