Re: need bash variable syntax help
On 06/06/2014 08:52 PM, ToddAndMargo wrote:
Hi All,
In Bash script language, how do I create a variable name
from a variable?
I am trying to create a variable called abcStatus
x=abc
$xStatus=xyz
obviously doesn't work. What am I doing wrong?
Many thanks,
-T
Hi All,
For an eval free version:
x=z
a=x
echo ${!a}
z
-T
Re: need bash variable syntax help
On Fri, Jun 6, 2014 at 11:52 PM, ToddAndMargo toddandma...@zoho.com wrote: Hi All, In Bash script language, how do I create a variable name from a variable? I am trying to create a variable called abcStatus x=abc $xStatus=xyz obviously doesn't work. What am I doing wrong? Many thanks, -T It's not really core to Scientific Linux itself, but: For most bash cases where I've found myself wanting something like this, I've usually wound up using hashes instead. The first hash, abc, contains a list of variable names, abcstatus, abctime, abcdate, abcowner, etc. that can then be referrenced to refer to other valures or hashes as needed.
Re: need bash variable syntax help
On 6/7/2014 11:25 AM, Nico Kadel-Garcia wrote: On Fri, Jun 6, 2014 at 11:52 PM, ToddAndMargotoddandma...@zoho.com wrote: Hi All, In Bash script language, how do I create a variable name from a variable? I am trying to create a variable called abcStatus x=abc $xStatus=xyz obviously doesn't work. What am I doing wrong? Many thanks, -T It's not really core to Scientific Linux itself, but: For most bash cases where I've found myself wanting something like this, I've usually wound up using hashes instead. The first hash, abc, contains a list of variable names, abcstatus, abctime, abcdate, abcowner, etc. that can then be referrenced to refer to other valures or hashes as needed. I agree with everything said so far, but would like to toss in a chapter from the Advanced Bash-Scripting Guide (ABS). The dangers are of course still present, but might give a bit better explanation about what is going on. I actually do have scripts I use that utilize the \$$var method. http://www.tldp.org/LDP/abs/html/ivr.html
need bash variable syntax help
Hi All, In Bash script language, how do I create a variable name from a variable? I am trying to create a variable called abcStatus x=abc $xStatus=xyz obviously doesn't work. What am I doing wrong? Many thanks, -T
Re: need bash variable syntax help
There is probably a better way, (bash declare perhaps?), but: x=abc eval $(echo $x)Status=This works! Brandon Vincent On Sat, Jun 7, 2014 at 3:52 AM, ToddAndMargo toddandma...@zoho.com wrote: Hi All, In Bash script language, how do I create a variable name from a variable? I am trying to create a variable called abcStatus x=abc $xStatus=xyz obviously doesn't work. What am I doing wrong? Many thanks, -T
Re: need bash variable syntax help
On Fri, Jun 6, 2014 at 8:52 PM, ToddAndMargo toddandma...@zoho.com
mailto:toddandma...@zoho.com wrote:
Hi All,
In Bash script language, how do I create a variable name
from a variable?
I am trying to create a variable called abcStatus
x=abc
$xStatus=xyz
obviously doesn't work. What am I doing wrong?
Many thanks,
-T
On 06/06/2014 09:09 PM, Patrick J. LoPresti wrote:
x=abc
eval ${x}Status=xyz
echo $abcStatus
- Pat
Hi Pat,
Wow. I would have never figured that out on my own.
Thank you!
Follow on question: this works, but I would like
to clean it up:
xx=ech
eval $xxo abc
abc
-T
--
~~
Computers are like air conditioners.
They malfunction when you open windows
~~
Re: need bash variable syntax help
On Sat, Jun 7, 2014 at 3:52 AM, ToddAndMargo toddandma...@zoho.com wrote: Hi All, In Bash script language, how do I create a variable name from a variable? I am trying to create a variable called abcStatus x=abc $xStatus=xyz obviously doesn't work. What am I doing wrong? Many thanks, -T On 06/06/2014 09:14 PM, Brandon Vincent wrote: There is probably a better way, (bash declare perhaps?), but: x=abc eval $(echo $x)Status=This works! Brandon Vincent Hi Brandon, I completely blanked on eval. Thank you! -T -- ~~ Computers are like air conditioners. They malfunction when you open windows ~~
Re: need bash variable syntax help
Actually, it would be good if someone with a good deal of bash scripting experience chimed in. eval is not safe to use in a bash script. If the input is crafted cleverly, the script can execute unwanted commands. Not to mention the above examples don't work great with characters like ! which are evaluated as the built-in history command by eval. You need to actually escape my example with backslashes for that reason. Brandon Vincent On Sat, Jun 7, 2014 at 4:25 AM, ToddAndMargo toddandma...@zoho.com wrote: On Sat, Jun 7, 2014 at 3:52 AM, ToddAndMargo toddandma...@zoho.com wrote: Hi All, In Bash script language, how do I create a variable name from a variable? I am trying to create a variable called abcStatus x=abc $xStatus=xyz obviously doesn't work. What am I doing wrong? Many thanks, -T On 06/06/2014 09:14 PM, Brandon Vincent wrote: There is probably a better way, (bash declare perhaps?), but: x=abc eval $(echo $x)Status=This works! Brandon Vincent Hi Brandon, I completely blanked on eval. Thank you! -T -- ~~ Computers are like air conditioners. They malfunction when you open windows ~~
Re: need bash variable syntax help
On 06/06/2014 09:23 PM, ToddAndMargo wrote:
On Fri, Jun 6, 2014 at 8:52 PM, ToddAndMargo toddandma...@zoho.com
mailto:toddandma...@zoho.com wrote:
Hi All,
In Bash script language, how do I create a variable name
from a variable?
I am trying to create a variable called abcStatus
x=abc
$xStatus=xyz
obviously doesn't work. What am I doing wrong?
Many thanks,
-T
On 06/06/2014 09:09 PM, Patrick J. LoPresti wrote:
x=abc
eval ${x}Status=xyz
echo $abcStatus
- Pat
Hi Pat,
Wow. I would have never figured that out on my own.
Thank you!
Follow on question: this works, but I would like
to clean it up:
xx=ech
eval $xxo abc
abc
-T
How do I echo the variable?
echo $(eval ${x}Status)
isn't working
--
~~
Computers are like air conditioners.
They malfunction when you open windows
~~
Re: need bash variable syntax help
eval variable=${x}Status
echo ${!variable}
Brandon Vincent
Re: need bash variable syntax help
I think this is probably an X-Y problem.
http://mywiki.wooledge.org/XyProblem
Something missing is a description what the OP is trying to accomplish.
At least in shell scripts, every time I've thought I needed to declare a
variable name dynamically it turned out I was missing a better solution
somewhere. (In the case of metaprogramming I've never found Bash to be the
right tool.)
On Saturday 07 June 2014 04:41:14 Brandon Vincent wrote:
eval variable=${x}Status
echo ${!variable}
Brandon Vincent
Re: need bash variable syntax help
As zxq9 mentioned, there is probably a better way to do this. Honestly, the examples with eval should not be used. Here is the article I was looking for: http://mywiki.wooledge.org/BashFAQ/048 Brandon Vincent
