NAME

       opam-switch - Manage multiple installation of compilers.

SYNOPSIS

       opam switch [OPTION]... [COMMAND] [ARG]...

DESCRIPTION

       This command allows one to switch between different compiler versions, installing the
       compiler if opam switch is used to switch to that compiler for the first time. The
       different compiler versions are totally independent from each other, meaning that OPAM
       maintains a separate state (e.g. list of installed packages...) for each.

       See the documentation of opam switch list to see the compilers which are available, and
       how to switch or to install a new one.

ARGUMENTS

       COMMAND
           Name of the sub-command. See the COMMANDS section for more info. If a compiler switch
           is given instead of an usual command, this command will switch to the given compiler.
           You will then need to run eval `opam config env` to update your environment variables.

OPTIONS

       -A COMP, --alias-of=COMP
           The name of the compiler description which will be aliased.

       -a, --all
           List all the compilers which can be installed on the system.

       -b, --keep-build-dir
           Keep the build directory. This is equivalent to setting $OPAMKEEPBUILDIR to a
           non-empty string.

       --cudf=FILENAME
           Save the CUDF request sent to the solver to FILENAME-<n>.cudf.

       -d, --build-doc
           Build the package documentation. This is equivalent to setting $OPAMBUILDDOC to a
           non-empty string.

       --dry-run
           Simply call the solver without actually performing any build/install operations.

       -e TAGS, --external=TAGS
           Display the external packages associated to the given tags.

       -f FILENAME, --filename=FILENAME
           The name of the file to export to/import from.

       --fake
           WARNING: This option is for testing purposes only! Using this option without care is
           the best way to corrupt your current compiler environment. When using this option OPAM
           will run a dry-run of the solver and then fake the build and install commands.

       -i, --installed
           List installed compiler switches only.

       -j JOBS, --jobs=JOBS
           Set the maximal number of concurrent jobs to use. You can also set it using the
           OPAMJOBS environment variable.

       --json=FILENAME
           Save the result output of an OPAM run in a computer-readable file

       -m MAKE, --make=MAKE
           Use MAKE as the default 'make' command.

       --no-checksums
           Do not verify the checksum of downloaded archives.This is equivalent to setting
           $OPAMNOCHECKSUMS to a non-empty string.

       --no-switch
           Only install the compiler switch, without switching to it. If the compiler switch is
           already installed, then do nothing.

       --no-warning
           Do not display any warning related to environment variables.

       -s, --short
           Output the names separated by one whitespace instead of using the usual formatting.

       -t, --build-test
           Build and run the package unit-tests. This is equivalent to setting $OPAMBUILDTEST to
           a non-empty string.

COMMANDS

       install
           Install the given compiler. The commands fails if the package is already installed
           (e.g. it will not transparently switch to the installed compiler switch, as opam
           switch <name> does).

       remove
           Remove the given compiler.

       export
           Export the list installed package to a file.

       import
           Install the packages from a file.

       reinstall
           Reinstall the given compiler switch. This will also try reinstall the installed
           packages.

       list
           List compilers. By default, lists installed and `standard' compilers. Use `--all' to
           get the list of all installable compilers. The first column displays the switch name
           (if any), the second one the switch state (C = current, I = installed, -- = not
           installed), the third one the compiler name and the last one the compiler description.
           To switch to an already installed compiler alias (with state = I), use opam switch
           <name>. If you want to use a new compiler <comp>, use opam switch <comp>: this will
           download, compile and create a fresh and independent environment where new packages
           can be installed. If you want to create a new compiler alias (for instance because you
           already have this compiler version installed), use opam switch <name> --alias-of
           <comp>. In case <name> and <comp> are the same, this is equivalent to opam switch
           <comp>.

       show
           Show the current compiler.

COMMON OPTIONS

       These options are common to all commands.

       --color=WHEN (absent=auto)
           Colorize the output. WHEN must be `always', `never' or `auto'.

       --compat-mode-1.0
           Compatibility mode with OPAM 1.0

       --debug
           Print debug message on stdout. This is equivalent to setting $OPAMDEBUG to a non-empty
           value.

       --git-version
           Print the git version if it exists and exit.

       --help[=FMT] (default=pager)
           Show this help in format FMT (pager, plain or groff).

       --no-aspcud
           Do not use the external aspcud solver, even if available.

       --no-base-packages
           Do not install base packages (useful for testing purposes). This is equivalent to
           setting $OPAMNOBASEPACKAGES to a non-empty string.

       -q, --quiet
           Be quiet when installing a new compiler.

       -r ROOT, --root=ROOT (absent=~/.opam)
           Use ROOT as the current root path. This is equivalent to setting $OPAMROOT to ROOT.

       --strict
           Fail whenever an error is found in a package definition or a configuration file. The
           default is to continue silently if possible.

       --switch=SWITCH
           Use SWITCH as the current compiler switch. This is equivalent to setting $OPAMSWITCH
           to SWITCH.

       -v, --verbose
           Be more verbose. This is equivalent to setting $OPAMVERBOSE to a non-empty value.

       --version
           Show version information.

       -y, --yes
           Disable interactive mode and answer yes to all questions that would otherwise be asked
           to the user. This is equivalent to setting $OPAMYES to a non-empty string.

ENVIRONMENT VARIABLES

       opam makes use of environment variables listed here.

       OPAMCOLOR, when set to always or never, sets a default value for the --color option

       OPAMCURL can be used to define an alternative for the 'curl' command-line utility to
       download files

FURTHER DOCUMENTATION

       See https://opam.ocaml.org.

AUTHORS

       Thomas Gazagnaire <thomas@gazagnaire.org>
       Anil Madhavapeddy <anil@recoil.org>
       Fabrice Le Fessant <Fabrice.Le_fessant@inria.fr>
       Frederic Tuong <tuong@users.gforge.inria.fr>
       Louis Gesbert <louis.gesbert@ocamlpro.com>
       Vincent Bernardoff <vb@luminar.eu.org>
       Guillem Rieu <guillem.rieu@ocamlpro.com>

BUGS

       Check bug reports at https://github.com/OCamlPro/opam/issues.