LinuxQuestions.org - [SOLVED] question about bash command

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question about bash command

I have to questions about this function I found on a script

Code:

function FILESIZE ( )

{

FN=${1:-/dev/null}

if [[ -e $FN ]]

then

# FZ=$(ls -s $FN | cut -d ' ' -f 1)

set -- $(ls -s "$FN")

FZ=$1

fi

}

first:

Code:

FN=${1:-/dev/null}

does this means initialize FN to the value of $1 and if $1 is not pass then set FN TO /dev/null?
second:

Code:

set -- $(ls -s "$FN")

the set command is a bit tricky here what is set being used for and what -- means in this case? I googled it, but the explanation I found was of no help

No, it means that set FN to $1 and if $1 isn't passed then set FN TO /dev/null

You can get file size using

Code:

stat -c '%s' file

Quote:

Originally Posted by custangro (Post 5138864)

No, it means that set FN to $1 and if $1 isn't passed then set FN TO /dev/null

what's the difference from what I said?

Yes you were correct on the first point (and yes I see no difference with yours and first reply)

As to the set command, there are actually 2 questions:

1. What does -- do? Answer, for some commands, set being one, -- means that anything received after this will be an argument to the set command. This means that if after -- you should receive something like '-a', which may normally be an a switch for set, that it should now be treated as an argument, example:

Code:

$ set -- -a

$ echo "$1"

-a

2. What is set being used for? Answer, the output from the command (ls -s "$FN"), will undergo word splitting based on IFS and each piece returned will be assigned to a parameter, ie the first piece will be $1. This would seem to be poor code because should any of the files referenced have spaces in them you will have unusual results for parameters, example:

Code:

$ touch 'this is my file'

$ ls

this is my file

$ ls -s

total 0

0 this is my file

$ for f

>do

>    echo "$f"

>done

0

this

is

my

file

As you can see this is not showing the expected output.