How can I have a newline in a string in sh

Question

This  STR  Hello nWorld  echo  STR   produces as output  Hello nWorld   instead of  Hello World   What should I do to have a newline in a string   Note  This question is not about echo  I m aware of echo -e  but I m looking for a solution that allows passing a string  which includes a newline  as an argument to other commands that do not have a similar option to interpret  n s as newlines

User · Answer

On my system  Ubuntu 17 10  your example just works as desired  both when typed from the command line  into sh  and when executed as a sh script    bash    sh   STR  Hello nWorld    echo  STR Hello World   exit  bash    echo  STR   Hello nWorld    gt  echo   STR   gt  test-str sh  bash    cat test-str sh  STR  Hello nWorld  echo  STR  bash    sh test-str sh  Hello World   I guess this answers your question  it just works    I have not tried to figure out details such as at what moment exactly the substitution of the newline character for  n happens in sh    However  i noticed that this same script would behave differently when executed with bash and would print out Hello nWorld instead    bash    bash test-str sh Hello nWorld   I ve managed to get the desired output with bash as follows    bash    STR  Hello  gt  World   bash    echo   STR    Note the double quotes around  STR  This behaves identically if saved and run as a bash script   The following also gives the desired output    bash    echo  Hello  gt  World

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I m no bash expert  but this one worked for me   STR1  Hello  STR2  World  NEWSTR   cat  lt  lt  EOF  STR1   STR2 EOF   echo   NEWSTR    I found this easier to formatting the texts

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Disclaimer  I first wrote this and then stumbled upon this question  I thought this solution wasn t yet posted  and saw that tlwhitec did post a similar answer  Still I m posting this because I hope it s a useful and thorough explanation  Short answer  This seems quite a portable solution  as it works on quite some shells  see comment   This way you can get a real newline into a variable  The benefit of this solution is that you don t have to use newlines in your source code  so you can indent your code any way you want  and the solution still works  This makes it robust  It s also portable    Robust way to put a real newline in a variable  bash  dash  ksh  zsh  indentation-resistant   nl  quot   printf   nq   quot  nl   nl q   Longer answer  Explanation of the above solution  The newline would normally lost due to command substitution  but to prevent that  we add a  q  and remove it afterwards   The reason for the double quotes is explained further below   We can prove that the variable contains an actual newline character  0x0A   printf   s   quot  nl quot    hexdump -C 00000000  0a      00000001   Note that the   s  was needed  otherwise printf will translate a literal   n  string into an actual 0x0A character  meaning we would prove nothing   Of course  instead of the solution proposed in this answer  one could use this as well  but      nl          but that s less robust and can be easily damaged by accidentally indenting the code  or by forgetting to dedent it afterwards  which makes it inconvenient to use in  indented  functions  whereas the earlier solution is robust  Now  as for the double quotes  The reason for the double quotes  quot  surrounding the command substitution as in nl  quot   printf   nq   quot  is that you can then even prefix the variable assignment with the local keyword or builtin  such as in functions   and it will still work on all shells  whereas otherwise the dash shell would have trouble  in the sense that dash would otherwise lose the  q  and you d end up with an empty  nl  variable  again  due to command substitution   That issue is better illustrated with another example  dash trouble example         e   echo hello world    Not using  local       echo  quot  e quot    Fine  Outputs  hello world  in all shells       local e   echo hello world    But now  when using  local  without double quotes          echo  quot  e quot        oops  outputs just  hello  in dash                      but  hello world  in bash and zsh       local f  quot   echo hello world  quot    Finally  using  local  and surrounding with double quotes      echo  quot  f quot    Solved  Outputs  hello world  in dash  zsh  and bash         So back to our newline example  if we want to use  local   we need       double quotes to surround the command substitution         If we didn t use double quotes here  then in dash the  nl  variable       would be empty       local nl  quot   printf   nq   quot      nl   nl q     Practical example of the above solution    Parsing lines in a for loop by setting IFS to a real newline character   nl  quot   printf   nq   quot  nl   nl q   IFS  nl  for i in   printf   b   this is line 1 nthis is line 2    do     echo  quot i  i quot  done    Desired output    i this is line 1   i this is line 2    Exercise    Try running this example without the IFS  nl assignment  and predict the outcome

User · Answer

A   right before single quotation marks      n     as follows  however double quotation marks doesn t work     echo   Hello nWorld  Hello World   echo   Hello nWorld  Hello nWorld

