added mode documentation on ZSTD_CLEVEL

providing range restriction [1-19] explicitly partially answering #1829
2019-10-18 17:22:45 -07:00
parent 8e715d57c5
commit ca73c218be
5 changed files with 22 additions and 6 deletions
@@ -214,6 +214,16 @@ the last one takes effect.
 * `--`:
    All arguments after `--` are treated as files

+### Restricted usage of Environment Variables
+
+Using environment variables to set parameters has security implications.
+Therefore, this avenue is intentionally restricted.
+Only `ZSTD_CLEVEL` is supported currently, for setting compression level.
+`ZSTD_CLEVEL` can be used to set the level between 1 and 19 (the "normal" range).
+If the value of `ZSTD_CLEVEL` is not a valid integer, it will be ignored with a warning message.
+`ZSTD_CLEVEL` just replaces the default compression level (`3`).
+It can be overridden by corresponding command line arguments.
+

 DICTIONARY BUILDER
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