How to repeat a few characters a few times in bash?

In a bash script, I have to include the same file several times in a row as an argument. Like this:

convert image.png image.png image.png [...] many_images.png

where image.png should be repeated a few times.

Is there a bash shorthand for repeating a pattern?

From stackoverflow

• #!/bin/bash
  
  function repeat {
      for ((i=0;i<$2;++i)); do echo -n $1 " "; done
  }
  
  convert $(repeat image.png 3) many_images.png
  

• You can do this using brace expansion:

  convert image.png{,,} many_images.png
  

  will produce:

  convert image.png image.png image.png many_images.png
  

  Brace expansion will repeat the string(s) before (and after) the braces for each comma-separated string within the braces producing a string consiting of the prefix, the comma-separated string and the suffix; and separating the generated strings by a space.

  In this case the comma-separated string between the braces and the suffix are empty strings which will produce the string image.png three times.

  Philipp : This is the best solution for a fixed, small number of repetitions, but doesn't work well for a large or flexible number of repetitions.

  BastiBechtold : This is neat. I like this. But as Philipp mentioned, I kind of have to prefer a parametrized solution.

• Here is a solution that uses arrays and is thus robust for strings containing spaces, newlines etc.

  declare -a images
  declare -i count=5
  for ((i=0; i<count; ++i))
  do
      images+=(image.png)
  done
  convert "${images[@]}" many_images.png
  

  Dennis Williamson : You can get by without the `declare` statements. In your example, Bash will do the right thing for you. You would just set your count like this: `count=5`. The array will be created by virtue of the parentheses.

• This works with a given integer (10 in the example below).

  $ echo $(yes image.png | head -n10)
  image.png image.png image.png image.png image.png image.png image.png image.png image.png image.png
  

  It can also be used with xargs:

  $ yes image.png | head -n10 | xargs echo
  image.png image.png image.png image.png image.png image.png image.png image.png image.png image.png
  

  smichak : Yep - that's it...