Provided by: opam-doc_2.0.3-1_all bug


       opam-switch - Manage multiple installation prefixes.


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


       This command is used to manage "switches", which are independent installation prefixes
       with their own compiler and sets of installed and pinned packages. This is typically
       useful to have different versions of the compiler available at once.

       Use opam switch create to create a new switch, and opam switch set to set the currently
       active switch. Without argument, lists installed switches, with one switch argument,
       defaults to set.

       Switch handles SWITCH can be either a plain name, for switches that will be held inside
       ~/.opam, or a directory name, which in that case is the directory where the switch prefix
       will be installed, as _opam. Opam will automatically select a switch by that name found in
       the current directory or its parents, unless OPAMSWITCH is set or --switch is specified.
       When creating a directory switch, if package definitions are found locally, the user is
       automatically prompted to install them after the switch is created unless --no-install is

       opam switch set sets the default switch globally, but it is also possible to select a
       switch in a given shell session, using the environment. For that, use eval $(opam env
       --switch=SWITCH --set-switch).


       Without argument, defaults to list.

           With a SWITCH argument, defaults to set SWITCH.

       create SWITCH [COMPILER]
           Create a new switch, and install the given compiler there. SWITCH can be a plain name,
           or a directory, absolute or relative, in which case a local switch is created below
           the given directory. COMPILER, if omitted, defaults to SWITCH if it is a plain name,
           unless --packages or --empty is specified. When creating a local switch, and none of
           these options are present, the compiler is chosen according to the configuration
           default (see opam-init(1)). If the chosen directory contains package definitions, a
           compatible compiler is searched within the default selection, and the packages will
           automatically get installed.

       set SWITCH
           Set the currently active switch, among the installed switches.

       remove SWITCH
           Remove the given switch from disk.

       export FILE
           Save the current switch state to a file. If --full is specified, it includes the
           metadata of all installed packages

       import FILE
           Import a saved switch state. If --switch is specified and doesn't point to an existing
           switch, the switch will be created for the import.

       reinstall [SWITCH]
           Reinstall the given compiler switch and all its packages.

           Lists installed switches.

       list-available [PATTERN]
           Lists base packages that can be used to create a new switch, i.e. packages with the
           compiler flag set. If no pattern is supplied, all versions are shown.

           Prints the name of the current switch.

       set-base PACKAGES
           Sets the packages forming the immutable base for the selected switch, overriding the
           current setting.

       set-description STRING
           Sets the description for the selected switch

       link SWITCH [DIR]
           Sets a local alias for a given switch, so that the switch gets automatically selected
           whenever in that directory or a descendant.

       install SWITCH
           Deprecated alias for 'create'.


       -A COMP, --alias-of=COMP
           This option is deprecated.

           When creating a local switch in a project directory (i.e. a directory containing opam
           package definitions), install the dependencies of the project but not the project

           Attach the given description to a switch when creating it. Use the set-description
           subcommand to modify the description of an existing switch.

           Allow creating an empty (without compiler) switch.

           When exporting, include the metadata of all installed packages, allowing to re-import
           even if they don't exist in the repositories (the default is to include only the
           metadata of pinned packages).

       -j JOBS, --jobs=JOBS
           Set the maximal number of concurrent jobs to use. The default value is calculated from
           the number of cores. You can also set it using the $OPAMJOBS environment variable.

           This option is deprecated.

           When creating a local switch, don't look for any local package definitions to install.

           Don't automatically select newly installed switches.

           When installing a switch, explicitly define the set of packages to set as the

           When creating a new switch, use the given selection of repositories instead of the
           default. REPOS should be a comma-separated list of either already registered
           repository names (configured through e.g. opam repository add --dont-select), or
           NAME=URL bindings, in which case NAME should not be registered already to a different
           URL, and the new repository will be registered. See opam repository for more details.
           This option also affects list-available.

       -s, --short
           Output raw lists of names, one per line, skipping any details.


       -b, --keep-build-dir
           Keep the build directories after compiling packages. This is equivalent to setting
           $OPAMKEEPBUILDDIR to "true".

       -d, --with-doc, --build-doc
           Build the package documentation. This only affects packages listed on the
           command-line. The --build-doc form is deprecated as this does also installation. This
           is equivalent to setting $OPAMWITHDOC (or the deprecated $OPAMBUILDDOC) to "true".

           Simulate the command, but don't actually perform any changes. This also can be set
           with environment variable $OPAMDEBUG.

