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.

Opam 1.1.1                                                                                        OPAM-SWITCH(1)