Add debug-log documentation and enable it by default

README.md

@@ -419,10 +419,9 @@ file and any changes that may have been made.
 
 sgminer will log to stderr if it detects stderr is being redirected to a
 file. To enable logging simply append `2>logfile.txt` to your command line
-and `logfile.txt` will contain the logged output at the log level you
-specify (normal, verbose, debug etc.). If you use the `--debug-log` option
-then everything will be logged to the file (console output will remain as
-configured).
+and `logfile.txt` will contain all debug output unless you set `debug-log`
+to `false`, in which case it will only contain output at the log level you
+specified (notice by default).
 
 There is also the -m option on Linux which will spawn a command of your choice
 and pipe the output directly to that command.

doc/configuration.md

@@ -456,6 +456,7 @@ sgminer 4.2.1-116-g2e8b-dirty
 * [Miscellaneous Options](#miscellaneous-options)
   * [compact](#compact)
   * [debug](#debug)
+  * [debug-log](#debug-log)
   * [default-profile](#default-profile)
   * [device](#device)
   * [difficulty-multiplier](#difficulty-multiplier)
@@ -1793,6 +1794,22 @@ Enable debug output.
 
 [Top](#configuration-and-command-line-options) :: [Config-file and CLI options](#config-file-and-cli-options) :: [Miscellaneous Options](#miscellaneous-options)
 
+### debug-log
+
+Enable debug logging when stderr is redirected to file.
+
+*Available*: Global
+
+*Config File Syntax:* `"debug-log":false`
+
+*Command Line Syntax:* `--debug-log`
+
+*Argument:* None
+
+*Default:* `true`
+
+[Top](#configuration-and-command-line-options) :: [Config-file and CLI options](#config-file-and-cli-options) :: [Miscellaneous Options](#miscellaneous-options)
+
 ### default-profile
 
 Use this profile for sgminer's default settings.

sgminer.c

@@ -8202,6 +8202,9 @@ int main(int argc, char *argv[])
   sigaction(SIGINT, &handler, &inthandler);
 #endif
 
+  /* enable debug output to file by default is stderr is redirected to a file */
+  opt_debug = !isatty(fileno((FILE *)stderr));
+
   /* opt_kernel_path defaults to SGMINER_PREFIX */
   opt_kernel_path = (char *)alloca(PATH_MAX);
   strcpy(opt_kernel_path, SGMINER_PREFIX);