           This option registers the actions into the opam database, without actually performing
           them. WARNING: This option is dangerous and likely to break your opam environment. You
           probably want `--dry-run'. You've been warned.

       --ignore-constraints-on[=PACKAGES] (default=)
           Forces opam to ignore version constraints on all dependencies to the listed packages.
           This can be used to test compatibility, but expect builds to break when using this.
           Note that version constraints on optional dependencies and conflicts are unaffected.
           This is equivalent to setting $OPAMIGNORECONSTRAINTS.

           When compiling a package which has its source bound to a local directory, process the
           build and install actions directly in that directory, rather than in a clean copy
           handled by opam. This only affects packages that are explicitly listed on the
           command-line. This is equivalent to setting $OPAMINPLACEBUILD to "true".

       --locked[=SUFFIX] (default=locked)
           In commands that use opam files found from pinned sources, if a variant of the file
           with an added .SUFFIX extension is found (e.g. foo.opam.locked besides foo.opam), that
           will be used instead. This is typically useful to offer a more specific set of
           dependencies and reproduce similar build contexts, hence the name. The opam lock
           plugin can be used to generate such files, based on the versions of the dependencies
           currently installed on the host. This is equivalent to setting the $OPAMLOCKED
           environment variable. Note that this option doesn't generally affect already pinned

       -m MAKE, --make=MAKE
           Use MAKE as the default 'make' command. Deprecated: use opam config set[-global] make
           MAKE instead. Has no effect if the make variable is defined.

           Do not verify the checksum of downloaded archives.This is equivalent to setting
           $OPAMNOCHECKSUMS to "true".

           Reject the installation of packages that don't provide a checksum for the upstream
           archives. This is equivalent to setting $OPAMREQUIRECHECKSUMS to "true".

           Reuse existing build directories (kept by using --keep-build-dir), instead of
           compiling from a fresh clone of the source. This can be faster, but also lead to
           failures if the build systems of the packages don't handle upgrades of dependencies
           well. This is equivalent to setting $OPAMREUSEBUILDDIR to "true".

           Call the solver and display the actions. Don't perform any changes. This is equivalent
           to setting $OPAMSHOW.

           When running an install, upgrade or reinstall on source-pinned packages, they are
           normally updated from their origin first. This flag disables that behaviour and will
           keep them to their version in cache. This is equivalent to setting $OPAMSKIPUPDATE.

       -t, --with-test, --build-test
           Build and run the package unit-tests. This only affects packages listed on the
           command-line. The --build-test form is deprecated as this also affects installation.
           This is equivalent to setting $OPAMWITHTEST (or the deprecated $OPAMBUILDTEST) to

           Allow changes to the packages set as switch base (typically, the main compiler). Use
           with caution. This is equivalent to setting the $OPAMUNLOCKBASE environment variable


       These options are common to all commands.

           Don't fail if all requested packages can't be installed: try to install as many as
           possible. Note that not all external solvers may support this option (recent versions
           of aspcud or mccs should). This is equivalent to setting $OPAMBESTEFFORT environment

           Colorize the output. WHEN must be one of `always', `never' or `auto'.

           Specify user preferences for dependency solving for this run. Overrides both
           $OPAMCRITERIA and $OPAMUPGRADECRITERIA. For details on the supported language, and the
           external solvers available, see A
           general guide to using solver preferences can be found at

           Debug option: Save the CUDF requests sent to the solver to FILENAME-<n>.cudf.

           Print debug message to stderr. This is equivalent to setting $OPAMDEBUG to "true".

           Like --debug, but allows specifying the debug level (--debug sets it to 1). Equivalent
           to setting $OPAMDEBUG to a positive integer.

           Print the git version of opam, if set (i.e. you are using a development version), and

       --help[=FMT] (default=auto)
           Show this help in format FMT. The value FMT must be one of `auto', `pager', `groff' or
           `plain'. With `auto', the format is `pager` or `plain' whenever the TERM env var is
           `dumb' or undefined.

           Ignore extra pins required by packages that get pinned, either manually through opam
           pin or through opam install DIR. This is equivalent to setting IGNOREPINDEPENDS=true.

           Save the results of the opam run in a computer-readable file. If the filename contains
           the character `%', it will be replaced by an index that doesn't overwrite an existing
           file. Similar to setting the $OPAMJSON variable.


