Strings

Testing if a string ends with a sub string

Here, I test if the passed argument to the function ends with .zip:

function check_if_file_is_a_zip_archive() {
  if [[ $1 == *.zip ]]; then
    echo $1 is a ZIP archive
  else
    echo $1 is not a ZIP
  fi
}

Search and replace in a string

Say you have the string "hello brave new world" and you want to replace all spaces with a hyphen. It's quite common for people to shell out a sub process to let sed search and replace a string for us:

greeting="hello brave new world"
echo ${greeting} | sed 's# #-#g'

There's no need to go to that drastic measures, however, BASH has string search and replace already built in: greeting="hello brave new world"

echo ${greeting// /-}

The and fields can themselves be variables:

greeting="hello brave new world"
from=" "
to="-"
echo ${greeting//${from}/${to}}

If you replace the double slash with a single one, BASH will only replace the first occurrence.

Neat, eh?

Newline handling

Here, I demonstrate storing a newline character and using it for string concatination, storing this in a variable and outputting it with the newline intact.

NEW_LINE=$'\n'

my_string="hi"
my_string=${my_string}${NEW_LINE}"world"

# newline intact
echo "${my_string}"

#without newline
echo ${my_string}

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