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Ubuntu – How to deal with special characters in linux passwords

I am running the following command:

echo 'my!#%^password' | sudo -S bash -c 'useradd -m -s /usr/sbin/nologin -p $(echo my!#%^password | openssl passwd -1 -stdin) george'

The issue I am having is the special characters. Some break the command, like !@& which seem to be the issue. Is there a way to run the same command to allow any special characters?

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  1. Chosen as BEST ANSWER
    0

    When creating Linux passwords, the following non-alphanumeric characters need to be escaped in the shell because they have special meanings:

    • ! (exclamation mark): In many shells, this is used for history substitution.
    • $ (dollar sign): This is used to denote variables.
    • & (ampersand): This is used to run a command in the background.
    • * (asterisk): This is used as a wildcard for file matching.
    • ? (question mark): This is also used as a wildcard for file matching.
    • " (double quote): This is used to define strings, and within them variable and command substitution is performed.
    • ' (single quote): This is used to define strings, and within them no substitution is performed.
    • (backslash): This is used to escape characters that have special meaning.
    • | (pipe): This is used to pipe the output of one command to another.
    • ; (semicolon): This is used to separate multiple commands.
    • (, ) (parentheses): These are used to create subshells.
    • <, > (less than, greater than): These are used for input and output redirection.
    • {, } (curly braces): These are used in parameter expansion and for executing commands in the current shell context.
    • [, ] (square brackets): These are used in pattern matching and array indexing.
    • # (hash): This is used for comments.
    • ~ (tilde): This is used for home directory substitution.
    • ^ (caret): In some shells, this is used for history substitution or pattern removal.
    • (space): This is used to separate items and commands.
    • n (newline), r (carriage return), t (tab): These are whitespace characters that can cause issues in passwords.

    Remember, it's not that you can't use these characters in passwords, but if you're entering a password in the shell (for example, in a script), you would need to escape these characters to prevent them from being interpreted by the shell.


  2. 0

    You can "escape" those special characters by using backslash. This character:

    Those characters that are breaking the command need to be preceded by a backslash. Otherwise they are interpreted as Regular Expression characters.

    e.g.

    echo my!#%^password
becomes
echo my!#%^password

    I might have missed some but the CLI output should tell you if you’ve missed them.

    Edit: apparently the user interface for stack overflow interprets those backslash characters and removes them. I’ve surrounded the example in code format.

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