           When configuring or updating a repository that is written for an earlier opam version
           (1.2), opam internally converts it to the current format. This disables this
           behaviour. Note that repositories should define their format version in a 'repo' file
           at their root, or they will be assumed to be in the older format. It is, in any case,
           preferable to upgrade the repositories manually using opam admin upgrade [--mirror
           URL] when possible.

           Opam will replace itself with a newer binary found at OPAMROOT/opam if present. This
           disables this behaviour.

       -q, --quiet
           Disables --verbose.

           Use ROOT as the current root path. This is equivalent to setting $OPAMROOT to ROOT.

       --safe, --readonly
           Make sure nothing will be automatically updated or rewritten. Useful for calling from
           completion scripts, for example. Will fail whenever such an operation is needed ; also
           avoids waiting for locks, skips interactive questions and overrides the $OPAMDEBUG
           variable. This is equivalent to set environment variable $OPAMSAFE.

           Specify the CUDF solver to use for resolving package installation problems. This is
           either a predefined solver (this version of opam supports builtin-dummy-solver,
           aspcud, mccs, aspcud-old, packup), or a custom command that should contain the
           variables %{input}%, %{output}%, %{criteria}%, and optionally %{timeout}%. This is
           equivalent to setting $OPAMEXTERNALSOLVER.

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

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

           Disable any external solver, and use the built-in one (this requires that opam has
           been compiled with a built-in solver). This is equivalent to setting $OPAMNOASPCUD or

       -v, --verbose
           Be more verbose. One -v shows all package commands, repeat to also display commands
           called internally (e.g. tar, curl, patch etc.) Repeating n times is equivalent to
           setting $OPAMVERBOSE to "n".

           Show version information.

       -w, --working-dir
           Whenever updating packages that are bound to a local, version-controlled directory,
           update to the current working state of their source instead of the last committed
           state, or the ref they are pointing to. This only affects packages explicitly listed
           on the command-line.It can also be set with $OPAMWORKINGDIR.

       -y, --yes
           Answer yes to all yes/no questions without prompting. This is equivalent to setting
           $OPAMYES to "true".


       Opam makes use of the environment variables listed here. Boolean variables should be set
       to "0", "no", "false" or the empty string to disable, "1", "yes" or "true" to enable.

       OPAMALLPARENS surround all filters with parenthesis

       OPAMAUTOREMOVE see remove option `--auto-remove`

       OPAMBESTEFFORT see option `--best-effort`

       OPAMBESTEFFORTPREFIXCRITERIA sets the string that must be prepended to the criteria when
       the `--best-effort` option is set, and is expected to maximise the `opam-query` property
       in the solution

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

       OPAMCRITERIA specifies user preferences for dependency solving. The default value depends
       on the solver version, use `config report` to know the current setting. See also option

       OPAMCUDFFILE file save the cudf graph to

       OPAMCURL can be used to select a given 'curl' program. See OPAMFETCH for more options.

       OPAMDEBUG see options `--debug' and `--debug-level'.

       OPAMDOWNLOADJOBS sets the maximum number of simultaneous downloads.

       OPAMDRYRUN see option `--dry-run`

       OPAMEDITOR sets the editor to use for opam file editing, overrides $EDITOR and $VISUAL

       OPAMERRLOGLEN sets the number of log lines printed when a sub-process fails. 0 to print

       OPAMEXTERNALSOLVER see option `--solver'.

       OPAMFAKE see option `--fake`

       OPAMFETCH specifies how to download files: either `wget', `curl' or a custom command where
       variables %{url}%, %{out}%, %{retry}%, %{compress}% and %{checksum}% will be replaced.
       Overrides the 'download-command' value from the main config file.

       OPAMFIXUPCRITERIA same as OPAMUPGRADECRITERIA, but specific to fixup

       OPAMIGNORECONSTRAINTS see install option `--ignore-constraints-on`

       OPAMIGNOREPINDEPENDS see option `--ignore-pin-depends`

       OPAMJOBS sets the maximum number of parallel workers to run.

       OPAMJSON log json output to the given file (use character `%' to index the files)

       OPAMLOCKED see install option `--locked`

       OPAMLOGS logdir sets log directory, default is a temporary directory in /tmp

       OPAMMAKECMD set the system make command to use

       OPAMNOAUTOUPGRADE disables automatic internal upgrade of repositories in an earlier format
       to the current one, on 'update' or 'init'.

       OPAMKEEPLOGS tells opam to not remove some temporary command logs and some backups. This
       skips some finalisers and may also help to get more reliable backtraces

       OPAMLOCKRETRIES sets the number of tries after which opam gives up acquiring its lock and
       fails. <= 0 means infinite wait.

