How can I check the verbatim characters of a bash command string?

You could use cat with the -A option: from the manual:

   -A, --show-all
          equivalent to -vET
   -E, --show-ends
          display $ at end of each line
   -T, --show-tabs
          display TAB characters as ^I
   -v, --show-nonprinting
          use ^ and M- notation, except for LFD and TAB

So cat -A yourscrip.sh will show you invisible and strange characters.

One option is to look at the characters you're trying to use with a hex viewer or editor. hexdump is a good option if you are limited to the terminal.

$ hexdump -Cv <<"EOF"
> [ -f /etc/openvpn/client.conf ] && echo true
> EOF
00000000  5b 20 2d 66 20 2f 65 74  63 2f 6f 70 65 6e 76 70  |[ -f /etc/openvp|
00000010  6e 2f 63 6c 69 65 6e 74  2e 63 6f 6e 66 20 5d 20  |n/client.conf ] |
00000020  26 26 20 65 63 68 6f 20  74 72 75 65 0a           |&& echo true.|
0000002d

You can see here that the space, close-square-brace, space are correct - 0x20, 0x5D, 0x20.

These values are ASCII codes, displayed in hexadecimal. Any value outside the range 0x20 - 0x7E is not a "printable character" as far as ASCII is concerned, and most likely won't play well with command line interfaces.

Note: I copied your first "broken" line for use in the hexdump example above, so something has replaced the not-an-ASCII-space with an ASCII space between your original source and your rendered question.

---

To repeat this, take the following steps:

1. Type hexdump -Cv <<"EOF" and press Enter
2. Paste the text you would like to use
3. Type EOF on a line of its own, and press Enter

---

Terminals and Command Line Interfaces don't handle special characters well - as you have discovered. If you aren't very careful with formatting documents, you will also have problems with Microsoft Word (and others) using "smart quotes", em-dashes, the list goes on...

Spot the difference: (the top is "smart quotes", the bottom is "straight quotes")

$ hexdump -Cv <<"EOF"
> “quoted string”
> EOF
00000000  e2 80 9c 71 75 6f 74 65  64 20 73 74 72 69 6e 67  |...quoted string|
00000010  e2 80 9d 0a                                       |....|
00000014

Here, the open quotes are not a simple ASCII quote ("), but are a Unicode / UTF-8 series - 0xE2, 0x80, 0x9C, or U+201C - which the terminal will not handle as you might expect.

Kiwy's suggestion of cat -A also does the job:

$ cat -A <<"EOF"
> “quoted string”
> EOF
M-bM-^@M-^\quoted stringM-bM-^@M-^]$

---

Note: when using echo "..." | hd, you stand a chance that bash will substitute parts of the string you are trying to inspect. This is particularly of concern when trying to inspect components of a script.

For example try:

$ echo "${USER}"
attie

$ echo "`whoami`"
attie

$ echo "$(whoami)"
attie

$ cat <<EOF
> ${USER}
> EOF
attie

These methods are replacing components with the relevant text. To avoid this, use one of the following approaches. Note the use of single quotes ('), and a "quoted heredoc" ("EOF").

$ echo '${USER}'
${USER}

$ echo '`whoami`'
`whoami`

$ echo '$(whoami)'
$(whoami)

$ cat <<"EOF"
> ${USER}
> EOF
${USER}

echo "<your command>" | hd should work. Look for backspace (0x08) or characters with codes >=80. echo "<your command>" | wc -b and checking that the count matches what you see is also a good idea.

Copying stuff from files produced by anything with "Office" in its name is dangerous, because such software often takes the liberty to replace characters: in French, look out for double quotes replaced by "guillemets", in English for plain quotes replaced by their open/close equivalents. The hardest one I ever found was a 0-width non-breaking space in the middle of a file name (3 days of server downtime...).