[ssh_tools] tabssh: modernize

ssh_tools/tabssh.sh

@@ -12,39 +12,57 @@
 # Open an SSH interactive shell on a list of remote hosts, opening one
 # GNU Screen tab per host.
 
+#set -x
+set -u
+
+# Exit codes
+readonly EXIT_SUCCESS=0
+readonly EXIT_USAGE=127
+readonly EXIT_HOSTS_LIST=6
+
 print_usage()
 {
   echo "Usage: $0 [-l login] <hosts_list>"
 }
 
+bad_usage()
+{
+  err "$@"
+  echo >&2
+  print_usage >&2
+  exit $EXIT_USAGE
+}
+
+err()
+{
+  printf 'Error! ' >&2
+  printf '%s\n' "$@" >&2
+}
+
+LOGIN=
+
 # We must have either 3 arguments...
 if [ $# -eq 3 ] ; then
-  # Parse the optional arguments
-  if [ "$1" = "-l" ] ; then
-    LOGIN="$2"
-    shift
-    shift
-  else # Option unknown
-    print_usage
-    exit 1
-  fi
+  # Only -l is a valid option
+  [ "$1" = "-l" ] || bad_usage "Option '$1' unknown."
+  LOGIN="$2"
+  shift
+  shift
 
-# ... or only 1
+# ... or only 1 argument
 elif [ $# -ne 1 ] ; then
-  print_usage
-  exit 3
+  bad_usage "Wrong number of arguments."
 fi
 
-# Hosts' list file
-if [ -z "$XDG_CONFIG_HOME" ] ; then
-  XDG_CONFIG_HOME="$HOME/.config"
-fi
-HOSTS_FILE="$XDG_CONFIG_HOME/ssh_tools/$1.lst"
+# Hosts list file
+[ -z ${XDG_CONFIG_HOME+x} ] && XDG_CONFIG_HOME="$HOME/.config"
+HOSTS_LIST_NAME="$1"
 shift
-echo "Using file '$HOSTS_FILE' as hosts' list."
-if [ ! -f "$HOSTS_FILE" ] ; then
-  echo "The hosts' list file doesn't exist or is not a regular file."
-  exit 2
+HOSTS="$XDG_CONFIG_HOME/ssh_tools/${HOSTS_LIST_NAME}.lst"
+echo "Using file '$HOSTS' as hosts list."
+if [ ! -f "$HOSTS" ] ; then
+  err "The hosts list file doesn't exist or is not a regular file."
+  exit $EXIT_HOSTS_LIST
 fi
 
 # Login
@@ -58,4 +76,4 @@ while read -r HOST ; do
   SSH="ssh ${LOGIN}${HOST}"
   # shellcheck disable=SC2086
   screen -t "$SSH" $SSH
-done <"$HOSTS_FILE"
+done <"$HOSTS"