Optimize directory checking

bin/list_all_entities_exported.sh

@@ -49,7 +49,7 @@ display_help () {
 	  LOG_LEVEL  The global log level [0..5]
 	
 	All of the above environment variables are REQUIRED
-	(except LOG_LEVEL, which defaults to LOG_LEVEL=3).
+	except LOG_LEVEL, which defaults to LOG_LEVEL=3.
 	
 	EXAMPLES
 	
@@ -64,51 +64,31 @@ HELP_MSG
 
 script_name=${0##*/}  # equivalent to basename $0
 
-# check the bin directory
-if [ -z "$BIN_DIR" ]; then
-	echo "ERROR: $script_name requires env var BIN_DIR" >&2
-	exit 2
-fi
-if [ ! -d "$BIN_DIR" ]; then
-	echo "ERROR: $script_name: directory does not exist: $BIN_DIR" >&2
-	exit 2
-fi
-
-# check the source lib directory
-if [ -z "$LIB_DIR" ]; then
-	echo "ERROR: $script_name requires env var LIB_DIR" >&2
-	exit 2
-fi
-if [ ! -d "$LIB_DIR" ]; then
-	echo "ERROR: $script_name: directory does not exist: $LIB_DIR" >&2
-	exit 2
-fi
-
-# check the cache directory
-if [ -z "$CACHE_DIR" ]; then
-	echo "ERROR: $script_name requires env var CACHE_DIR" >&2
-	exit 2
-fi
-if [ ! -d "$CACHE_DIR" ]; then
-	echo "ERROR: $script_name: directory does not exist: $CACHE_DIR" >&2
-	exit 2
-fi
-
-# check the tmp directory
-if [ -z "$TMPDIR" ]; then
-	echo "ERROR: $script_name requires env var TMPDIR" >&2
-	exit 2
-fi
-if [ ! -d "$TMPDIR" ]; then
-	echo "ERROR: $script_name: directory does not exist: $TMPDIR" >&2
-	exit 2
-fi
+# required directories
+env_vars="BIN_DIR
+LIB_DIR
+CACHE_DIR
+TMPDIR"
+
+# check required directories
+for env_var in $env_vars; do
+	eval "env_var_val=\${$env_var}"
+	if [ -z "$env_var_val" ]; then
+		echo "ERROR: $script_name requires env var $env_var" >&2
+		exit 2
+	fi
+	if [ ! -d "$env_var_val" ]; then
+		echo "ERROR: $script_name: directory does not exist: $env_var_val" >&2
+		exit 2
+	fi
+done
 
 # check the log file
 if [ -z "$LOG_FILE" ]; then
 	echo "ERROR: $script_name requires env var LOG_FILE" >&2
 	exit 2
 fi
+# devices such as /dev/tty and /dev/null are allowed
 if [ ! -f "$LOG_FILE" ] && [[ $LOG_FILE != /dev/* ]]; then
 	echo "ERROR: $script_name: file does not exist: $LOG_FILE" >&2
 	exit 2