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while condition error:

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# 8  
Old 04-13-2012
Hi again

when i try to use this command, it works perfect:


Code:
while [ "$(fdisk -l /dev/disk/by-path/*usb* | wc -w)" -ne 0 ]

but when i try to use this command in while loop i get nothing


Code:
while [ "$(grep -vxFf ud uc > ed | wc -w)" -ne 0 ]

actually wc -w gives 0 even when there is couple of words in ed file. kindly comment why there is difference of working.
Moderator's Comments:
Mod Comment Code tags, PLEASE!
Last edited by Corona688; 04-13-2012 at 07:27 PM..
# 9  
Old 04-13-2012
Typing 'code:' is not the same thing as putting them in code tags. If you don't understand how, please observe this video:



Thank you.
# 10  
Old 04-13-2012
I don't understand the purpose of your code, and posting code which doesn't do what you want will never explain what you do want. Please explain your intention, not just the way you're trying to do it.

Why are you taking the number of words? What is that indicating?
# 11  
Old 04-13-2012
Quote:
while [ "$(fdisk -l /dev/disk/by-path/*usb* | wc -w)" -ne 0 ]
but when i try to use this command in while loop i get nothing

while [ "$(grep -vxFf ud uc > ed | wc -w)" -ne 0 ]
The > in the second command redirects the output of your weird grep command (not tested but what are ud and uc?) to a disc file called ed. Thus there is nothing left on the pipeline for wc to count. If the script ran without error, look for a file called ed in the current working directory.
The > in this context has does not mean greater-than.
# 12  
Old 04-14-2012
@methyl. yes you got it right. it is counting words in file ed. and grep command is sending difference of files ud and uc to ed. if there is any difference found then it will do some operataion. but in this case wc -w is giving output zero even when there are 2,3 lines in ed file. hope it clears my requirement.
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