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If you re using Bash  the solution is to use   string   for example    STR   Hello nWorld    echo  quot  STR quot    quotes are required here  Hello World  If you re using pretty much any other shell  just insert the newline as-is in the string    STR  Hello  gt  World   Bash is pretty nice  It accepts more than just  n in the     string  Here is an excerpt from the Bash manual page     Words of the form   string  are treated specially   The word expands to    string  with backslash-escaped characters replaced as specified by  the    ANSI  C  standard   Backslash escape sequences  if present  are decoded    as follows             a     alert  bell             b     backspace            e            E     an escape character            f     form feed            n     new line            r     carriage return            t     horizontal tab            v     vertical tab                  backslash                  single quote             quot      double quote            nnn   the eight-bit character whose value is  the  octal  value                  nnn  one to three digits             xHH   the  eight-bit  character  whose value is the hexadecimal                  value HH  one or two hex digits             cx    a control-x character     The expanded result is single-quoted  as if the  dollar  sign  had  not    been present      A double-quoted string preceded by a dollar sign    quot string quot   will cause    the string to be translated according to the current  locale    If  the    current  locale  is  C  or  POSIX   the dollar sign is ignored   If the    string is translated and replaced  the replacement is double-quoted

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The problem isn t with the shell   The problem is actually with the echo command itself  and the lack of double quotes around the variable interpolation   You can try using echo -e but that isn t supported on all platforms  and one of the reasons printf is now recommended for portability   You can also try and insert the newline directly into your shell script  if a script is what you re writing  so it looks like        bin sh echo  Hello World   EOF   or equivalently     bin sh string  Hello World  echo   string     note double quotes

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I wasn t really happy with any of the options here  This is what worked for me   str   printf   s   first line   str   printf   str n s   another line   str   printf   str n s   and another line

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Those picky ones that need just the newline and despise the multiline code that breaks indentation  could do   IFS    printf   nx    IFS    IFS x     Bash  and likely other shells  gobble all the trailing newlines after command substitution  so you need to end the printf string with a non-newline character and delete it afterwards  This can also easily become a oneliner   IFS    printf   nx    IFS    IFS x        I know this is two actions instead of one  but my indentation and portability OCD is at peace now    I originally developed this to be able to split newline-only separated output and I ended up using a modification that uses  r as the terminating character  That makes the newline splitting work even for the dos output ending with  r n   IFS    printf   n r

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I find the -e flag elegant and straight forward  bash  STR  Hello nWorld   bash  echo -e  STR Hello World   If the string is the output of another command  I just use quotes  indexes diff   git diff index yaml  echo   indexes diff

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The only simple alternative is to actually type a new line in the variable     STR  new line    printf   s    STR  new line   Yes  that means writing Enter where needed in the code  There are several equivalents to a new line character     n               A common way to represent a new line character   012             Octal value of a new line character   x0A             Hexadecimal value of a new line character    But all those require  an interpretation  by some tool  POSIX printf    echo -e  new nline                on POSIX echo   -e  is not required  printf  new nline                 Understood by POSIX printf  printf  new 012line               Valid in POSIX printf  printf  new x0Aline         printf   b   new 0012line         Valid in POSIX printf    And therefore  the tool is required to build a string with a new-line     STR    printf  new nline      printf   s    STR  new line  In some shells  the sequence    is an special shell expansion   Known to work in ksh93  bash and zsh     STR   new nline   Of course  more complex solutions are also possible     echo  6e65770a6c696e650a    xxd -p -r new line   Or      echo  new line    sed  s      n g  new line

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This isn t ideal  but I had written a lot of code and defined strings in a way similar to the method used in the question  The accepted solution required me to refactor a lot of the code so instead  I replaced every  n with  quot    n  quot  and this worked for me

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Echo is so nineties and so fraught with perils that its use should result in core dumps no less than 4GB  Seriously  echo s problems were the reason why the Unix Standardization process finally invented the printf utility  doing away with all the problems   So to get a newline in a string   FOO  hello world  BAR   printf  hello nworld n     Alternative  note  final newline is deleted printf   lt  s gt  n    FOO  printf   lt  s gt  n    BAR    There  No SYSV vs BSD echo madness  everything gets neatly printed and fully portable support for C escape sequences  Everybody please use printf now and never look back

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What I did based on the other answers was  NEWLINE    n  my var    between eggs and bacon    echo  spam  NEWLINE eggs  my var bacon  NEWLINE knight     which outputs  spam eggs  between eggs and bacon  bacon knight

[sh] How can I have a newline in a string in sh?

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