Solved

use a variable (like $i) as part of another variables name in bash

Posted on 2013-06-20
5
234 Views
Last Modified: 2013-06-23
I have a file with variables like this...
server_1=
port_1=
user_1=

server_2=
port_2=
user_2=

Open in new window


I am trying to write a script that can read them in and manipulate them and write them back out.  And it should be able to handle any number of them.  Below is a simplified version of what I want to be able to do.  (i.e. not actually trying to edit anything here.  Just write it back out)

Is this at all possible?


source filewithvariables
for (( i=1; i<=$number_of_servers; i++ ))
do

echo "server_${i}=${server_${i}}" >> output 
echo "port_${i}=${port_${i}}" >> output 
echo "user_${i}=${user_${i}}" >> output 

done

Open in new window

0
Comment
Question by:Xetroximyn
  • 3
  • 2
5 Comments
 
LVL 84

Accepted Solution

by:
ozo earned 500 total points
ID: 39263887
eval echo "server_${i}=\${server_${i}}" >> output
or
name=server_${i}; echo "server_${i}=${!name}" >> output
0
 
LVL 84

Expert Comment

by:ozo
ID: 39263920
or
for name in ${!server_*}  ; do  echo "$name=${!name}"  ; done
0
 

Author Comment

by:Xetroximyn
ID: 39266692
Thanks!

Just want to understand this a bit better... I think I understand the val method.  Baiscally eval replaces the ${i} with the "1" and leaves the first $ in there because it's escaped and thus bash is left to execute
server_1=${server_1}

And I think I understand the indirect referencing with the ${!name} syntax.  It seems like it takes the contents of $name and uses that for the variable name to get the contents of instead of just getting the contents of ${!name}

However - if it worked like I think it does - I don't quite understand why these two things would not be the same

echo $name_1
i=1
echo $name_${!i}

Open in new window


any chance you can help me understand that?
0
 
LVL 84

Expert Comment

by:ozo
ID: 39267231
i=1
echo $name_${!i}
would have the same effect as
echo $name_$1
0
 

Author Closing Comment

by:Xetroximyn
ID: 39269814
TY!
0

Featured Post

Master Your Team's Linux and Cloud Stack

Come see why top tech companies like Mailchimp and Media Temple use Linux Academy to build their employee training programs.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
AD Cleanup by EmployeeID 11 45
exchange ,script 10 41
How to remove mailbox permission and export result with PowerShell in Exchange 2010. 4 44
ftp to port 21 4 41
Setting up Secure Ubuntu server on VMware 1.      Insert the Ubuntu Server distribution CD or attach the ISO of the CD which is in the “Datastore”. Note that it is important to install the x64 edition on servers, not the X86 editions. 2.      Power on th…
This article is meant to give a basic understanding of how to use R Sweave as a way to merge LaTeX and R code seamlessly into one presentable document.
The viewer will learn how to look for a specific file type in a local or remote server directory using PHP.
In this seventh video of the Xpdf series, we discuss and demonstrate the PDFfonts utility, which lists all the fonts used in a PDF file. It does this via a command line interface, making it suitable for use in programs, scripts, batch files — any pl…

785 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question