How can I write a heredoc to a file in Bash script

Question

How can I write a here document to a file in Bash script

User · Answer

Note    the following condenses and organizes other answers in this thread  esp the excellent work of Stefan Lasiewski and Serge Stroobandt Lasiewski and I recommend Ch 19  Here Documents  in the Advanced Bash-Scripting Guide   The question  how to write a here document  aka heredoc  to a file in a bash script   has  at least  3 main independent dimensions or subquestions    Do you want to overwrite an existing file  append to an existing file  or write to a new file  Does your user or another user  e g   root  own the file  Do you want to write the contents of your heredoc literally  or to have bash interpret variable references inside your heredoc     There are other dimensions subquestions which I don t consider important  Consider editing this answer to add them   Here are some of the more important combinations of the dimensions of the question listed above  with various different delimiting identifiers--there s nothing sacred about EOF  just make sure that the string you use as your delimiting identifier does not occur inside your heredoc    To overwrite an existing file  or write to a new file  that you own  substituting variable references inside the heredoc   cat  lt  lt  EOF  gt   path to your file This line will write to the file    THIS  will also write to the file  with the variable contents substituted  EOF  To append an existing file  or write to a new file  that you own  substituting variable references inside the heredoc   cat  lt  lt  FOE  gt  gt   path to your file This line will write to the file    THIS  will also write to the file  with the variable contents substituted  FOE  To overwrite an existing file  or write to a new file  that you own  with the literal contents of the heredoc   cat  lt  lt   END OF FILE   gt   path to your file This line will write to the file    THIS  will also write to the file  without the variable contents substituted  END OF FILE  To append an existing file  or write to a new file  that you own  with the literal contents of the heredoc   cat  lt  lt   eof   gt  gt   path to your file This line will write to the file    THIS  will also write to the file  without the variable contents substituted  eof  To overwrite an existing file  or write to a new file  owned by root  substituting variable references inside the heredoc   cat  lt  lt  until it ends   sudo tee  path to your file This line will write to the file    THIS  will also write to the file  with the variable contents substituted  until it ends  To append an existing file  or write to a new file  owned by user foo  with the literal contents of the heredoc   cat  lt  lt   Screw you Foo    sudo -u foo tee -a  path to your file This line will write to the file    THIS  will also write to the file  without the variable contents substituted  Screw you Foo

User · Answer

As instance you could use it   First making ssh connection    while read pass port user ip files directs  do     sshpass -p pass scp -o  StrictHostKeyChecking no  -P  port  files  user  ip  directs done  lt  lt     HERE     PASS    PORT    USER    IP    FILES    DIRECTS                                                                                                                                                     PASS    PORT    USER    IP    FILES    DIRECTS     HERE   Second executing commands    while read pass port user ip  do     sshpass -p pass ssh -p  port  user  ip  lt  lt ENDSSH1     COMMAND 1                       COMMAND n ENDSSH1 done  lt  lt     HERE     PASS    PORT    USER    IP                                                                                                  PASS    PORT    USER    IP         HERE   Third executing commands    Script     Your commands    while read pass port user ip  do     sshpass -p pass ssh -o  StrictHostKeyChecking no  -p  port  user  ip   Script   done  lt  lt    HERE PASS    PORT    USER    IP                                                                                  PASS    PORT    USER    IP      HERE   Forth using variables    while read pass port user ip fileoutput  do     sshpass -p pass ssh -o  StrictHostKeyChecking no  -p  port  user  ip fileinput  fileinput  bash -s  lt  lt ENDSSH1      Your command  gt   fileinput      Your command  gt   fileinput ENDSSH1 done  lt  lt     HERE     PASS    PORT    USER    IP      FILE-OUTPUT                                                                                                                                   PASS    PORT    USER    IP      FILE-OUTPUT     HERE

User · Answer

I like this method for concision  readability and presentation in an indented script    lt  lt -End of file  gt file         foo bar End of file   Where                 is a tab character

User · Answer

For future people who may have this issue the following format worked    cat  lt  lt -  EOF          LogFile  var log clamd log         LogTime yes         DatabaseDirectory  var lib clamav         LocalSocket  tmp clamd socket         TCPAddr 127 0 0 1         SelfCheck 1020         ScanPDF yes          EOF     gt   etc clamd conf

User · Answer

Instead of using cat and I O redirection it might be useful to use tee instead   tee newfile  lt  lt EOF line 1 line 2 line 3 EOF   It s more concise  plus unlike the redirect operator it can be combined with sudo if you need to write to files with root permissions

User · Answer

If you want to keep the heredoc indented for readability    perl -pe  s   s      lt  lt  EOF      line 1      line 2 EOF  The built-in method for supporting indented heredoc in Bash only supports leading tabs  not spaces  Perl can be replaced with awk to save a few characters  but the Perl one is probably easier to remember if you know basic regular expressions

User · Answer

To build on  Livven s answer  here are some useful combinations    variable substitution  leading tab retained  overwrite file  echo to stdout  tee  path to file  lt  lt EOF   variable  EOF  no variable substitution  leading tab retained  overwrite file  echo to stdout  tee  path to file  lt  lt  EOF    variable  EOF  variable substitution  leading tab removed  overwrite file  echo to stdout  tee  path to file  lt  lt -EOF       variable  EOF  variable substitution  leading tab retained  append to file  echo to stdout  tee -a  path to file  lt  lt EOF   variable  EOF  variable substitution  leading tab retained  overwrite file  no echo to stdout  tee  path to file  lt  lt EOF  gt  dev null   variable  EOF  the above can be combined with sudo as well  sudo -u USER tee  path to file  lt  lt EOF   variable  EOF

User · Answer

Read the Advanced Bash-Scripting Guide Chapter 19  Here Documents   Here s an example which will write the contents to a file at  tmp yourfilehere  cat  lt  lt  EOF  gt   tmp yourfilehere These contents will be written to the file          This line is indented  EOF   Note that the final  EOF   The LimitString  should not have any whitespace in front of the word  because it means that the LimitString will not be recognized   In a shell script  you may want to use indentation to make the code readable  however this can have the undesirable effect of indenting the text within your here document  In this case  use  lt  lt -  followed by a dash  to disable leading tabs  Note that to test this you will need to replace the leading whitespace with a tab character  since I cannot print actual tab characters here       usr bin env bash  if true   then     cat  lt  lt - EOF  gt   tmp yourfilehere     The leading tab is ignored      EOF fi   If you don t want to interpret variables in the text  then use single quotes   cat  lt  lt   EOF   gt   tmp yourfilehere The variable  FOO will not be interpreted  EOF   To pipe the heredoc through a command pipeline   cat  lt  lt  EOF     sed  s a b   foo bar baz EOF   Output   foo bbr bbz       or to write the the heredoc to a file using sudo   cat  lt  lt  EOF     sed  s a b     sudo tee  etc config file conf foo bar baz EOF

User · Answer

When root permissions are required When root permissions are required for the destination file  use  sudo tee instead of  gt   cat  lt  lt   EOF   sudo tee  tmp yourprotectedfilehere The variable  FOO will  not  be interpreted  EOF  cat  lt  lt   quot EOF quot   sudo tee  tmp yourprotectedfilehere The variable  FOO  will  be interpreted  EOF

[bash] How can I write a heredoc to a file in Bash script?

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