POSIX shell escaping demo-sheet

shellescaping.sh

#!/bin/sh
# shell escaping "demo-sheet"
# "args" just prints argv[]

filename="/tmp/some file"
echo 'foo echo some file contents' > "$filename"

set -x

args $(echo foo echo wrong)
# + echo foo echo wrong
# + args foo echo wrong
# [1]: "foo"
# [2]: "echo"
# [3]: "wrong"
args "$(echo foo echo better)"
# + echo foo echo better
# + args foo echo better
# [1]: "foo echo better"

args $(cat $filename)
# + cat /tmp/some file
# cat: /tmp/some: No such file or directory
# cat: file: No such file or directory
# + args
args $(cat "$filename")
# + cat /tmp/some file
# + args foo echo some file contents
# [1]: "foo"
# [2]: "echo"
# [3]: "some"
# [4]: "file"
# [5]: "contents"
args "$(cat "$filename")"
# + cat /tmp/some file
# + args foo echo some file contents
# [1]: "foo echo some file contents"
args "$(cat \"$filename\")"
# + cat "/tmp/some file"
# cat: '"/tmp/some': No such file or directory
# cat: 'file"': No such file or directory
# + args
# [1]: ""

args `cat $filename`
# + cat /tmp/some file
# cat: /tmp/some: No such file or directory
# cat: file: No such file or directory
# + args
args `cat "$filename"`
# + cat /tmp/some file
# + args foo echo some file contents
# [1]: "foo"
# [2]: "echo"
# [3]: "some"
# [4]: "file"
# [5]: "contents"
args "`cat "$filename"`"
# + cat /tmp/some file
# + args foo echo some file contents
# [1]: "foo echo some file contents"
args "`cat \"$filename\"`"
# + cat /tmp/some file
# + args foo echo some file contents
# [1]: "foo echo some file contents"

rm "$filename"