How to assign a heredoc value to a variable in Bash

Question

I have this multi-line string  quotes included    abc asdf    dont-execute-this  foo bar      How would I assign it to a variable using a heredoc in Bash   I need to preserve newlines   I don t want to escape the characters in the string  that would be annoying

User · Answer

Branching off Neil s answer  you often don t need a var at all  you can use a function in much the same way as a variable and it s much easier to read than the inline or read-based solutions     complex message       cat  lt  lt  EOF  abc asdf    dont-execute-this  foo bar    EOF      echo  This is a   complex message   This is a abc asdf    dont-execute-this  foo bar

User · Answer

Thanks to dimo414 s answer  this shows how his great solution works  and shows that you can have quotes and variables in the text easily as well   example output      test sh  The text from the example function is    Welcome dev  Would you  like  to know how many  files  there are in  tmp     There are        38  files in  tmp  according to the  wc  command   test sh     bin bash  function text1       COUNT    ls  tmp   wc -l  cat  lt  lt EOF     1 Would you  like  to know how many  files  there are in  tmp     There are   COUNT  files in  tmp  according to the  wc  command  EOF    function main       OUT   text1  Welcome dev      echo  The text from the example function is   OUT     main

User · Answer

assign a heredoc value to a variable  VAR    cat  lt  lt  VAREOF  abc asdf    dont-execute-this  foo bar    VAREOF      used as an argument of a command  echo    cat  lt  lt  SQLEOF  xxx  xxx xxx xx  123123    123123 abc asdf    dont-execute-this  foo bar    SQLEOF

User · Answer

this is variation of Dennis method  looks more elegant in the scripts   function definition   define    IFS   n  read -r -d      1     true      usage   define VAR  lt  lt  EOF  abc asdf    dont-execute-this  foo bar    EOF  echo   VAR    enjoy  p s  made a  read loop  version for shells that do not support read -d  should work with set -eu and unpaired backticks  but not tested very well   define    o   while IFS   n  read -r a  do o   o a      done  eval   1   o

User · Answer

Use     to assign the output of cat to your variable like this   VAR   cat  lt  lt  END HEREDOC  abc asdf    dont-execute-this  foo bar    END HEREDOC      this will echo variable with new lines intact echo   VAR    this will echo variable without new lines  changed to space character  echo  VAR   Making sure to delimit starting END HEREDOC with single-quotes   Note that ending heredoc delimiter END HEREDOC must be alone on the line  hence ending parenthesis is on the next line    Thanks to  ephemient for the answer

User · Answer

TEST  ok  read MYTEXT  lt  lt EOT this bash trick should preserve newlines  TEST long live perl EOT echo -e  MYTEXT

User · Answer

There is still no solution that preserves newlines    This is not true - you re probably just being misled by the behaviour of echo   echo  VAR   strips newlines  echo   VAR    preserves newlines

User · Answer

An array is a variable  so in that case mapfile will work mapfile y  lt  lt  z  abc asdf quot    dont-execute-this  foo quot bar quot    z  Then you can print like this printf  s  quot   y     quot

User · Answer

VAR  lt  lt END abc END   doesn t work because you are redirecting stdin to something that doesn t care about it  namely the assignment  export A  cat  lt  lt END sdfsdf sdfsdf sdfsfds END     echo  A   works  but there s a back-tic in there that may stop you from using this  Also  you should really avoid using backticks  it s better to use the command substitution notation         export A   cat  lt  lt END sdfsdf sdfsdf sdfsfds END     echo  A

User · Answer

I found myself having to read a string with NULL in it  so here is a solution that will read anything you throw at it   Although if you actually are dealing with NULL  you will need to deal with that at the hex level     cat   read dd sh  read dd          buf        while read  do         buf   REPLY      done  lt   lt   dd bs 1 2 gt  dev null   xxd -p         printf -v REPLY   b     sed  s        x amp  g   lt  lt  lt   buf       Proof       read dd sh   read dd  lt  read dd sh   echo -n   REPLY   gt  read dd sh copy   diff read dd sh read dd sh copy    echo  File are different       HEREDOC example  with  J   M   I      read dd  lt  lt  HEREDOC   gt         TAB   gt         SPACES    J  M  M   gt  DONE  gt   gt  HEREDOC    declare -p REPLY declare -- REPLY     TAB         SPACES    M  DONE       declare -p REPLY   xxd 0000000  6465 636c 6172 6520 2d2d 2052 4550 4c59  declare -- REPLY 0000010  3d22 0928 5441 4229 0a20 2020 2020 2028      TAB          0000020  5350 4143 4553 290a 285e 4a29 0d28 5e4d  SPACES    J    M 0000030  290a 444f 4e45 0a0a 220a                   DONE

User · Answer

You can avoid a useless use of cat and handle mismatched quotes better with this     read -r -d    VAR  lt  lt  EOF  abc asdf    dont-execute-this  foo bar    EOF   If you don t quote the variable when you echo it  newlines are lost  Quoting it preserves them     echo   VAR  abc asdf    dont-execute-this  foo bar      If you want to use indentation for readability in the source code  use a dash after the less-thans  The indentation must be done using only tabs  no spaces      read -r -d    VAR  lt  lt - EOF      abc asdf        dont-execute-this      foo bar        EOF   echo   VAR  abc asdf    dont-execute-this  foo bar      If  instead  you want to preserve the tabs in the contents of the resulting variable  you need to remove tab from IFS  The terminal marker for the here doc  EOF  must not be indented     IFS    read -r -d    VAR  lt  lt  EOF      abc asdf        dont-execute-this      foo bar    EOF   echo   VAR      abc asdf        dont-execute-this      foo bar      Tabs can be inserted at the command line by pressing Ctrl-V Tab  If you are using an editor  depending on which one  that may also work or you may have to turn off the feature that automatically converts tabs to spaces

[bash] How to assign a heredoc value to a variable in Bash?

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