Better help and error management

- Added set -euo pipefail for improved error handling and script safety.
- Added --help option and better usage messaging.
- Checks for required tools (unzip, unrar, 7z, etc.) before extraction.

extract

@@ -1,19 +1,46 @@
 #!/bin/bash
-if [ -f $1 ] ; then
-    case $1 in
-      *.tar.bz2)   tar xjf $1   ;;
-      *.tar.gz)    tar xzf $1   ;;
-      *.bz2)       bunzip2 $1   ;;
-      *.rar)       unrar x $1     ;;
-      *.gz)        gunzip $1    ;;
-      *.tar)       tar xf $1    ;;
-      *.tbz2)      tar xjf $1   ;;
-      *.tgz)       tar xzf $1   ;;
-      *.zip)       unzip $1     ;;
-      *.Z)         uncompress $1;;
-      *.7z)        7z x $1      ;;
-      *)           echo "'$1' cannot be extracted" ;;
-    esac
-  else
-    echo "'$1' invalid file"
-  fi
+set -euo pipefail
+IFS=$'\n\t'
+
+usage() {
+  echo "Usage: $0 <archive-file>"
+  echo "Extract supported archive formats: .tar.gz, .zip, .rar, .7z, etc."
+}
+
+check_command() {
+  local cmd="$1"
+  if ! command -v "$cmd" &>/dev/null; then
+    echo "Error: required command '$cmd' not found."
+    exit 3
+  fi
+}
+
+if [[ $# -eq 0 || "$1" == "--help" ]]; then
+  usage
+  exit 0
+fi
+
+file="$1"
+
+if [[ ! -f "$file" ]]; then
+  echo "Error: '$file' is not a valid file."
+  exit 2
+fi
+
+case "$file" in
+  *.tar.bz2)  check_command tar;      tar xjf "$file" ;;
+  *.tar.gz)   check_command tar;      tar xzf "$file" ;;
+  *.bz2)      check_command bunzip2;  bunzip2 "$file" ;;
+  *.rar)      check_command unrar;    unrar x "$file" ;;
+  *.gz)       check_command gunzip;   gunzip "$file" ;;
+  *.tar)      check_command tar;      tar xf "$file" ;;
+  *.tbz2)     check_command tar;      tar xjf "$file" ;;
+  *.tgz)      check_command tar;      tar xzf "$file" ;;
+  *.zip)      check_command unzip;    unzip "$file" ;;
+  *.Z)        check_command uncompress; uncompress "$file" ;;
+  *.7z)       check_command 7z;       7z x "$file" ;;
+  *)
+    echo "Error: '$file' has an unsupported file extension."
+    exit 1
+    ;;
+esac