View difference between Paste ID: Gak7x9rN and KvetfK3D

 # no file or directory with single uppercase letter name
-grep: f: Is a directory
+# unquoted grep parameter works correctly
-grep: h: Is a directory
+
-grep: j: Is a directory
+bash-4.2$ echo [A-Z]
-grep: m: Is a directory
+[A-Z]
-grep: q: Is a directory
+
-grep: r: Is a directory
+
-4
+72
 
 bash-4.2$ ls {/usr{/local,},}/{s,}bin | grep '[A-Z]' | wc -l
 72
 
 # file with single uppercase letter name
 # unquoted grep parameter leads to incorrect result
 
 bash-4.2$ touch A
 
 bash-4.2$ echo [A-Z]
 A
 
 bash-4.2$ ls {/usr{/local,},}/{s,}bin | grep [A-Z] | wc -l
 8
 
 bash-4.2$ ls {/usr{/local,},}/{s,}bin | grep '[A-Z]' | wc -l
 72
 
 # directory with single uppercase letter name
 # unquoted grep parameter leads to wrong result and error message
 
 bash-4.2$ mkdir B
 
 bash-4.2$ echo [A-Z]
 A B
 
 bash-4.2$ ls {/usr{/local,},}/{s,}bin | grep [A-Z] | wc -l
 grep: B: Is a directory
 0
 
 bash-4.2$ ls {/usr{/local,},}/{s,}bin | grep '[A-Z]' | wc -l
 72