How to split strings over multiple lines in Bash

Question

How can i split my long string constant over multiple lines  I realize that you can do this  echo  quot continuation   lines quot   gt continuation lines  However  if you have indented code  it doesn t work out so well      echo  quot continuation       lines quot   gt continuation     lines

User · Answer

In certain scenarios utilizing Bash s concatenation ability might be appropriate   Example   temp  this string is very long   temp   so I will separate it onto multiple lines  echo  temp this string is very long so I will separate it onto multiple lines   From the PARAMETERS section of the Bash Man page      name  value             In  the  context  where an assignment statement is assigning a value to a shell variable or array index  the    operator can be used to append to or add to the variable s previous value   When    is applied to a variable for             which the integer attribute has been set  value is evaluated as an arithmetic expression and added to the variable s current value  which is also evaluated   When    is applied to an array variable using compound  assignment              see  Arrays  below    the  variable s  value is not unset  as it is when using     and new values are appended to the array beginning at one greater than the array s maximum index  for indexed arrays  or added as additional             key-value pairs in an associative array   When applied to a string-valued variable  value is expanded and appended to the variable s value

User · Answer

However  if you have indented code  it doesn t work out so well       echo  continuation       lines   gt continuation     lines    Try with single quotes and concatenating the strings       echo  continuation         lines   gt continuation lines   Note  the concatenation includes a whitespace

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Here documents with the  lt  lt -HERE terminator work well for indented multi-line text strings  It will remove any leading tabs from the here document   Line terminators will still remain  though    cat  lt  lt -    HERE     continuation     lines     HERE   See also http   ss64 com bash syntax-here html  If you need to preserve some  but not all  leading whitespace  you might use something like  sed  s         lt  lt     HERE     This has four leading spaces      Two of them will be removed by sed      HERE   or maybe use tr to get rid of newlines   tr -d   012   lt  lt -         continuation      lines         The second line has a tab and a space up front  the tab will be removed by the dash operator before the heredoc terminator  whereas the space will be preserved    For wrapping long complex strings over many lines  I like printf   printf   s         This will all be printed on a          single line  because the format string          doesn t specify any newline     It also works well in contexts where you want to embed nontrivial pieces of shell script in another language where the host language s syntax won t let you use a here document  such as in a Makefile or Dockerfile   printf   s n   gt   myscript           bin sh         echo   G day  World           date   F   T   amp  amp    chmod a x   myscript  amp  amp      myscript

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This isn t exactly what the user asked  but another way to create a long string that spans multiple lines is by incrementally building it up  like so     greeting  Hello    greeting   greeting  World    echo  greeting Hello  World   Obviously in this case it would have been simpler to build it one go  but this style can be very lightweight and understandable when dealing with longer strings

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This is what you may want          echo  continuation    gt         lines  continuation lines   If this creates two arguments to echo and you only want one  then let s look at string concatenation   In bash  placing two strings next to each other concatenate     echo  continuation  lines  continuationlines   So a continuation line without an indent is one way to break up a string     echo  continuation    gt   lines  continuationlines   But when an indent is used           echo  continuation    gt         lines  continuation lines   You get two arguments because this is no longer a concatenation   If you would like a single string which crosses lines  while indenting but not getting all those spaces  one approach you can try is to ditch the continuation line and use variables     a  continuation    b  lines    echo  a b continuationlines   This will allow you to have cleanly indented code at the expense of additional variables   If you make the variables local it should not be too bad

User · Answer

I came across a situation in which I had to send a long message as part of a command argument and had to adhere to the line length limitation  The commands looks something like this   somecommand --message  I am a long message  args   The way I solved this is to move the message out as a here document  like  tripleee suggested   But a here document becomes a stdin  so it needs to be read back in  I went with the below approach   message        tr   n       lt  lt - END         This is a         long message END   somecommand --message   message  args   This has the advantage that  message can be used exactly as the string constant with no extra whitespace or line breaks   Note that the actual message lines above are prefixed with a tab character each  which is stripped by here document itself  because of the use of  lt  lt -   There are still line breaks at the end  which are then replaced by dd with spaces   Note also that if you don t remove newlines  they will appear as is when   message  is expanded  In some cases  you may be able to workaround by removing the double-quotes around  message  but the message will no longer be a single argument

User · Answer

You could simply separate it with newlines  without using backslash  as required within the indentation as follows and just strip of new lines   Example   echo  continuation of  lines    tr   n        Or if it is a variable definition newlines gets automatically converted to spaces  So  strip of extra spaces only if applicable   x  continuation of multiple lines  y  red blue  green yellow   echo  x   This will do as the converted space actually is meaningful echo  y   tr -d       Stripping of space may be preferable in this case

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Line continuations also can be achieved through clever use of syntax    In the case of echo     echo  -n  flag prevents trailing  lt CR gt   echo -n  This is my one-line statement    echo -n   that I would like to make   This is my one-line statement that I would like to make    In the case of vars    outp  This is my one-line statement     outp    that I would like to make      echo -n    outp   This is my one-line statement that I would like to make    Another approach in the case of vars    outp  This is my one-line statement     outp    outp  that I would like to make      echo -n    outp   This is my one-line statement that I would like to make    Voila

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You can use bash arrays    str array   continuation                lines     then    echo    str array      continuation lines   there is an extra space  because  after bash manual       If the word is double-quoted    name     expands to a single word with   the value of each array member separated by the first character of the   IFS variable   So set IFS    to get rid of extra space    IFS      echo    str array      continuationlines

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This probably doesn t really answer your question but you might find it useful anyway   The first command creates the script that s displayed by the second command   The third command makes that script executable   The fourth command provides a usage example   john malkovich   tmp so  echo      usr bin env python nimport textwrap  sys n ndef bash dedent text   n       Dedent all but the first line in the passed  text      n    try  n        first  rest   text split    n   1  n        return    n  join  first  textwrap dedent rest    n    except ValueError  n        return text    single-line string n nprint bash dedent sys argv 1      gt  bash dedent john malkovich   tmp so  cat bash dedent     usr bin env python import textwrap  sys  def bash dedent text          Dedent all but the first line in the passed  text          try          first  rest   text split   n   1          return   n  join  first  textwrap dedent rest        except ValueError          return text    single-line string  print bash dedent sys argv 1   john malkovich   tmp so  chmod a x bash dedent john malkovich   tmp so  echo      bash dedent  first line  gt      second line  gt      third line    first line second line third line   Note that if you really want to use this script  it makes more sense to move the executable script into   bin so that it will be in your path   Check the python reference for details on how textwrap dedent works   If the usage of        or          is confusing to you  ask another question  one per construct  if there s not already one up   It might be nice to provide a link to the question you find ask so that other people will have a linked reference

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Depending on what sort of risks you will accept and how well you know and trust the data  you can use simplistic variable interpolation      x       this     is        variably indented     stuff         echo   x    preserves the newlines and spacing      this     is        variably indented     stuff     echo  x   no quotes  stacks it  neatly  with minimal spacing this is variably indented stuff

[bash] How to split strings over multiple lines in Bash?

Example:

From the PARAMETERS section of the Bash Man page:

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