Environment Variables

    The environment variables that Julia uses generally start with JULIA. If is called with the keyword verbose=true, then the output will list any defined environment variables relevant for Julia, including those which include JULIA in their names.

    Note

    Some variables, such as JULIA_NUM_THREADS and JULIA_PROJECT, need to be set before Julia starts, therefore adding these to ~/.julia/config/startup.jl is too late in the startup process. In Bash, environment variables can either be set manually by running, e.g., export JULIA_NUM_THREADS=4 before starting Julia, or by adding the same command to ~/.bashrc or ~/.bash_profile to set the variable each time Bash is started.

    The absolute path of the directory containing the Julia executable, which sets the global variable Sys.BINDIR. If $JULIA_BINDIR is not set, then Julia determines the value Sys.BINDIR at run-time.

    The executable itself is one of

    by default.

    The global variable Base.DATAROOTDIR determines a relative path from Sys.BINDIR to the data directory associated with Julia. Then the path

    1. $JULIA_BINDIR/$DATAROOTDIR/julia/base

    determines the directory in which Julia initially searches for source files (via Base.find_source_file()).

    Likewise, the global variable Base.SYSCONFDIR determines a relative path to the configuration file directory. Then Julia searches for a startup.jl file at

    by default (via Base.load_julia_startup()).

    For example, a Linux installation with a Julia executable located at /bin/julia, a DATAROOTDIR of ../share, and a SYSCONFDIR of ../etc will have JULIA_BINDIR set to /bin, a source-file search path of

    1. /share/julia/base

    and a global configuration search path of

    JULIA_PROJECT

    A directory path that indicates which project should be the initial active project. Setting this environment variable has the same effect as specifying the --project start-up option, but --project has higher precedence. If the variable is set to @. then Julia tries to find a project directory that contains Project.toml or JuliaProject.toml file from the current directory and its parents. See also the chapter on .

    Note

    JULIA_PROJECT must be defined before starting julia; defining it in startup.jl is too late in the startup process.

    The JULIA_LOAD_PATH environment variable is used to populate the global Julia LOAD_PATH variable, which determines which packages can be loaded via import and using (see ).

    Unlike the shell PATH variable, empty entries in JULIA_LOAD_PATH are expanded to the default value of LOAD_PATH, ["@", "@v#.#", "@stdlib"] when populating LOAD_PATH. This allows easy appending, prepending, etc. of the load path value in shell scripts regardless of whether JULIA_LOAD_PATH is already set or not. For example, to prepend the directory /foo/bar to LOAD_PATH just do

    1. export JULIA_LOAD_PATH="/foo/bar:$JULIA_LOAD_PATH"

    If the JULIA_LOAD_PATH environment variable is already set, its old value will be prepended with . On the other hand, if JULIA_LOAD_PATH is not set, then it will be set to /foo/bar: which will expand to a LOAD_PATH value of ["/foo/bar", "@", "@v#.#", "@stdlib"]. If JULIA_LOAD_PATH is set to the empty string, it expands to an empty LOAD_PATH array. In other words, the empty string is interpreted as a zero-element array, not a one-element array of the empty string. This behavior was chosen so that it would be possible to set an empty load path via the environment variable. If you want the default load path, either unset the environment variable or if it must have a value, set it to the string :.

    The JULIA_DEPOT_PATH environment variable is used to populate the global Julia DEPOT_PATH variable, which controls where the package manager, as well as Julia’s code loading mechanisms, look for package registries, installed packages, named environments, repo clones, cached compiled package images, configuration files, and the default location of the REPL’s history file.

    If the JULIA_DEPOT_PATH environment variable is already set, its old value will be prepended with /foo/bar. On the other hand, if JULIA_DEPOT_PATH is not set, then it will be set to /foo/bar: which will have the effect of prepending /foo/bar to the default depot path. If JULIA_DEPOT_PATH is set to the empty string, it expands to an empty DEPOT_PATH array. In other words, the empty string is interpreted as a zero-element array, not a one-element array of the empty string. This behavior was chosen so that it would be possible to set an empty depot path via the environment variable. If you want the default depot path, either unset the environment variable or if it must have a value, set it to the string :.

    Note

    On Windows, path elements are separated by the ; character, as is the case with most path lists on Windows.

    JULIA_HISTORY

    The absolute path REPL.find_hist_file() of the REPL’s history file. If $JULIA_HISTORY is not set, then REPL.find_hist_file() defaults to

    1. $(DEPOT_PATH[1])/logs/repl_history.jl

    JULIA_SHELL

    The absolute path of the shell with which Julia should execute external commands (via Base.repl_cmd()). Defaults to the environment variable $SHELL, and falls back to /bin/sh if $SHELL is unset.

    Note

    On Windows, this environment variable is ignored, and external commands are executed directly.

