set a variable with a variable name - Page 2

chebarbudo · #1 (**permalink**) 3 Weeks Ago

Ooops, in my real script, I'm not using the file as it is but I grep it first.
What's the correct syntax to use then?

Code:

r29829:~# cat conf
# comment
A=1
B=2
# C is set to three
C=3
r29829:~# cat testconf.sh
#!/bin/bash
while IFS="=" read lvalue rvalue; do
        eval $lvalue=$rvalue
done < grep -v '^#' conf
echo "-$A-$B-$C-"
r29829:~# ./testconf.sh
./testconf.sh: line 4: syntax error near unexpected token `-v'
./testconf.sh: line 4: `done < grep -v '^#' conf'

Scrutinizer · #2 (**permalink**) 3 Weeks Ago

Hi Chebarbudo,
in bash (and only in bash) the correct syntax would be:

Code:

#!/bin/bash
while IFS="=" read lvalue rvalue; do
        eval $lvalue=$rvalue
done < <(grep -v '^#' conf)
echo "-$A-$B-$C-"

An alternative that also works in other shells would be:

Code:

grep -v '^#' conf|
{ while IFS="=" read lvalue rvalue; do
        eval $lvalue=$rvalue
  done
  echo "-$A-$B-$C-"
}

chebarbudo · #3 (**permalink**) 3 Weeks Ago

Hi Scrutinizer,

Thanks for your help, the bash syntax works fine.
Although do you know where I can find documentation for this type of redirection? So far I only knew the following:
|
>
>>
<
<<
<<<

Santiago

Scrutinizer · #4 (**permalink**) 3 Weeks Ago

Hi Santiago,

The redirection is a simple < together with process substitution

S.

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