       OPAMMERGEOUT merge process outputs, stderr on stdout

       OPAMNO answer no to any question asked.

       OPAMNOASPCUD Deprecated.

       OPAMNOCHECKSUMS enables option --no-checksums when available.

       OPAMNOSELFUPGRADE see option `--no-self-upgrade'.

       OPAMPINKINDAUTO sets whether version control systems should be detected when pinning to a
       local path. Enabled by default since 1.3.0.

       OPAMPRECISETRACKING fine grain tracking of directories

       OPAMREQUIRECHECKSUMS Enables option `--require-checksums' when available (e.g. for `opam

       OPAMRETRES sets the number of tries before failing downloads.

       OPAMROOT see option `--root'. This is automatically set by `opam env --root=DIR

       OPAMROOTISOK don't complain when running as root.

       OPAMSAFE see option `--safe'

       OPAMSHOW see option `--show`

       OPAMSKIPUPDATE see option `--skip-updates`

       OPAMSKIPVERSIONCHECKS bypasses some version checks. Unsafe, for compatibility testing

       OPAMSOLVERTIMEOUT change the time allowance of the solver. Default is 60.0, set to 0 for
       unlimited. Note that all solvers may not support this option.

       OPAMSTATUSLINE display a dynamic status line showing what's currently going on on the
       terminal. (one of one of `always', `never' or `auto')

       OPAMSTATS display stats at the end of command

       OPAMSTRICT fail on inconsistencies (file reading, switch import, etc.)

       OPAMSWITCH see option `--switch'. Automatically set by `opam env --switch=SWITCH

       OPAMUNLOCKBASE see install option `--unlock-base`

       OPAMUPGRADECRITERIA specifies user preferences for dependency solving when performing an
       upgrade. Overrides OPAMCRITERIA in upgrades if both are set. See also option --criteria

       OPAMUSEINTERNALSOLVER see option `--use-internal-solver'.

       OPAMUSEOPENSSL force openssl use for hash computing

       OPAMUTF8 use UTF8 characters in output (one of one of `always', `never' or `auto'). By
       default `auto', which is determined from the locale).

       OPAMUTF8MSGS use extended UTF8 characters (camels) in opam messages. Implies OPAMUTF8.
       This is set by default on OSX only.

       OPAMVALIDATIONHOOK hook if set, uses the `%{hook%}` command to validate an opam repository

       OPAMVAR_var overrides the contents of the variable var when substituting `%{var}%` strings
       in `opam` files.

       OPAMVAR_package_var overrides the contents of the variable package:var when substituting
       `%{package:var}%` strings in `opam` files.

       OPAMVERBOSE see option `--verbose'.

       OPAMWORKINGDIR see option `--working-dir`

       OPAMYES see option `--yes'.


       As an exception to the following, the `exec' command returns 127 if the command was not
       found or couldn't be executed, and the command's exit value otherwise.

       0   Success, or true for boolean queries.

       1   False. Returned when a boolean return value is expected, e.g. when running with
           --check, or for queries like opam lint.

       2   Bad command-line arguments, or command-line arguments pointing to an invalid context
           (e.g. file not following the expected format).

       5   Not found. You requested something (package, version, repository, etc.) that couldn't
           be found.

       10  Aborted. The operation required confirmation, which wasn't given.

       15  Could not acquire the locks required for the operation.

       20  There is no solution to the user request. This can be caused by asking to install two
           incompatible packages, for example.

       30  Error in package definition, or other metadata files. Using --strict raises this error
           more often.

       31  Package script error. Some package operations were unsuccessful. This may be an error
           in the packages or an incompatibility with your system. This can be a partial error.

       40  Sync error. Could not fetch some remotes from the network. This can be a partial

       50  Configuration error. Opam or system configuration doesn't allow operation, and needs

       60  Solver failure. The solver failed to return a sound answer. It can be due to a broken
           external solver, or an error in solver configuration.

       99  Internal error. Something went wrong, likely due to a bug in opam itself.

       130 User interrupt. SIGINT was received, generally due to the user pressing Ctrl-C.




       Vincent Bernardoff <>
       Raja Boujbel <>
       Roberto Di Cosmo <>
       Thomas Gazagnaire <>
       Louis Gesbert <>
       Fabrice Le Fessant <>
       Anil Madhavapeddy <>
       Guillem Rieu <>
       Ralf Treinen <>
       Frederic Tuong <>


       Check bug reports at