add support for user-specified rules file

Author: psyb0t

README.md

@@ -154,15 +154,17 @@ sudo mv ssh-tunnel-swarm /usr/bin/
 
 ### Environment Variables
 
+- **RULES_FILE**: This can be used to specify the path to the file containing the tunnel rules. If this variable is not set, the default file path is set to `rules.txt`.
+
 - **LOG_ENABLED**: This acts as a master switch for the logger. If it's set to `1`, logging is enabled. A value of `0` disables logging. Default value if not set is `1`.
 
 - **LOG_FILE**: This determines the output destination of the log messages. If set, log messages will be written to the specified file. If not set, logs will be printed to stdout.
 
-- **LOG_LEVEL**: This determines the severity level of the messages to be logged. Messages with a severity level less than this will not be logged. For example, if `LOG_LEVEL` is set to `INFO`, then `DEBUG` messages won't be logged. Default value if not set is `DEBUG`.
+- **LOG_LEVEL**: This determines the severity level of the messages to be logged. Messages with a severity level less than this will not be logged. For example, if `LOG_LEVEL` is set to `INFO`, then `DEBUG` messages won't be logged. Default value if not set is `DEBUG`. You can find all of the [supported log levels here](#supported-log-levels).
 
 ### Tunnel Rules
 
-SSH Tunnel Swarm reads the tunnel rules from a file named `rules.txt` which contains the rules for each host. Each entry should include the username, hostname, port, and the tunnels to establish. For instance:
+SSH Tunnel Swarm reads the tunnel rules for each host from a file specified by the `RULES_FILE` environment variable. Each entry within the file should include the username, hostname, port, and the tunnels to establish. For instance:
 
 ```
 aparker@host789:34567
@@ -215,7 +217,13 @@ Now guess what happens when you try to connect to localhost:6366.
 
 ## Usage
 
-- coming up soon
+```shell
+RULES_FILE=/path/to/rules.txt \
+LOG_ENABLED=1 \
+LOG_FILE=/path/to/log/file \
+LOG_LEVEL=DEBUG \
+ssh-tunnel-swarm
+```
 
 ## Logging
 

logger.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
-# Set default log level to DEBUG
+# Set default log level to DEBUG if it's not already set
 : "${LOG_LEVEL:=DEBUG}"
 # Set default log enabled flag only if it's not been set before
 : "${LOG_ENABLED:=1}"

rules.sh

@@ -5,9 +5,12 @@ source logger.sh
 # Load validator functions
 source validators.sh
 
+# Set default rules file to rules.txt if it's not already set
+: "${RULES_FILE:=rules.txt}"
+
 declare -A RULES
 
-# This function loads the rules from rules.txt file into an associative array called RULES.
+# This function loads the rules from the rules file into an associative array called RULES.
 # The format of the rules file is:
 # <username>@<hostname/IP address>:<port>
 # <forward/reverse> <local address>:<local port>:<remote address>:<remote port>
@@ -18,13 +21,13 @@ declare -A RULES
 load_rules() {
     logger "DEBUG" "Starting load_rules function"
 
-    # Check if rules.txt exists and has content
-    if [ ! -f "rules.txt" ]; then
-        logger "FATAL" "rules.txt not found"
+    # Check if the rules file exists and has content
+    if [ ! -f "$RULES_FILE" ]; then
+        logger "FATAL" "Rules file \"$RULES_FILE\" not found"
     fi
 
-    if [ ! -s "rules.txt" ]; then
-        logger "FATAL" "rules.txt is empty"
+    if [ ! -s "$RULES_FILE" ]; then
+        logger "FATAL" "Rules file \"$RULES_FILE\" is empty"
     fi
 
     # Variable to keep track of the current host being processed
@@ -82,7 +85,7 @@ load_rules() {
             # Log an error for invalid lines
             logger "FATAL" "Invalid line in rules file: $line in line $line_no"
         fi
-    done <rules.txt
+    done <"$RULES_FILE"
 
     logger "DEBUG" "load_rules function finished"
 }