[SOLVED] bash won't search within a variable with a user imputed variable

hoisu · 04-01-2014, 08:00 PM

Hi Everybody ,

I hope i don't mess it up because this is my first post on a forum ,so please excuse me if I'm doing something wrong , so let's get into it .

So i have this bash script , in it I have these 2 variables :
ex :

a=($ls)
b=$1 - this will be a user input (example read -p "enter a variable: " b )

My question is : How can i search the for $b in $a (if i want to find for example the file named a )

I have already tried these options and didn't work :

if [[ ! "$b" =~ $a]] ; then

echo "The variable '${b}' does not exist "

exit 1
fi

and i tried whit grep like this :
grep -w -h ${b} ${a}

but no luck , if anyone can give me an idea how to go forward with this ,I would be very thankful .

thanks guys ,

NevemTeve · 04-01-2014, 11:22 PM

please insert your complete script between [code] and [/code] tags
please explain this line:

Code:

a=($ls)

please use this command in your script:

Code:

set -xv

grail · 04-02-2014, 02:37 AM

Yes it does feel like you have given only part of the script and that you may well have some typos, ie you didn't copy and paste but tried to type it by hand.

Based on what I sort of see, I would hazard a guess at the following:

1. 'a' is supposed to be an array comprised of the output of ls, if correct, the assignment should have been:

Code:

a=($(ls))

As a side note, if any of your files or directories have spaces in them, this will cause you all sort of headaches

2. You have given us 2 different options on how 'b' has been assigned:

Code:

# either the user passes the value to the script
b=$1

# or the user is requested for the information within the script and hence 'b' is assigned using read command
read -p "Enter a value for 'b': " b

Either can be used but not both as one will overwrite the other

Assuming all of the above is correct, the easiest solution is to use a for loop to iterate over the array and test each item against the value of 'b'

If I am way off, please explain further

hoisu · 04-02-2014, 06:11 AM

So this is the entire code :

Code:

echo "You have the following drives available : "

#I'm using curently cygdrive to check which disks i have mounted 


cd /cygdrive 
ls 


#reading the user input 

read -p "Enter the drive letter : " disk

#checking if drive letter was introduced 

if [[ ! $disk ]] ; then 

echo "You didn't introduce a drive letter   " 
 
exit 1 

fi 


#check if drive letter exists (with the ls command)

cd /cygdrive 
servers=($(ls))
#the problem was here , servers was declared as servers=$(ls) , but now i declared it as servers=($(ls)) and it works fine

if  [[ ! "${disk}" =~ ${servers}  ]]  ; then  

echo "Disk  '${disk}'  does not exist  " 


exit 1 
fi



echo "end of code " 

exit 0

@ grail thank you very much , I've found the problem , it seems that you were right !

Thanks everyone for the help!

sashi_hc · 04-02-2014, 07:28 AM

Why not simply use the -z option? This is one of the moost efficient way I can think of.

if [ -z $myvariable ]
then

fi

hoisu · 04-02-2014, 07:39 AM

Quote:

Originally Posted by sashi_hc

Why not simply use the -z option? This is one of the moost efficient way I can think of.

if [ -z $myvariable ]
then

fi

Because i needed to find a variable with another variable .

NevemTeve · 04-02-2014, 08:50 AM

it is sg like this:

Code:

if [ -d /cygdrive/"$disk" ]; then echo 'Found';
else echo 'Not found';
fi

grail · 04-02-2014, 09:23 AM

ummmm .... how does disk contain servers?? Shouldn't the servers, ie the array with multiple items in it, contain the disk?

Also, can you guarantee that all disks are unique and hence using a none enclosed regex will not potentially match other items?

I am going to go out on a limb here and say that if you explained what you actually need to do that someone may have a much better method as the current one seems terribly flawed.

KenJackson · 04-02-2014, 12:11 PM

Quote:

Originally Posted by hoisu

and i tried whit grep like this :
grep -w -h ${b} ${a}

but no luck

The syntax would be

Code:

echo "$a" | grep -w "$b"

That is, $a contains the content to be searched, not the name of a file to be searched. You can make grep work on that content by piping it to grep's stdin, which grep reads by default when no file is specified.