    JULIA_EDITOR

    The editor returned by InteractiveUtils.editor() and used in, e.g., , referring to the command of the preferred editor, for instance vim.

    $JULIA_EDITOR takes precedence over $VISUAL, which in turn takes precedence over $EDITOR. If none of these environment variables is set, then the editor is taken to be open on Windows and OS X, or /etc/alternatives/editor if it exists, or emacs otherwise.

    Overrides the global variable Base.Sys.CPU_THREADS, the number of logical CPU cores available.

    A that sets the value of Distributed.worker_timeout() (default: 60.0). This function gives the number of seconds a worker process will wait for a master process to establish a connection before dying.

    An unsigned 64-bit integer (uint64_t) that sets the maximum number of threads available to Julia. If $JULIA_NUM_THREADS is not positive or is not set, or if the number of CPU threads cannot be determined through system calls, then the number of threads is set to 1.

    Note

    JULIA_NUM_THREADS must be defined before starting julia; defining it in startup.jl is too late in the startup process.

    Julia 1.5

    In Julia 1.5 and above the number of threads can also be specified on startup using the -t/--threads command line argument.

    If set to a string that starts with the case-insensitive substring "infinite", then spinning threads never sleep. Otherwise, is interpreted as an unsigned 64-bit integer (uint64_t) and gives, in nanoseconds, the amount of time after which spinning threads should sleep.

    If set to anything besides 0, then Julia’s thread policy is consistent with running on a dedicated machine: the master thread is on proc 0, and threads are affinitized. Otherwise, Julia lets the operating system handle thread policy.

    Environment variables that determine how REPL output should be formatted at the terminal. Generally, these variables should be set to ANSI terminal escape sequences. Julia provides a high-level interface with much of the same functionality; see the section on .

    The formatting Base.warn_color() (default: yellow, "\033[93m") that warnings should have at the terminal.

    The formatting Base.info_color() (default: cyan, "\033[36m") that info should have at the terminal.

    The formatting Base.input_color() (default: normal, "\033[0m") that input should have at the terminal.

    The formatting Base.answer_color() (default: normal, "\033[0m") that output should have at the terminal.

    Enable debug logging for a file or module, see Logging for more information.

    JULIA_GC_ALLOC_POOL, JULIA_GC_ALLOC_OTHER, JULIA_GC_ALLOC_PRINT

    If set, these environment variables take strings that optionally start with the character 'r', followed by a string interpolation of a colon-separated list of three signed 64-bit integers (int64_t). This triple of integers a:b:c represents the arithmetic sequence a, a + b, a + 2*b, … c.

    • If it’s the nth time that jl_gc_pool_alloc() has been called, and n belongs to the arithmetic sequence represented by $JULIA_GC_ALLOC_POOL, then garbage collection is forced.
    • If it’s the nth time that maybe_collect() has been called, and n belongs to the arithmetic sequence represented by $JULIA_GC_ALLOC_OTHER, then garbage collection is forced.
    • If it’s the nth time that jl_gc_collect() has been called, and n belongs to the arithmetic sequence represented by $JULIA_GC_ALLOC_PRINT, then counts for the number of calls to jl_gc_pool_alloc() and maybe_collect() are printed.

    If the value of the environment variable begins with the character 'r', then the interval between garbage collection events is randomized.

    Note

    These environment variables only have an effect if Julia was compiled with garbage-collection debugging (that is, if WITH_GC_DEBUG_ENV is set to 1 in the build configuration).

    JULIA_GC_NO_GENERATIONAL

    If set to anything besides 0, then the Julia garbage collector never performs “quick sweeps” of memory.

    Note

    This environment variable only has an effect if Julia was compiled with garbage-collection debugging (that is, if WITH_GC_DEBUG_ENV is set to 1 in the build configuration).

    JULIA_GC_WAIT_FOR_DEBUGGER

    If set to anything besides 0, then the Julia garbage collector will wait for a debugger to attach instead of aborting whenever there’s a critical error.

    Note

    This environment variable only has an effect if Julia was compiled with garbage-collection debugging (that is, if WITH_GC_DEBUG_ENV is set to 1 in the build configuration).

    ENABLE_JITPROFILING

    If set to anything besides 0, then the compiler will create and register an event listener for just-in-time (JIT) profiling.

    Note

    This environment variable only has an effect if Julia was compiled with JIT profiling support, using either

    • Intel’s (USE_INTEL_JITEVENTS set to 1 in the build configuration), or
    • OProfile (USE_OPROFILE_JITEVENTS set to 1 in the build configuration).

    ENABLE_GDBLISTENER

    If set to anything besides 0 enables GDB registration of Julia code on release builds. On debug builds of Julia this is always enabled. Recommended to use with .

    JULIA_LLVM_ARGS