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# 1  
Old 08-08-2013
Bash variable recursion
Not sure how to ask this question. I want concatenate strings and variable recursively into new variable. For example:
Code:
infile01=/dir/subfolder/file01.txt
infile02=/dir/subfolder/file02.txt
infile03=/dir/subfolder/file03.txt
for i in {01..03}
do
u=${"infile"$i}
echo $u
done

I got error message:
Code:
-bash: ${"infile"$i}: bad substitution

How do I get output?
Code:
/dir/subfolder/file01.txt
/dir/subfolder/file02.txt
/dir/subfolder/file03.txt

Thanks a lot!
# 2  
Old 08-08-2013
Whatever you are trying to do is a bad programming practice.

I would highly recommend using arrays instead which is pretty much straightforward:
Code:
infile[1]="/dir/subfolder/file01.txt"
infile[2]="/dir/subfolder/file02.txt"
infile[3]="/dir/subfolder/file03.txt"

for i in {1..3}
do
        echo "${infile[$i]}"
done

This User Gave Thanks to Yoda For This Post:
yifangt
# 3  
Old 08-08-2013
Or, I tried:
Code:
for i in {01..03}
do
u=$"infile"$i
echo $u
done

and got
Code:
infile01
infile02
infile03

but I was expecting
Code:
/dir/subfolder/file01.txt
/dir/subfolder/file02.txt
/dir/subfolder/file03.txt

---------- Post updated at 05:58 PM ---------- Previous update was at 05:55 PM ----------

Thanks Yoda!
I should have thought of that way.
# 4  
Old 08-08-2013
You can use eval to acheive it, but using it is a security risk and hence a bad programming practice.
Code:
infile01=/dir/subfolder/file01.txt
infile02=/dir/subfolder/file02.txt
infile03=/dir/subfolder/file03.txt
for i in {01..03}
do
        u=$( printf "infile%02d" "$i" )
        eval echo \$"$u"
done

# 5  
Old 08-08-2013
You need to use eval....here is a simple example
Code:
[root@localhost cgi-bin]# x1="foo"
[root@localhost cgi-bin]# n=1
[root@localhost cgi-bin]# eval echo \${x$n}
foo

This User Gave Thanks to blackrageous For This Post:
yifangt
# 6  
Old 08-08-2013
Quote:
Originally Posted by Yoda
You can use eval to acheive it, but using it is a security risk and hence a bad programming practice.
A little perspective is in order.

Would you pass untrusted data to find . -exec $untrusted_data \;? Or rm $untrusted_data?

Simply using eval is not a security risk nor is it bad practice.

Trusting untrustworthy data is the real problem and it is bad practice regardless of the tool involved.

Regards,
Alister
# 7  
Old 08-08-2013
Hi Yoda!
Another question not about the concatenation but related to the array index when it is "08". The problem is with 8 & 9 that caused problem as
Code:
 "bash: 08: value too great for base (error token is "08"). "

I am aware this is related to octal for 01~07 but not 08~09.. etc. I want this leading 0 for 1~9 for the filenames to be nicely aligned. What is the trick to include a leading zero to the number as array index, if any? Thanks a lot!
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