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confusion in use of exit 0

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# 1  
Old 10-10-2012
Java confusion in use of exit 0


i am new to shell scripting.

i was going thru the part option and arguments. on this section i fail to understand the use of exit 0 in below example .
USAGE="Usage: $0 [-c|-t] [file|directory]"
case "$1" in
-t) TARGS="-tvf $2" ;;
-c) TARGS="-cvf $2.tar $2" ;;
*) echo "$USAGE"
exit 0
tar $TARGS

also, i got and when i use option c in the script. however directory created successful.

below command i use to create the dir .
./pmeter -c a3

and below is the error which i got
tar: a3: Cannot stat: No such file or directory
tar: Error exit delayed from previous errors.

but i can see dir is created .
$ ls -lrt a3.tar
-rw-r--r--  1 khare  guest  1024 Oct 10 03:08 a3.tar

# 2  
Old 10-10-2012
Hi Scriptor,

The file has to exist before you can run this.

IE the file a3 would have to exist to create a valid a3.tar.


# 3  
Old 10-10-2012
sorry but i am not able to understand you mention.
request you to please explain again .

once again sorry for the inconvenience
# 4  
Old 10-10-2012
Hi Scriptor,

If you run the script like this;

davem]:$ ./pmeter -c "filename"

Then "filename" should exist and will be archived to "filename.tar"


# 5  
Old 10-10-2012
one more thing
why i am getting error when trying to create a file.
$ ./pmeter -c "a5"
tar: a5: Cannot stat: No such file or directory
tar: Error exit delayed from previous errors.

---------- Post updated at 04:26 PM ---------- Previous update was at 03:14 PM ----------

waiting for response
# 6  
Old 10-10-2012
You have to be aware that your script is running some severe risks: create 2 or three files in a new empty directory (run "mkdir x ; cd x ; touch a; touch b; touch c") and then run

pmeter -c '*'

Do an "ls -l" before and after and notice what happens. I do hope you created a new directory for this - in this case just go one level up and remove it with "rm -rf x" instead of having to deal with "*.tar".

If you want to reduce the risk check your passed arguments before:

if [ \( ! -f "$2" \) -a \( ! -d "$2" \) ] ; then
     echo "Error: only (regular) files or dirs allowed." > /dev/stderr
     exit 1

The "-f" asks if the contents of "$2" exists and is a regular file, the "-d" if it is a directory, the "-o" is a logical AND, the "!" is a logical NOT.

I hope this helps.

# 7  
Old 10-10-2012
Hi Bakunin

thx for your response.
what i was able to understand from your response is that, i was getting below error because there was no such file or dir .

however this time i make a file keto and dir qq and then run the script.

below is the command for file keto
 $ ./pmeter -c keto

a keto

below is the command for dir qq
$ ./pmeter -c qq

a qq

Now my question is why i am getting a letter "a" in the output along with file or dir name .

i thing it should come back to the prompt.

-rw-r--r-- 1 khare guest 100 Oct 10 11:23 keto
-rw-r--r-- 1 khare guest 2048 Oct 10 11:23 keto.tar
drwxr-xr-x 2 khare guest 512 Oct 10 11:26 qq
-rw-r--r-- 1 khare guest 1536 Oct 10 11:26 qq.tar


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