How to output a multiline string in Bash

Question

How can I output a multipline string in Bash without using multiple echo calls like so   echo  usage  up  --level  lt n gt   -n  lt levels gt   --help  --version   echo  echo  Report bugs to    echo  up home page      I m looking for a portable way to do this  using only Bash builtins

User · Answer

Inspired by the insightful answers on this page, I created a mixed approach, which I consider the simplest and more flexible one. What do you think?

First, I define the usage in a variable, which allows me to reuse it in different contexts. The format is very simple, almost WYSIWYG, without the need to add any control characters. This seems reasonably portable to me (I ran it on MacOS and Ubuntu)

__usage="
Usage: $(basename $0) [OPTIONS]

Options:
  -l, --level <n>              Something something something level
  -n, --nnnnn <levels>         Something something something n
  -h, --help                   Something something something help
  -v, --version                Something something something version
"

Then I can simply use it as

echo "$__usage"

or even better, when parsing parameters, I can just echo it there in a one-liner:

levelN=${2:?"--level: n is required!""${__usage}"}

User · Answer

or you can do this   echo  usage  up  --level  lt n gt   -n  lt levels gt   --help  --version   Report bugs to   up home page

User · Answer

Use -e option  then you can print new line character with  n in the string   Sample  but not sure whether a good one or not   The fun thing is that -e option is not documented in MacOS s man page while still usable  It is documented in the man page of Linux

User · Answer

If you use the solution from  jorge and find that everything is on the same line  make sure you enclose the variable in quotes   echo    usage   will print everything on one line whereas  echo     usage    will retain the newlines

User · Answer

Here documents are often used for this purpose   cat  lt  lt  EOF usage  up  --level  lt n gt   -n  lt levels gt   --help  --version   Report bugs to   up home page  EOF   They are supported in all Bourne-derived shells including all versions of Bash

User · Answer

Also with indented source code you can use  lt  lt -  with a trailing dash  to ignore leading tabs  but not leading spaces   For example this  if   some test    then     cat  lt  lt - xx         line1         line2 xx fi  Outputs indented text without the leading whitespace  line1 line2

User · Answer

Since I recommended printf in a comment  I should probably give some examples of its usage  although for printing a usage message  I d be more likely to use Dennis  or Chris  answers    printf is a bit more complex to use than echo  Its first argument is a format string  in which escapes  like  n  are always interpreted  it can also contain format directives starting with    which control where and how any additional arguments are included in it   Here are two different approaches to using it for a usage message   First  you could include the entire message in the format string   printf  usage  up  --level  lt n gt   -n  lt levels gt   --help  --version  n nReport bugs to   nup home page   n    Note that unlike echo  you must include the final newline explicitly   Also  if the message happens to contain any   characters  they would have to be written as      If you wanted to include the bugreport and homepage addresses  they can be added quite naturally   printf  usage  up  --level  lt n gt   -n  lt levels gt   --help  --version  n nReport bugs to   s nup home page   s n    bugreport    homepage    Second  you could just use the format string to make it print each additional argument on a separate line   printf   s n   usage  up  --level  lt n gt   -n  lt levels gt   --help  --version       Report bugs to     up home page      With this option  adding the bugreport and homepage addresses is fairly obvious   printf   s n   usage  up  --level  lt n gt   -n  lt levels gt   --help  --version       Report bugs to   bugreport   up home page   homepage

User · Answer

One more thing  using printf with predefined var as template  msg  quot First line  s Second line  s Third line  s  quot   one  additional message for the first line  two  2  tri  this is the last one   printf  quot  msg quot   quot  one quot   quot  two quot   quot  tri quot   This     will print whole message with additional vars inserted instead of   s  in provided order

User · Answer

Use the -e argument and the escape character  n  echo -e  quot This will generate a next line  nThis new line is the result quot

[bash] How to output a multiline string in Bash?

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