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Topic: Shell Scripting Doubts (Read 22 times) |
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Maximus Decimus
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Shell Scripting Doubts
« Thread started on: Jul 29th, 2004, 6:22pm » |
  
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I was fooling around with a shell script which reads as
Code:for FILE in $HOME/*.pls
do
cp $FILE ${HOME}/source
chmod a+r ${HOME}/source/${FILE}
done
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The idea is that all *.pls files in home dir are copied to a subdir ~pranand/source and then perms are for all to read.
But what's the deal with the { and } ? When does one use braces while referencing variables? Some rules of thumb please.
PS: The script doesnt work if the second line reads as follows: chmod a+r $HOME/source/$FILE
or
chmod a+r $HOME/source/${FILE}
but if the first line is cp $FILE $HOME/source
it works fine
I can figure out that if the stmt reads
chmod a+r $HOME/source/$FILE it wont work because FILE holds the absolute path which when appended to $HOME/source points to a non existent file.
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JediMaster
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Re: Shell Scripting Doubts
« Reply #1 on: Jul 29th, 2004, 9:54pm » |
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on Jul 29th, 2004, 6:22pm, Maximus Decimus wrote:But what's the deal with the { and } ? When does one use braces while referencing variables? Some rules of thumb please.
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The {} is used when there could be an ambiguity about how the shell can identify the variable. For example $NUMst can be refering to ${NUM}st (like in 1st if NUM=1) or NUMst variable.
Quote:PS: The script doesnt work if the second line reads as follows: chmod a+r $HOME/source/$FILE
or
chmod a+r $HOME/source/${FILE}
but if the first line is cp $FILE $HOME/source
it works fine
I can figure out that if the stmt reads
chmod a+r $HOME/source/$FILE it wont work because FILE holds the absolute path which when appended to $HOME/source points to a non existent file.
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$HOME/source/$FILE or ${HOME}/source/${FILE} will both expand to a wrong path and the script will not work in any case?? Is it working for you?
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