docs: add hint on shell redirections (#5761)

diff --git a/docs/property/postprocessor.md b/docs/property/postprocessor.md
index 91fafd96db8827631c58158feb6dd4fc1322c83e..869b69ca168eae9371b8c08ce90ebbe04d48b42b 100644 (file)
--- a/docs/property/postprocessor.md
+++ b/docs/property/postprocessor.md
@@ -31,8 +31,15 @@ Format | Description                               | Example value
 
 *Example usage*
 
-To use special characters (e.g. spaces), either put the string in quotes or
-escape the individual characters.
+To use special characters (e.g. spaces), either put the string in double quotes
+or escape the individual characters.
 
 ```/path/to/ffmpeg -i "%f" -vcodec libx264 -acodec copy "/path/with white space/%b"```
 
+The command is executed as-is, without a shell. To redirect command output or
+chain commands, wrap the command in a shell, e.g.
+
+```
+sh -c "df -P -h /recordings >/config/.markers/recording-post-process"
+sh -c "df -P -h /recordings | tee /config/.markers/recording-post-process"
+```

diff --git a/docs/property/postremove.md b/docs/property/postremove.md
index 9ff0565a10afadb48d9874b376c96bc95cba949b..210cf099757b13c3e8a61d5bab693a1408ed06fc 100644 (file)
--- a/docs/property/postremove.md
+++ b/docs/property/postremove.md
@@ -26,7 +26,15 @@ Format | Description                               | Example value
 
 *Example usage*
 
-To use special characters (e.g. spaces), either put the string in quotes or
-escape the individual characters.
+To use special characters (e.g. spaces), either put the string in double quotes
+or escape the individual characters.
 
 ```/usr/bin/tvh_file_removed "%f"```
+
+The command is executed as-is, without a shell. To redirect command output or
+chain commands, wrap the command in a shell, e.g.
+
+```
+sh -c "df -P -h /recordings >/config/.markers/recording-post-remove"
+sh -c "df -P -h /recordings | tee /config/.markers/recording-post-remove"
+```

diff --git a/docs/property/preprocessor.md b/docs/property/preprocessor.md
index 3f8371dc96c304278fc0d0d8c535bf7fe13b4873..74730231ea9ba283c3bccfb942457df55b0275d6 100644 (file)
--- a/docs/property/preprocessor.md
+++ b/docs/property/preprocessor.md
@@ -24,7 +24,15 @@ Format | Description                               | Example value
 
 *Example usage*
 
-To use special characters (e.g. spaces), either put the string in quotes or
-escape the individual characters.
+To use special characters (e.g. spaces), either put the string in double quotes
+or escape the individual characters:
 
 ```/usr/bin/lcd_show "%f"```
+
+The command is executed as-is, without a shell. To redirect command output or
+chain commands, wrap the command in a shell, e.g.
+
+```
+sh -c "df -P -h /recordings >/config/.markers/recording-pre-process"
+sh -c "df -P -h /recordings | tee /config/.markers/recording-pre-process"
+```