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Code Block
languagebash
# Function that checks if a directory exists and exits if not.
#   arg 1 - the directory name
#   arg 2 - text describing the directory (optional)
check_dir() {
  if [[ ! -d "$1" ]]; then err "$2 Directory '$1' not found"
  else maybe_echo ".. $2 directory '$1' exists"; fi
}
# Function that checks if a file exists
#   arg 1 - the file name
#   arg 2 - text describing the file (optional)
check_file() {
  if [[ ! -e "$1" ]]; then err "$2 File '$1' not found"
  else maybe_echo ".. $2 file '$1' exists"; fi
}
# Function checks if a file exists & has non-0 length, else exits.
#   arg 1 - the file name
#   arg 2 - text describing the file (optional)
check_file_not_empty() {
  if [[ ! -e "$1" ]]; then err "$2 File '$1' not found"
  elif [[ ! -s "$1" ]]; then err "$2 File '$1' is empty"
  else maybe_echo ".. $2 file '$1' exists and is not empty"; fi
}

See https://www.gnu.org/software/bash/manual/html_node/Bash-Conditional-Expressions.html for conditional expressions, and https://www.gnu.org/software/bash/manual/html_node/Conditional-Constructs.html for conditional constructs such as if or case.

exercise 1

Explore these file checking functions in the safety of a sub-shell.

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