If both a variable name and values are provided, ``set`` assigns the values to the variable of that name. Because all variables in fish are :ref:`lists <variables-lists>`, multiple values are allowed.
If ``set`` is called with no arguments, it prints the names and values of all shell variables in sorted order. Passing :ref:`scope <variables-scope>` or :ref:`export <variables-export>` flags allows filtering this to only matching variables, so ``set --local`` would only show local variables.
-``-l`` or ``--local`` scopes the variable to the currently executing block. It is erased when the block ends. Outside of a block, this is the same as ``--function``.
-``-g`` or ``--global`` causes the specified shell variable to be given a global scope. Global variables don't disappear and are available to all functions running in the same shell. They can even be modified.
-``-U`` or ``--universal`` causes the specified shell variable to be given a universal scope. If this option is supplied, the variable will be shared between all the current user's fish instances on the current computer, and will be preserved across restarts of the shell.
-``--path`` causes the specified variable to be treated as a path variable, meaning it will automatically be split on colons, and joined using colons when quoted (``echo "$PATH"``) or exported.
-``--unpath`` causes the specified variable to not be treated as a path variable. Variables with a name ending in "PATH" are automatically path variables, so this can be used to treat such a variable normally.
-``-a`` or ``--append`` causes the values to be appended to the current set of values for the variable. This can be used with ``--prepend`` to both append and prepend at the same time. This cannot be used when assigning to a variable slice.
-``-p`` or ``--prepend`` causes the values to be prepended to the current set of values for the variable. This can be used with ``--append`` to both append and prepend at the same time. This cannot be used when assigning to a variable slice.
-``-q`` or ``--query`` test if the specified variable names are defined. Does not output anything, but the builtins exit status is the number of variables specified that were not defined, up to a maximum of 255. If no variable was given, it also returns 255.
-``-S`` or ``--show`` shows information about the given variables. If no variable names are given then all variables are shown in sorted order. It shows the scopes the given variables are set in, along with the values in each and whether or not it is exported. No other flags can be used with this option.
If a variable is set to more than one value, the variable will be a list with the specified elements. If a variable is set to zero elements, it will become a list with zero elements.
If the variable name is one or more list elements, such as ``PATH[1 3 7]``, only those list elements specified will be changed. If you specify a negative index when expanding or assigning to a list variable, the index will be calculated from the end of the list. For example, the index -1 means the last index of a list.
- If a variable is not explicitly set to be either universal, global or local and has never before been defined, the variable will be local to the currently executing function. Note that this is different from using the ``-l`` or ``--local`` flag. If one of those flags is used, the variable will be local to the most inner currently executing block, while without these the variable will be local to the function. If no function is executing, the variable will be global.
- If a variable is not explicitly set to be exported or not exported, but has been previously defined, the previous exporting rule for the variable is kept.
``set`` requires all options to come before any other arguments. For example, ``set flags -l`` will have the effect of setting the value of the variable ``flags`` to '-l', not making the variable local.
In assignment mode, ``set`` does not modify the exit status, but passes along whatever $status was set, including by command substitutions. This allows capturing the output and exit status of a subcommand, like in ``if set output (command)``.
In query mode, the exit status is the number of variables that were not found.
In erase mode, ``set`` exits with a zero exit status in case of success, with a non-zero exit status if the commandline was invalid, if any of the variables did not exist or was a :ref:`special read-only variable <variables-special>`.
