set - display and change shell variables¶
set [SCOPE_OPTIONS] set [OPTIONS] VARIABLE VALUES ... set [OPTIONS] VARIABLE[INDICES] VALUES ... set (-q | --query) [SCOPE_OPTIONS] VARIABLE ... set (-e | --erase) [SCOPE_OPTIONS] VARIABLE ... set (-e | --erase) [SCOPE_OPTIONS] VARIABLE[INDICES] ... set (-S | --show) VARIABLE ...
set manipulates shell variables.
If both a VARIABLE and VALUES are provided,
set assigns the values to the variable of that name. Because all variables in fish are lists, multiple values are allowed.
If only a variable name has been given,
set sets the variable to the empty list.
set is called with no arguments, it prints the names and values of all shell variables in sorted order. Passing scope or export flags allows filtering this to only matching variables, so
set --local would only show local variables.
--erase and optionally a scope flag
set will erase the matching variable (or the variable of that name in the smallest possible scope).
set will describe the given variable names, explaining how they have been defined - in which scope with which values and options.
The following options control variable scope:
- -f or --function
Scopes the variable to the currently executing function. It is erased when the function ends.
- -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.
These options control additional variable options:
- -x or --export
Causes the specified shell variable to be exported to child processes (making it an “environment variable”)
- -u or --unexport
Causes the specified shell variable to NOT be exported to child processes
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.
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.
The following other options are available:
- -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.
- -e or --erase
Causes the specified shell variables to be erased
- -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.
- -n or --names
List only the names of all defined variables, not their value. The names are guaranteed to be sorted.
- -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.
- -L or --long
Do not abbreviate long values when printing set variables.
- -h or --help
Displays help about using this command.
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.
The scoping rules when creating or updating a variable are:
Variables may be explicitly set to universal, global or local. Variables with the same name in different scopes will not be changed.
If a variable is not explicitly set to be either universal, global or local, but has been previously defined, the previous variable scope is used.
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
--localflag. 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.
The exporting rules when creating or updating a variable are identical to the scoping rules for variables:
Variables may be explicitly set to either exported or not exported. When an exported variable goes out of scope, it is unexported.
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.
If a variable is not explicitly set to be either exported or unexported and has never before been defined, the variable will not be exported.
In query mode, the scope to be examined can be specified. Whether the variable has to be a path variable or exported can also be specified.
In erase mode, if variable indices are specified, only the specified slices of the list variable will be erased.
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 special read-only variable.
# Prints all global, exported variables. set -xg # Sets the value of the variable $foo to be 'hi'. set foo hi # Appends the value "there" to the variable $foo. set -a foo there # Does the same thing as the previous two commands the way it would be done pre-fish 3.0. set foo hi set foo $foo there # Removes the variable $smurf set -e smurf # Changes the fourth element of the $PATH list to ~/bin set PATH ~/bin # Outputs the path to Python if ``type -p`` returns true. if set python_path (type -p python) echo "Python is at $python_path" end # Setting a variable doesn't modify $status! false set foo bar echo $status # prints 1, because of the "false" above. true set foo banana (false) echo $status # prints 1, because of the "(false)" above. # Like other shells, pass a variable to just one command: # Run fish with a temporary home directory. HOME=(mktemp -d) fish # Which is essentially the same as: begin; set -lx HOME (mktemp -d); fish; end
Fish versions prior to 3.0 supported the syntax
set PATH PATH /bin /sbin, which worked like
set PATH[1 4] /bin /sbin. This syntax was not widely used, and was ambiguous and inconsistent.