How do I redirect output to a variable in shell

Question

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

User · Answer

read hash  lt   lt  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    http   www linuxjournal com content shell-process-redirection http   tldp org LDP abs html process-sub html http   tldp org LDP abs html commandsub html   for comparison

User · Answer

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

User · Answer

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  amp  save into 1 command  Regards

User · Answer

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

User · Answer

Use the          construct   hash   genhash --use-ssl -s  IP -p 443 --url  URL   grep MD5   grep -c  MD5

User · Answer

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

User · Answer

TL DR To store  quot abc quot  into  foo  echo  quot abc quot    read foo  But  because pipes create forks  you have to use  foo before the pipe ends  so    echo  quot abc quot      read foo  date   quot I received  foo on  D quot       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  The answer to the question is to use the read command  Here s how you do it   I would usually do this on one line  but for readability    series   of   commands           read string    mystic command --opt  quot  string quot   path to file         handle mystified file  Here is what it is doing and why it is important   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  quot sub shell quot  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  quot  string quot   path to file    handle mystified file    ugly and unreadable alternative mystic command --opt  quot   series   of   commands  quot   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

User · Answer

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

[bash] How do I redirect output to a variable in shell?

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