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I am trying to decrypt a file in a script with gpg batch mode, but command is not executed because the passphrase contains a "!"

echo "m!pass"|gpg --batch --passphrase-fd 0 --decrypt-file plain.gpg
bash: !pass": event not found

or

gpg --batch --passphrase "m!pass" -d plain.gpg 
bash: !pass": event not found

I guess bash is interpreting the exclamation mark as a reference to the command execution history. Which would be the right way to do it in GPG batch mode?

2 Answers 2

6

Use single quotes instead of double:

$ echo "m!pass"
bash: !pass": event not found
$ echo 'm!pass'
m!pass

This is quite nicely explained in the bash manual (emphasis added):

Single Quotes

Enclosing characters in single quotes (‘'’) preserves the literal value of each character within the quotes. A single quote may not occur between single quotes, even when preceded by a backslash.

Double Quotes

Enclosing characters in double quotes (‘"’) preserves the literal value of all characters within the quotes, with the exception of ‘$’, ‘’, ‘\’, and, when history expansion is enabled, ‘!’. The characters ‘$’ and ‘’ retain their special meaning within double quotes (see Shell Expansions). The backslash retains its special meaning only when followed by one of the following characters: ‘$’, ‘`’, ‘"’, ‘\’, or newline. Within double quotes, backslashes that are followed by one of these characters are removed. Backslashes preceding characters without a special meaning are left unmodified. A double quote may be quoted within double quotes by preceding it with a backslash. If enabled, history expansion will be performed unless an ‘!’ appearing in double quotes is escaped using a backslash. The backslash preceding the ‘!’ is not removed.

1

My preferred method is to just disable the stupid history expansion feature you never heard of and never wanted and will likely never use even though you now know about it:

$ echo "hello!"
bash: !": event not found

$ set +o histexpand

$ echo "hello!"
hello!

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