I have a script like that
genhash --use-ssl -s $IP -p 443 --url $URL | grep MD5 | grep -c $MD5
I want to get stream generated by genhash in a variable. How do I redirect it into a variable $hash
to compare inside a conditional?
if [ $hash -ne 0 ]
then echo KO
exit 0
else echo -n OK
exit 0
fi
I got error sometimes when using $(`code`)
constructor.
Finally i got some approach to that here: https://stackoverflow.com/a/7902174/2480481
Basically, using Tee to read again the ouput and putting it into a variable. Theres how you see the normal output then read it from the ouput.
is not? I guess your current task genhash will output just that, a single string hash so might work for you.
Im so neewbie and still looking for full output & save into 1 command. Regards.
read hash < <(genhash --use-ssl -s $IP -p 443 --url $URL | grep MD5 | grep -c $MD5)
This technique uses Bash's "process substitution" not to be confused with "command substitution".
Here are a few good references:
I guess compatible way:
hash=`genhash --use-ssl -s $IP -p 443 --url $URL | grep MD5 | grep -c $MD5`
but I prefer
hash="$(genhash --use-ssl -s $IP -p 443 --url $URL | grep MD5 | grep -c $MD5)"
Create a function calling it as the command you want to invoke. In this case, I need to use the ruok command.
Then, call the function and assign its result into a variable. In this case, I am assigning the result to the variable health.
function ruok {
echo ruok | nc *ip* 2181
}
health=echo ruok *ip*
If a pipeline is too complicated to wrap in $(...)
, consider writing a function. Any local variables available at the time of definition will be accessible.
function getHash {
genhash --use-ssl -s $IP -p 443 --url $URL | grep MD5 | grep -c $MD5
}
hash=$(getHash)
http://www.gnu.org/software/bash/manual/bashref.html#Shell-Functions
TL;DR
To store "abc"
into $foo
:
echo "abc" | read foo
But, because pipes create forks, you have to use $foo
before the pipe ends, so...
echo "abc" | ( read foo; date +"I received $foo on %D"; )
Sure, all these other answers show ways to not do what the OP asked, but that really screws up the rest of us who searched for the OP's question.
read
command.# I would usually do this on one line, but for readability...
series | of | commands \
| \
(
read string;
mystic_command --opt "$string" /path/to/file
) \
| \
handle_mystified_file
Let's pretend that the series | of | commands
is a very complicated series of piped commands.
mystic_command
can accept the content of a file as stdin in lieu of a file path, but not the --opt
arg therefore it must come in as a variable. The command outputs the modified content and would commonly be redirected into a file or piped to another command. (E.g. sed
, awk
, perl
, etc.)
read
takes stdin and places it into the variable $string
Putting the read
and the mystic_command
into a "sub shell" via parenthesis is not necessary but makes it flow like a continuous pipe as if the 2 commands where in a separate script file.
There is always an alternative, and in this case the alternative is ugly and unreadable compared to my example above.
# my example above as a oneliner
series | of | commands | (read string; mystic_command --opt "$string" /path/to/file) | handle_mystified_file
# ugly and unreadable alternative
mystic_command --opt "$(series | of | commands)" /path/to/file | handle_mystified_file
My way is entirely chronological and logical. The alternative starts with the 4th command and shoves commands 1, 2, and 3 into command substitution.
I have a real world example of this in this script but I didn't use it as the example above because it has some other crazy/confusing/distracting bash magic going on also.
You can do:
hash=$(genhash --use-ssl -s $IP -p 443 --url $URL)
or
hash=`genhash --use-ssl -s $IP -p 443 --url $URL`
If you want to result of the entire pipe to be assigned to the variable, you can use the entire pipeline in the above assignments.
Source: Stackoverflow.com