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$_ in bash vs. dash scripts – Debian

I need to port a short script from bash to dash (i.e. sh under Debian 10). It contains the following line:

chown root:www-data /etc/nginx/conf.d && chmod 775 $_

This now fails because $_ held the previous command’s last argument (i.e. /etc/nginx/conf.d) with bash but now holds a different value with non-interactive dash. As another case in point, outputs from bash -c 'echo 1 2 && echo $_' and dash -c 'echo 1 2 && echo $_' also differ.

What is a typical way for forming "concise" statements of the above type in dash (without resorting to more specialized commands, such as install)?

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2

Answers


  1. 0

    Just write a function.

    chownmod () { chown "$1" "$3" && chmod "$2" "$3"; }

    And replace the line with the following.

    chownmod root:www-data 775 /etc/nginx/conf.d
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  2. 0

    Just define an explicit variable to hold the directory name.

    d=/etc/nginx/conf.d
chown root:www-data "$d" && chmod 755 "$d"

    $_ is intended as an interactive shortcut. A script, written with the help of an editor, doesn’t really need such shortcuts.

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