Using variables inside a bash heredoc

by

In answer to your first question, there’s no parameter substitution because you’ve put the delimiter in quotes – the bash manual says:

The format of here-documents is:

      <<[-]word
              here-document
      delimiter

No parameter expansion, command substitution, arithmetic expansion, or
pathname expansion is performed on word. If any characters in word are
quoted, the delimiter is the result of quote removal on word, and the
lines in the here-document are not expanded. If word is unquoted, all
lines of the here-document are subjected to parameter expansion, command substitution, and arithmetic expansion. […]

If you change your first example to use <<EOF instead of << "EOF" you’ll find that it works.

In your second example, the shell invokes sudo only with the parameter cat, and the redirection applies to the output of sudo cat as the original user. It’ll work if you try:

sudo sh -c "cat > /path/to/outfile" <<EOT
my text...
EOT

More Related Contents:

  1. Are shell scripts sensitive to encoding and line endings?
  2. Difference between sh and Bash
  3. Dynamic variable names in Bash
  4. Pass commands as input to another command (su, ssh, sh, etc)
  5. Why would a correct shell script give a wrapped/truncated/corrupted error message? [duplicate]
  6. Why does my Bash code fail when I run it with ‘sh’?
  7. What is the benefit of using $() instead of backticks in shell scripts? [duplicate]
  8. How to store standard error in a variable
  9. How can I declare and use Boolean variables in a shell script?
  10. What is the meaning of the ${0##…} syntax with variable, braces and hash character in bash?
  11. How to assign a heredoc value to a variable in Bash?
  12. Ubuntu says “bash: ./program Permission denied” [closed]
  13. Length of string in bash
  14. What is the difference between “$@” and “$*” in Bash? [duplicate]
  15. Count occurrences of a char in a string using Bash
  16. How to redirect output of an entire shell script within the script itself?
  17. What is the exact meaning of IFS=$’\n’?
  18. Parsing variables from config file in Bash
  19. How can I reference a file for variables using Bash?
  20. How to do a logical OR operation for integer comparison in shell scripting?
  21. How to list variables declared in script in bash?
  22. Bash variables with spaces
  23. What does it mean in shell when we put a command inside dollar sign and parentheses: $(command)
  24. Bash script store command output into variable
  25. osascript using bash variable with a space
  26. sed replace with variable with multiple lines [duplicate]
  27. Forward function declarations in a Bash or a Shell script?
  28. Expand variables in sed
  29. Is there an elegant way to store and evaluate return values in bash scripts?
  30. Bash: warning: here-document at line delimited by end-of-file (wanted `EOF’) [duplicate]

Leave a Comment