Updated Sc2086 (markdown)

Sc2086.md

@@ -1,44 +1,65 @@
 #Double quote to prevent globbing and word splitting.
 
 ### Problematic code:
+
+```sh
 echo $1
+for i in $*; do :; done
+for i in $@; do :; done
+```
 
 ### Correct code:
-    echo "$1"
 
+```sh
+echo "$1"
+for i in "$@"; do :; done # or, 'for i; do'
+```
 ### Rationale
-The problematic code looks like "print the first argument". It's actually "Split the first argument by spaces, tabs and line feeds. Expand each of them as if it was a glob. Join all the resulting strings and filenames with spaces. Print the result."
+
+The first code looks like "print the first argument". It's actually "Split the first argument by IFS (spaces, tabs and line feeds). Expand each of them as if it was a glob. Join all the resulting strings and filenames with spaces. Print the result."
+
+The second one looks like "iterate through all arguments". It's actually "join all the arguments by the first character of IFS (space), split them by IFS and expand each of them as globs, and iterate on the resulting list". The third one skips the joining part.
 
 Quoting variables prevents word splitting and glob expansion, and prevents the script from breaking when input contains spaces, line feeds, glob characters and such.
 
 Strictly speaking, only expansions themselves need to be quoted, but for stylistic reasons, entire arguments with multiple variable and literal parts are often quoted as one:
 
+```sh
     $HOME/$dir/dist/bin/$file        # Unquoted (bad)
     "$HOME"/"$dir"/dist/bin/"$file"  # Minimal quoting (good)
     "$HOME/$dir/dist/bin/$file"      # Canonical quoting (good)
+```
 
 When quoting composite arguments, make sure to exclude globs and brace expansions, which lose their special meaning in double quotes: `"$HOME/$dir/src/*.c"` will not expand, but `"$HOME/$dir/src"/*.c` will.
 
 Note that `$( )` starts a new context, and variables in it have to be quoted independently:
 
+```sh
     echo "This $variable is quoted $(but this $variable is not)"
     echo "This $variable is quoted $(and now this "$variable" is too)"
+```sh
 
 ### Exceptions
 Sometimes you want to split on spaces, like when building a command line.
 
+```sh
     options="-j 5 -B"
     make $options file
+```
 
-Just quoting this doesn't work. Instead, you should have used an array (bash, ksh):
+Just quoting this doesn't work. Instead, you should have used an array (bash, ksh, zsh):
 
-    options=(-j 5 -B)
+```bash
+    options=(-j 5 -B) # ksh: set -A options -- -j 5 -B
     make "${options[@]}" file
+```
 
 or a function (POSIX):
 
+```sh
     make_with_flags() { make -j 5 -B "$@"; }
     make_with_flags file
+```
 
 To split on spaces but not perform glob expansion, Posix has a `set -f` to disable globbing.  You can disable word splitting by setting IFS="".