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unix command - what happens under the hood


 
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# 1  
Old 08-27-2009
unix command - what happens under the hood

Hello everyone,

When I run the command: rm adkjad (assuming the file adkjad doesn't exist), I get the following message:

adkjad: No such file or directory

I want to run this command, but I want a succesful return code whether the file is there or not.

I tried: rm adkjad 2> /dev/null , redirecting stderr to never never land, but I still get some type of negative return code.

Is there some other output(I am unware of) that I can send to /dev/null also?

Thanks in advance.

Robert
# 2  
Old 08-27-2009
what do you mean by negative return code???
according to me you should get 2 as return code ($?)
# 3  
Old 08-27-2009
I actually issue this command from another piece of software(which sends the command to the unix server - and gets a success or fail response). Unfortunately, even redirecting stderr(rm adkjad 2> /dev/null), the software I am using still gets a return code of 2, causing it to stop processing. Not sure how to get a success response regardless if rm command is succesful or not.

thx
# 4  
Old 08-27-2009
I think by "negative" you mean not 0?

Sending something to standard error, or anywhere else doesn't change the return code of a command.

Code:
rm noSuchFile
 
rm:  cannot lstat `noSuchFile`: No such file or directory
 
echo $?
 
1

Code:
rm noSuchFile | bc
 
rm:  cannot lstat `noSuchFile`: No such file or directory
 
echo $?
 
0

(this command makes no sense, but it also doesn't return a "negative" return code - the result of bc is 0, and that's what's returned, not the result of rm, in this case)
# 5  
Old 08-27-2009
Or something like:

Code:
rm adkjad 2> /dev/null ||  echo " " >/dev/null

# 6  
Old 08-27-2009
Quote:
Originally Posted by scottn
Code:
rm noSuchFile | bc
 
rm:  cannot lstat `noSuchFile`: No such file or directory
 
echo $?
 
0

(this command makes no sense, but it also doesn't return a "negative" return code - the result of bc is 0, and that's what's returned, not the result of rm, in this case)
good idea!
a slight alternative:
Code:
rm noSuchFile 2>/dev/null| :

# 7  
Old 08-27-2009
Quote:
Originally Posted by robert4732
Hello everyone,

When I run the command: rm adkjad (assuming the file adkjad doesn't exist), I get the following message:

adkjad: No such file or directory

I want to run this command, but I want a succesful return code whether the file is there or not.

I tried: rm adkjad 2> /dev/null , redirecting stderr to never never land, but I still get some type of negative return code.

Is there some other output(I am unware of) that I can send to /dev/null also?

Thanks in advance.

Robert
I like to use "rm -f" - the -f is force the remove, best used in batch jobs.

If the file is there or not, it will be removed and return a "0" status code.

However, if for some reason, you cannot delete the file (wrong ownership of the directory), it will return a bad code.
 

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