Added POSIX compatible options without shellcheck warnings

Recursiveness.md

@@ -10,36 +10,32 @@ Script could have a `.sh` extension, no extension and have a range of shebang li
 
 The solution for this problem is to use `shellcheck` in combination with the `find` or `grep` command.
 
-## Without exit code
+## By extension
 
-If you're not interested in the exit code of the `shellcheck` command, you can use (a variation) of one of the following commands:
+To check files with one of multiple extensions:
 
 ```
-# Scan a complete folder (recursively)
-find path/to/scripts -type f -exec "shellcheck" "--format=gcc" {} \;
+# Bash 4+
+shopt -s globstar nullglob
+shellcheck /path/to/scripts/**/*.{sh,bash,ksh}
 
-# Scan a complete folder (recursively) for .sh files
-find path/to/scripts -type f -name "*.sh" -exec "shellcheck" "--format=gcc" {} \;
+# POSIX
+find /path/to/scripts -type f \( -name "*.sh" -o -name "*.bash" -o -name "*.ksh" \) -print |
+  while IFS="" read -r file
+  do
+    shellcheck "$file"
+  done
 ```
 
-## With exit code
+## By shebang
 
-If you want to use `shellcheck` in some kind of testing pipeline, you want to know the exit code of the command.
-
-In this case you can test every matched file individually:
+To check files whose shebang indicate that they are sh/bash/ksh scripts:
 
 ```
-# Scan a complete folder (recursively)
-for file in $(find path/to/scripts -type f); do shellcheck --format=gcc $file; done;
-
-# Scan a complete folder (recursively) for .sh files
-for file in $(find path/to/scripts -type f -name "*.sh"); do shellcheck --format=gcc $file; done;
-```
-
-## Finding files to test
-
-Since not all scripts have a `.sh` extension, you could use the shebang line of files to determine if they need to be tested (and with which format):
-
-```
-for file in $(grep -IRl "#\!\(/usr/bin/env \|/bin/\)sh" --exclude-dir "var" --exclude "*.txt"); do shellcheck --format=gcc --shell=sh $file; done;
+# POSIX
+find /path/to/scripts -type f -exec grep -Eq '^#!(.*/|.*env +)(sh|bash|ksh)' {} \; -print |
+  while IFS="" read -r file
+  do
+    shellcheck "$file"
+  done
 ```