[ssh_tools] multissh: don't require pssh

ssh_tools/multissh.sh

@@ -17,7 +17,6 @@ set -u
 # Exit codes
 readonly EXIT_SUCCESS=0
 readonly EXIT_USAGE=127
-readonly EXIT_DEPENDENCY=4
 readonly EXIT_HOSTS_LIST=6
 
 print_usage()
@@ -39,6 +38,23 @@ err()
   printf '%s\n' "$@" >&2
 }
 
+warn()
+{
+  printf 'Warning! ' >&2
+  printf '%s\n' "$@" >&2
+}
+
+ssh_command()
+{
+  grep -v '^#' "$HOSTS" | while read -r host ; do
+    [ -z "$host" ] && continue
+    echo "Executing command on '$host'..."
+    # shellcheck disable=SC2086
+    ssh ${LOGIN} "${host}" -- "$@" </dev/null
+    # Note: </dev/null is to prevent ssh from swallowing stdin (see SC2095).
+  done
+}
+
 # Do we have at least a host list and a command?
 [ $# -lt 2 ] && bad_usage "Wrong number of arguments."
 
@@ -56,8 +72,7 @@ fi
 # Check dependencies
 PSSH=$(command -v parallel-ssh || command -v pssh)
 if [ -z "$PSSH" ] ; then
-  err "Parallel SSH (pssh) is required for this script to work."
-  exit $EXIT_DEPENDENCY
+  warn "Parallel SSH (pssh) is not available. Install it for best results."
 fi
 
 # Hosts list file
@@ -79,5 +94,9 @@ fi
 
 echo "Command:" "$@"
 
-# shellcheck disable=SC2086
-exec $PSSH --print $LOGIN -h "$HOSTS" -- "$@"
+if [ -n "$PSSH" ] ; then
+  # shellcheck disable=SC2086
+  exec $PSSH --print $LOGIN -h "$HOSTS" -- "$@"
+else
+  ssh_command "$@"
+fi